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Biomedicine: Human Sciences
Lecture 9:
Endocrine System
1
Learning Outcomes
In today’s topic you will learn:
 The endocrine system, it’s
structure, function and
common pathologies.
http://www.hormone.org/
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Endocrine system & hormones
The endocrine system coordinates the activity of organs through
hormones – chemical messengers released into the blood from glands
which produce them.
Hormones have specific target cells / tissues, some far from where the
hormone is produced, others effect cells of the organ where they were
released (paracrine effect), or the same cell type (autocrine effect).
Hormones can be peptides, steroids, or amino acid derivatives.
Hormones play an essential role in the bodies homeostasis, including rate
of metabolism, blood pressure, blood glucose levels, body acidity etc.
AUTONOMIC NERVOUS SYSTEM
ENDOCRINE SYSTEM
Rapid Change
Slower Change
Less Precise
More Precise
Shorter Duration
Longer Duration
Neurotransmitters
Hormones
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Glands
There are 2 types of glands:
1. EXOCRINE - excrete their products into ducts leading to the external
environment. Examples include salivary glands (saliva), gastric glands
(digestive enzymes), sebaceous glands (sebum), mammary glands
(breast milk).
2. ENDOCRINE – are ductless, they secrete their products (hormones)
into the blood or nearby target cells / tissues.
.
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Glands
Hormone:
.
from Greek hormōn, from horma
n to stir up, urge on, from hormē impulse, move.
A chemical substance produced in an endocrine
gland and transported in the blood to a certain tis
sue on which it exerts a specific effect.
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Glands
Endocrine glands include:
•
•
•
•
•
•
•
•
•
•
Hypothalamus (neuroendocrine gland)
Pituitary (glandular & neuroendocrine)
Pineal
Thyroid
Parathyroid
Adrenal
Pancreatic: islets of Langerhans
Thymus
Ovaries
Testes
http://www.hormone.org/
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Endocrine Tissues
Some tissues of the body are not considered glands but have
endocrine functionality: produce hormones:
•
•
•
•
•
•
•
Adipose tissue - leptin (suppresses food intake) & resistin (blood
glucose, inflammation).
Heart - atrial natriuretic peptide (blood pressure).
GIT: stomach - ghrelin & gastrin (satiety & gastric emptying).
Liver – angiotensinogen, Insulin-like growth factor
(IGF), thrombopoietin.
Placenta - human chorionic gonadotropin (hCG) & progesterone.
Kidneys - erythropoietin (RBC production) & calcitriol (vit. D).
Skin – cholecalciferol (vit. D).
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Hormone activity
Hormones have specific target cells – they influence the activity of the
target cells by identifying & binding to specific receptors (proteins) within or
on the surface of the target cells.
The target cells can alter their sensitivity to the hormone:
Down-regulation: with an excess quantity of hormone target cells reduce
the number of protein receptors to reduce hormone activity on the cell.
Up-regulation: a deficiency in hormone causing an increase in the number
of receptors on target cells.
Hormone secretion regulation:
1. Nervous system signals
2. Chemical changes in the blood
3. Other hormones.
They are controlled through feedback loops – positive and negative.
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Endocrine system – control
The hypothalamus is the ‘master’ endocrine gland, controlling the hormones
released from the 2 lobes of the pituitary gland: anterior & posterior.
The hypothalamus & pituitary glands together control almost entirely:
growth, development, metabolism and homeostasis.
HYPOTHALAMUS
Inhibitory
hormones
Stimulating/
releasing
hormones
Nerve
impulses
PITUITARY GLAND
hypothalamus & pituitary gland are connected by a stalk
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Pituitary gland
Posterior
• Receives nerve impulses
from the hypothalamus.
• Releases the following
hormones:
•
•
Anterior
• Receives blood from the
hypothalamus.
• Releases the following
hormones:
•
Oxytocin
Antidiuretic hormone (ADH)
•
•
•
•
•
•
•
Growth hormone (GH) /
Somatotropin
Thyroid stimulating hormone
(TSH)
Follicle stimulating hormone
(FSH)
Luteinizing hormone (LH)
Prolactin (PRL)
Adrenocorticotropic
hormone (ACTH)
Melanocyte stimulating
hormones (MSH)
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HORMONES of the HYPOTHALAMUS, ANTERIOR PITUITARY
& THEIR TARGET ORGANS / TISSUES
Growth Hormone
Releasing Hormone
Growth Hormone
Growth Hormone
Releasing Inhibiting
Hormone
Thyroid Releasing
Hormone
Corticotropin Releasing
Hormone
Prolactin Releasing
Hormone
Thyroid Stimulating
Hormone
Adrenocorticotropic
Hormone
Prolactin
Prolactin Inhibiting
Hormone
Follicle Stimulating
Hormone
Gonadotropin
Releasing Hormone
Luteinizing Hormone
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Growth hormone (GH)
Also known as somatotropin.
Growth hormone releasing
inhibiting hormone (GHRIH)
/ somatostatin.
ACTIVITY:
1. Regulates metabolism in many organs.
2. Promotes growth & division of (most) body
cells (especially bone & muscle).
3. Stimulates release of insulin-like growth
factors (IGF’s) in cells.
INCREASED PRODUCTION:
• Night (sleep)
• Hypoglycaemia
• Exercise
• Anxiety
• Childhood & adolescence
Growth hormone releasing hormone (GHRH).
Growth hormone /
somatotropin
ALL TISSUES
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Thyroid Stimulating Hormone (TSH)
ACTIVITY:
1. Growth & activity of the thyroid gland:
increasing thyroid hormone production thyroxine (T4) & tri-iodothyronine (T3).
PRODUCTION:
• Lowest levels in the early evening & highest
during the night.
Thyroid releasing hormone (TRH)
TSH
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Adrenocorticotropic hormone (ACTH)
High ACTH levels
ACTIVITY:
1. Circadian rhythm (sleep / wake cycle)
2. Output of steroid hormones:
glucocorticoids, especially cortisol.
INCREASED PRODUCTION:
• Hypoglycaemia
• Exercise
• Stressors such as emotions, fever
• Interleukin-1
Corticotropin releasing hormone (CRH)
Adrenocorticotropic hormone (ACTH) /
corticotrophin
ADRENAL COTREX
PRODUCTION:
• Highest in the morning and lowest at
midnight.
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Prolactin (PRL)
ACTIVITY:
1. Stimulates lactation (together with other
hormones)
2. Prevents pregnancy during lactation.
3. Breast maturation after childbirth.
PRODUCTION:
• After birth
• Suckling
• Emotional stress
• Sleep (at any time of day)
Prolactin releasing hormone (PRH)
Prolactin
MAMMARY
GLANDS
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Follicle stimulating hormone
(FSH) & luteinizing hormone (LH)
ACTIVITY:
• FSH:
•
•
•
•
•
High levels of:
• Oestrogen,
• Progesterone
• Testosterone
Production of gametes (male & female)
Increase oestrogen production (F)
Maturation of ovarian follicles (F)
Stimulate testosterone production (M)
Sperm production (M)
• LH
•
•
•
Triggers ovulation & formation of corpus luteum
Increase secretion of progesterone (F)
Stimulates secretion of testosterone (M)
Gonadotropin releasing hormone (GnRH)
Follicle stimulating
hormone (FSH)
Luteinizing hormone
(LH)
OVARIES & TESTES
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Melanocyte Stimulating Hormone (MSH)
• Produced by the anterior pituitary
• Fx
• Increases skin pigmentation in
amphibians. Exact role in humans is
unknown but MSH can be erroneous
produced as part of some pathologies
• Stimulated by: Corticotrophin releasing
hormone
• Inhibited by: Prolaction inhibiting
hormone (dopamine)
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Oxytocin
ACTIVITY:
1. Contracts uterus in childbirth (parturition)
2. Contracts lactating breast
3. Bonding hormone (mother with baby)
Nerve Impulses
(no stimulation)
PRODUCTION:
• Suckling
• Childbirth
• POSITIVE FEEDBACK
Posterior pituitary
OXYTOCIN
Mammary glands & muscles
Uterine Muscles
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Antidiuretic hormone (ADH)
Also known as vasopressin.
ACTIVITY:
1. Reduces urine output by stimulating
reabsorption sodium & water in the kidneys.
2. Vasoconstriction in skin & abdominal
organs to increase blood pressure,
preventing hypovolaemic shock.
PRODUCTION:
• ADH production: increased osmotic
pressure, reduced fluid intake.
• ADH production inhibited by: reduced
osmotic pressure, increased fluid intake,
alcohol.
Hypothalamic
Osmoreceptors
Nerve Impulses
Posterior lobe of
pituitary gland
ADH
Kidneys
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Antidiuretic hormone (ADH)
Decreased
reabsorption
of urine
(increased
elimination)
Osmoreceptors
In Hypothalamus
Indicate High
Osmotic Pressure
(Not enough
fluid)
ADH
Secretion
Suppressed/
Inhibited
ADH
Secretion
Stimulated
Osmoreceptors
In Hypothalamus
Indicate Low
Osmotic
Pressure
(Too much fluid)
Increased
reabsorption
of urine &
Vasoconstriction
(decreased
urination)
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Pituitary gland pathologies
Usually caused by autoimmune disease or tumours causing either:
• Hyper-secretion
• Hypo-secretion
Signs & symptoms depend on the hormones affected.
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Acromegaly & gigantism
Acromegaly: excess growth hormone (GH) after ossification (bone formation) leading to the
excess growth of body tissues over time.
Gigantism: excess growth hormone (GH) while the bones are still growing.
CAUSES:
Usually a pituitary tumour causing hyper-secretion & damage to the optic nerve.
SIGNS & SYMPTOMS (Sx):
Large, prominent facial features, increased size of hands & feet - spade like hands & feet,
headaches, excessive sweating, large tongue, oedema, tiredness, deep voice, impotence,
joint pain, little bony deformities, soft-tissue swellings. Gigantism: giant-like features because
the WHOLE body is able to grow.
TREATMENT (Rx):
Surgery to remove cancer, reduce GH levels to normal.
ALTERNATIVE SUPPORT (Rx):
Treat / support cause. Herbs & nutritional supplements – antioxidants, diet is essential for all
forms of cancer (primarily plant based diet rich in nutrients & antioxidants), alkalising the
body.
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Acromegaly & gigantism
COMPLICATIONS:
If left untreated can be serious, even fatal: type 2 diabetes, hypertension,
cardiovascular disease, arthritis, bowel polyps (may become cancerous).
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Hyperprolactinaemia
Excess prolactin production.
CAUSES:
Tumour on the pituitary, acromegaly, PCOS,
hypothyroidism.
SIGNS & SYMPTOMS (Sx):
Galactorrhoea, amenorrhoea / oligomenorrhoea,
decreased libido (both male & female), subfertility.
ALTERNATIVE SUPPORT (Rx):
Treat / support the cause. Herbs can help
balance hormone levels in cases of hypothyroid
& PCOS. Nutrition to support thyroid function. In
cases of cancer – antioxidants, diet (primarily
plant based diet rich in nutrients & antioxidants),
alkalising, acupuncture, homeopathy.
http://www.rayur.com
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Diabetes insipidus
ADH deficiency causing the kidneys to allow over excretion of water from the
body.
CAUSES:
Usually brain trauma, tumour, encephalitis (inflammation of the brain).
SIGNS & SYMPTOMS (Sx):
Extreme thirst & urination - large quantities often, 4-5 L of liquid may be
consumed daily.
TREATMENT (Rx):
Treat cause. Rehydration: water & electrolytes,
homeopathy, acupuncture.
.
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Pineal gland - Melatonin
A small pine-cone shaped gland in the midline of the brain under control by the
hypothalamus.
It produces the hormone melatonin.
ACTIVITY:
Contribute to the setting of the circadian rhythm.
A potent antioxidant.
Atrophy of gonads & may play a role in the onset
of puberty & inhibiting reproduction with increasing age.
PRODUCTION:
Made from serotonin.
Levels are highest in children & decline with age.
Stimulated by: night, darkness.
Reduced by: daylight, irregular sleep patterns (jetlag, night-work), some
medications.
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Thymus gland - Thymosin
A bi-lobed gland behind the sternum which plays an important role with immune
cells.
It atrophies with age.
ACTIVITY:
Site of maturation of T-cells of the immune system.
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Thyroid gland
A butterfly shaped gland inferior to the larynx. It has 2 lobes
located on either side of the trachea.
Follicular cells produce thyroid hormones:
thyroxine (T4) & triiodothyronine (T3)
Parafollicular cells produce calcitonin (CT).
Production begins in the 3rd month of development in the
foetus.
T4 & T3 are synthesized from tyrosine & iodine within a
specialized thyroid protein called thyroglobulin (Tg).
T4 has 4 iodine atoms, T3 contains 3 iodine atoms.
Follicular cells trap & store most of the bodies iodide
(approx. 100 day supply).
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Thyroid gland - Thyroxine
The major form of thyroid hormone in the blood is thyroxine (ratio of T4 to T3
is approx. 20:1).
Selenium-containing enzymes are used in the conversion of T 4 to T3.
T3 is a more biologically active form, being 3 to 4 times more potent than T4.
T4 & T3 are hydrophobic and require carrier proteins in the blood: thyroxinebinding globulin (TBG). This prevents these hormones from entering parts
of the body that don't require thyroid hormones & allows the body to
maintain a stable pool of thyroid hormones from which the active, free
hormones can be released when & where required.
Thyroid hormone levels must therefore be measured in terms of free T4 &
T3.
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Thyroid gland - Thyroxine
ACTIVITY:
Increase metabolic rate & heat production.
Essential for normal growth / development.
Central nervous system (CNS) function.
Work in conjunction, & enhance, the activities of
adrenalin (epinephrine) & noradrenaline
(norepinephrine), insulin & hGH.
PRODUCTION:
Stimulated by: TSH, exercise, stress, malnutrition,
low blood glucose, low T3 to T4.
Reduced by: low TSH, high T3 to T4.
Highest levels at night.
Higher levels during adolescence, pregnancy &
female reproductive years.
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T3, T4 & TSH Levels
Low Plasma Glucose, Stress, Exercise, Sleep, Malnutrition
Stimulates Hypothalamus
•
If TSH
levels are
RAISED
this
indicates
that the
Thyroid is
FAILING
•
TSH is
usually
LOW in a
Thyroid Releasing Hormone
(TRH)
Decreases
TRH
secretion
Stimulates Anterior
Pituitary
Thyroid Stimulating Hormone
(TSH)
Decreases
Pituitary
sensitivity to
TRH
Stimulates Thyroid
↑ Thyroxine (T4)
↑ Tri-iodothyronine (T3)
REGULARLY
functioning
Thyroid
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Thyroid gland - Thyroxine
LAB TESTS:
1. TSH Levels.
2. Free T3 & T4 - unbound form of thyroid hormones are the more
bioavailable by the target cells & tissues.
3. Thyroglobulin (Tg) - levels in the blood can be used as a tumour marker
for certain kinds of thyroid cancer.
4. Anti-thyroglobulin antibodies (ATA), frequently referred to as TgAb, are
often found in patients with Hashimoto's thyroiditis or Graves' disease,
although may be present in healthy individuals (can be destructive or
stimulating & may co-exist).
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Hypothyroidism
Is a condition of thyroid hormone deficiency, common in the elderly.
CAUSES:
Autoimmune - hashimoto’s thyroiditis, iodine deficiency, thyroid destruction
(radioactive iodine, surgery, side-effects of medication e.g. lithium,
congenital, tumour (thyroid / hypothalamic, pituitary).
SIGNS & SYMPTOMS (Sx):
Tiredness, malaise, weight gain, goitre, anorexia, cold intolerance, poor
memory, mental slowness, goitre, puffy around the eyes (myxoedema),
depression, mood swings, low libido, dry brittle hair / skin, muscle cramps,
arthralgia, constipation, psychosis, menorrhagia or oligomenorrhoea, loss of
eyebrows, slow reflexes, deep voice, bradycardia and hypertension.
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Hypothyroidism
ALLOPATHIC TREATMENT: Levothyroxine – thyroid
hormone replacement
ALTERNATIVE SUPPORT (Rx):
Cause. Thyroid support: iodine, selenium, tyrosine,
thyroid replacement therapy. Herbs to support thyroid.
Herbs to support tumour or autoimmune condition.
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Hyperthyroidism (Grave's disease)
Hyperthyroidism (also known as thyrotoxicosis) is characterised by hypermetabolism and elevated serum levels of free thyroid hormones.
CAUSES:
Graves disease (most common cause): autoimmune condition - IgG antibodies
bind to TSH receptor and stimulate production of thyroid hormones, excessive
intake of iodine or thyroid hormone, tumour (hypothalamic, pituitary), thyroiditis,
nodule.
SIGNS & SYMPTOMS (Sx):
Nervousness, palpitations, hyperactivity, increased sweating, heat hypersensitivity,
fatigue, increased appetite, weight loss, insomnia, weakness, frequent bowel
movements, warm, moist skin, tremor, tachycardia, atrial fibrillation, and
palpitations.
ALLOPATHIC TREATMENT (Rx):
Drugs: antithyroid, radioactive iodine, β-Blockers, surgery.
35
Hyperthyroidism (Grave's disease)
ALTERNATIVE SUPPORT (Rx):
Treat cause. In the case of Grave’s disease herbs &
nutritional supplements to restore immune system
balance, homeopathy.
COMPLICATIONS:
Thyrotoxic crisis: hyperthermia (> 40°C / 104°Fahrenheit),
tachycardia, heart failure.
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Barnes Temperature Test
1. Prepare the thermometer before going to bed.
2. On waking, before getting out of bed, with as little movement as possible,
place the thermometer under your arm.
3. Leave it in position for 10 minutes.
4. Test for 5 consecutive days and make a note of the 3 lowest readings. If
menstruating do the test starting the second day of menses.
5. 36.6 - 36.8OC (97.8 - 98.2OF) is normal.
Below 36.6OC (97.8OF) is below normal, and may indicate hypothyroid.
Seeing a GP is recommended.
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Thyroid gland – Calcitonin
Produced by the parafollicular cells of the thyroid
gland.
ACTIVITY:
Reduces blood calcium (Ca) by: inhibiting Ca
reabsorption from the bone & kidneys, inhibiting
osteoclast activity, opposing parathyroid activity.
Important during childhood for bone growth.
PRODUCTION:
Stimulated by: increased blood Ca levels.
Inhibited by: reduced blood Ca levels.
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Parathyroid Glands
Four small glands located posteriorly to the thyroid.
Produces parathyroid hormone.
http://www.parathyroidglands.com
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Parathyroid hormone (PTH)
ACTIVITY:
Increase blood Ca when low by:
Increase Ca absorption from intestines.
Increase Ca reabsorption in bone & kidney.
Increase osteoclast activity.
Increase production of active vit. D, which increases
Ca & P absorption of the GIT.
Regulates magnesium & phosphate blood levels.
PRODUCTION:
Stimulated by: reduced blood Ca levels.
Inhibited by: increased blood Ca levels.
Blood calcium allows is essential for muscle
contraction, nerve transmission, blood clotting.
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Hyperparathyroidism
Hyperparathyroidism is characterised by hyper-metabolism and
elevated serum levels of parathyroid hormone (PTH).
CAUSES:
Usually tumours.
SIGNS & SYMPTOMS (Sx):
Often no / few symptoms, hypercalcaemia, increased risk of kidney
stone formation, osteoporosis / osteopenia, low energy, depression,
in some cases: nausea, vomiting, constipation, anorexia, muscle
paralysis.
TREATMENT (Rx):
Surgery to remove some or all of the parathyroid glands. Surgery
may include implanting parathyroid tissue into the forearm muscle to
provide residual parathyroid function.
ALTERNATIVE SUPPORT (Rx):
Herbs & nutritional supplements – antioxidants, primarily plant based
diet rich in nutrients & antioxidants), alkalising the body.
http://www.aafp.org/
41
Hypoparathyroidism
Hypoparathyroidism is characterised by hypo-metabolism and reduced
serum levels of parathyroid hormone (PTH).
CAUSES:
Usually surgery or radiation (while treating thyroid).
SIGNS & SYMPTOMS (Sx):
Hypocalcaemia, muscle cramps & spasms (called tetany), tingling lips,
fingers, and toes, pain in the face, legs, and feet, abdominal pain, dry hair,
brittle nails, dry scaly skin, cataracts, weakened tooth enamel (in children).
TREATMENT (Rx):
Calcium and vitamin D. Hormone replacement is being developed.
42
Adrenal Glands
Pair of glands superior to the kidneys.
Two parts:
• Inner medulla: part of the autonomic NS, producing:
•
•
Adrenaline (epinephrine)
Noradrenaline (norepinephrine)
• Outer cortex – produces 3 groups of steroid hormones:
•
•
•
Glucocorticoids (primarily cortisol)
Mineral corticoids (primarily aldosterone)
Sex hormones (primarily androgens)
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Glucocorticoids
Steroid hormones produced in the adrenal cortex which regulate
metabolism & resistance to stress. They include:
1. Cortisol / hydrocortisone (most abundant: about 95%).
2. Cortisone
3. Corticosterone
ACTIVITY:
1. Stimulating gluconeogenesis
2. Proteolysis (amino acids from protein)
3. Lipolysis
4. Production of glucose by the liver
5. Reduce immune response
6. Weak reabsorption of sodium & water from kidney tubules.
7. Anti-inflammatory – hence therapeutic use of steroids
44
Mineral corticoids
Primarily aldosterone.
ACTIVITY: maintenance of water / electrolyte balance:1. Reabsorption of Na in renal tubules
2. Excretion of K in urine
3. All cause retention of water to regulate blood volume and blood pressure
4. Removal of acid from the body.
PRODUCTION:
Stimulated by: angiotensin, high blood K.
Inhibited by: low blood K.
45
Sex hormones
Primarily androgens in the form of DHEA.
ACTIVITY:
1. Production of pubic & axillary hair
2. Growth (pre-pubertal)
3. Production / converted to oestrogen (in females)
PRODUCTION:
Not fully understood.
Cortical androgens are insignificant compared to amount produced in the
ovaries & testes during puberty and adulthood.
Important only at pre-pubescent and post-menopausal stages of life.
46
Adrenaline & Noradrenaline
Adrenaline (80%) & noradrenaline (20%) are produced in uneven quantities by the adrenal
medulla.
ACTIVITY:
The function of these hormones is to intensify the sympathetic response:
1. Increase heart rate & contraction causing an increase in blood pressure.
2. Increase blood flow to the heart, brain, skeletal muscles & adipose tissue.
3. Increase metabolism.
4. Increase blood glucose & triglycerides (for metabolism)
5. Decrease blood to digestion & skin.
6. Dilate pupils & airways.
Adrenaline has greater influence on the heart.
Noradrenaline effects blood vessel
PRODUCTION:
Stimulated by: exercise, fasting, shock, elevated
temperature, infection, disease, emotional stress.
Inhibited by: eating, sleeping, calmness.
47
Adrenal glands – medulla:
adrenaline & noradrenaline
.
48
Cushing syndrome / disease
Chronic high blood levels of cortisol or related corticosteroids.
Cushing syndrome is a cortisol excess from any cause, Cushing
disease is hyperfunction of the adrenal cortex from pituitary ACTH
excess.
CAUSES:
Hyperfunction of the adrenal cortex can be ACTH dependent or
ACTH independent: hypersecretion of ACTH by the pituitary gland,
carcinoma of pituitary or adrenals, administration of exogenous
ACTH.
SIGNS & SYMPTOMS (Sx):
Central weight gain, depression, insomnia, psychosis, amenorrhoea,
poor libido, thin skin, easy bruising, reduced immunity, muscular
weakness, growth arrest in children, back pain, moon face, buffalo
hump, bone fractures, osteoporosis, insulin resistance, hirsutism,
hypertension.
49
Cushing syndrome / disease
TREATMENT (Rx):
Drugs inhibiting cortisol production, surgery (for cancer).
ALTERNATIVE SUPPORT (Rx):
Treat cause with herbs, homeopathy & nutritional supplements if indicated
(cancer support).
COMPLICATIONS:
Lowered immunity, paper skin, bone fractures.
50
Addison’s disease
An insidious, usually progressive hypo-functioning of the adrenal cortex causing
mineralocorticoids (Na reabsorption and K excretion) and glucocorticoids (blood
glucose & metabolism) to be deficient.
CAUSES:
Atrophy of the adrenal gland often due to auto-immune destruction but may be
from other causes such as disease, abrupt cessation of steroid medications.
SIGNS & SYMPTOMS (Sx):
Weakness, fatigue, and hypotension are early signs. Hyperpigmentation, black
freckles, weight loss, anorexia, malaise, weakness, fever, depression, impotence /
amenorrhoea, muscle fatigue, low blood pressure, syncope, nausea / vomiting,
confusion, diarrhoea, cravings for salty foods, abdominal pain, myalgia, joint pain,
loss of body hair, dehydration.
TREATMENT (Rx):
Hormone replacement.
51
Addison’s Disease
Adrenal failure leads to lack of
adrenal hormone production and a
failure of the normal negative
feedback mechanism.
This leads to the hypothalamus
production an excess of
corticotrophin releasing hormone
which causes the pituitary to
erroneously produce melanocyte
stimulating hormone.
This causes the skin colour to
darken, hence hyperpigmentation
Hypothalamus
CRH
Pituitary
MSH
Skin Pigmentation
ACTH
Adrenals
52
Adrenal glands – pathologies:
Addison’s disease
ALTERNATIVE SUPPORT (Rx):
Treat the cause. Herbs to support autoimmunity, homeopathy.
COMPLICATIONS:
May experience adrenal crisis when under stress (e.g. surgery, infection, illness):
asthenia; severe pain, peripheral vascular collapse, renal shutdown, severe fever.
53
http://www.medicalassessment.com/
Pancreas
The pancreas has both endocrine &
exocrine function:
endocrine function is via the cells called
the islets of Langerhans.
Three types of endocrine cells:
1. Alpha cells: produce glucagon.
2. Beta cells: produce insulin.
3. Delta cells: produce somatostatin /
GHRIH.
Main endocrine function of the pancreas is
to regulate blood glucose levels & maintain
within normal range
(4-7mmol/L).
54
Pancreas - Insulin
The first protein to have it’s amino acid sequence
identified.
ACTIVITY:
Lowers blood glucose levels, amino acids & fatty
acids.
Stimulates cells to up-take glucose from the blood.
Promotes synthesis of proteins, glycogen
(glycogenesis) & fats (lipogenesis).
PRODUCTION:
Stimulated by: high blood glucose, elevated
blood amino acids, eating, sweet taste (artificial
sweeteners).
Reduced by: low blood glucose, starvation,
glucagon.
55
Pancreas - Glucagon
ACTIVITY:
Raises blood glucose levels.
Converts glycogen to glucose in liver and skeletal
muscle: glycogenolysis & gluconeogenesis.
Lipolysis for use in metabolism.
PRODUCTION:
Stimulated by: low blood sugar, exercise.
Reduced by: insulin, high blood sugar.
56
Pancreas - Somatostatin (GHRIH)
Growth hormone releasing inhibiting hormone
Also produced by the hypothalamus & digestive
system e.g. stomach & intestines.
ACTIVITY:
Inhibits insulin & glucagon.
PRODUCTION:
Stimulated by: low blood sugar, exercise.
Reduced by: insulin, high blood sugar.
57
Diabetes
A metabolic disorder characterized by a deficiency / absence of insulin due to impaired
production or resistance causing a disruption of carbohydrate & fat metabolism & elevated
blood glucose levels: HYPERGLYCAEMIA.
TYPES:
• Type I: autoimmune
• Type II: insulin resistance
• Secondary: due to certain medications (cortisone, some diuretics), pancreatitis,
hormone disorders (high GH, thyroid hormone, cortisol, adrenaline.
• Gestational: during pregnancy as a result of placental hormones blocking Insulin action
in the mother. Usually disappears after delivery, and returns as Type 2 years later.
58
Type I diabetes
Previously called juvenile-onset or insulin-dependent (IDDM).
CAUSES:
An auto-immune condition causing destruction of pancreatic ß-cells possibly due to
an environmental exposure in genetically susceptible people: viruses (coxsackie,
rubella, cytomegalovirus, Epstein-Barr, and retroviruses) have been linked, diet exposure of infants to dairy products (especially cow's milk and the milk protein β
casein), nitrates, low vit. D consumption, early exposure to gluten and cereals
increases islet cell autoantibody production.
SIGNS & SYMPTOMS (Sx):
Glycosuria, polyuria, polydipsia, dehydration causing weakness, fatigue, and mental
status changes, weight loss, nausea and vomiting, blurred vision, predisposition to
infections, ketoacidosis: lethargy, hypotensive, tachycardia, breathe rapidly and
deeply, fruity breath due to exhaled acetone, coma.
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Type I diabetes
TREATMENT (Rx):
Insulin.
ALTERNATIVE SUPPORT (Rx):
Herbs (support pancreas, insulin sensitivity), nutrition (low GI & GL, antioxidants,
fibre, chromium, vit. D, magnesium rich foods, zinc), alkalising the body,
homeopathy and acupuncture.
COMPLICATIONS:
Increased risk of heart disease,
vascular disease, neuropathy,
retinopathy, high cholesterol,
hypertension.
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Type II diabetes
A milder form of diabetes, previously called adult-onset or non–insulin-dependent, whereby
insulin secretion is inadequate because patients have developed resistance to insulin.
hyperglycaemia develops when insulin secretion can no longer compensate for insulin
resistance. Up to one third of adults over 65 have impaired glucose tolerance. It is becoming
increasingly common among children.
CAUSES:
Clear genetic link: strong hereditary link and a high prevalence in American Indians,
Hispanics, and Asians, β-cell dysfunction and impaired insulin secretion, obesity & weight
gain, diet, exercise, and lifestyle, low birth weight, pregnancy causes some insulin
resistance.
SIGNS & SYMPTOMS (Sx):
Often asymptomatic because of mild hyperglycaemia (unlike in type I diabetes), initial
symptoms are often complications, indicating the disease has been present for some time,
ketoacidosis in severe cases.
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Type II diabetes
CONVENTIONAL TREATMENT (Rx):
Diet (low GI & GL), exercise, oral antihyperglycaemics, insulin, or both. To prevent
complications: ACE inhibitors, statins, and aspirin.
ALTERNATIVE SUPPORT:
Diet, exercise, weight loss, chromium, Herb - Gymnema, Cinnamon, vit. D
COMPLICATIONS:
Increased risk of heart disease, vascular disease, neuropathy, retinopathy, high cholesterol,
hypertension.
DIAGNOSIS:
Fasting / random blood glucose test
Oral glucose tolerance test
Urine test
.
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Ketoacidosis
Ketones are acidic, toxic, by-products of metabolising fats & proteins for energy when
carbohydrates (glucose & glycogen) levels are depleted OR when cells are unable to utilise
available glucose, as in diabetes.
Tests:
Ketones in urine (urine stick test)
Increased thirst (kidneys flush out ketones)
Breath smells fruity (acetone)
Ketoacidosis may cause coma and death.
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Diabetics Symptoms
HYPERGLYCAEMIA
HYPOGLYCAEMIA
Need for frequent urination
Shaking & sweating
Extreme hunger and / or thirst
Extreme hunger & irritability
Blurred vision
Tachycardia
Drowsiness
Dizziness, headache
Nausea
Anxiety / confusion, weak & tired
Ketoacidosis, coma
Ketoacidosis, seizures, coma, death
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Diabetic Coma
Aetiology/
pathophysiology
Differential
diagnosis
Rx / First Aid:
HYPERGLYCAEMIC
HYPOGLYCAEMIC
COMA
COMA
• Lack of insulin
• Dehydration
• Acidosis due to build up of
ketones
• Elevated blood glucose
If coma, smell breath.
Hyperglycaemic coma will
often smell like nail varnish
remover
• If conscious- water
• If in coma - 999
• Too much Insulin
• Too much exercise
• Delayed meal
May or may not have ketone
smell
• Sugar
• If in coma - 999
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Local hormones
Hormone
Secreted by
Action
Histamine
Basophils, mast cells Part of inflammation – vasodilatation and increased
blood vessel permeability
Prostaglandins,
leukotrienes &
thromboxane's
Most tissues
Chemical messengers involved in many different body
processes
Serotonin
Platelets, brain,
intestinal wall
Blood clotting, temperature regulation, appetite, sleep
Dopamine
Primarily brain
Muscle tone and some movements
Erythropoietin
Kidneys
Red blood cell production
Gastrin
GI tract
Promotes gastric juice secretion and stomach motility
Secretin
GI tract
Stimulates bile and pancreatic juice secretion
CCK
GI tract
Stimulates bile & pancreatic juice secretion.
Promotes a sense of fullness after meals
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Endocrine system & homeostasis
Whole body:
The endocrine system regulates growth and activities of cells
throughout the body e.g. glucose uptake and metabolism.
Integumentary system:
• Androgens stimulate pubic hair growth and sebaceous gland
activation.
• Melanocyte-stimulating hormone (MSH) causes skin darkening.
Skeletal system:
• Growth hormone and insulin like growth factors stimulate bone
growth.
• Oestrogen helps maintain bone mass.
• Parathyroid hormone (PTH) and calcitonin regulate calcium
levels in the bone and blood.
• Thyroid hormones are needed for development and growth of
the skeleton.
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Endocrine system & homeostasis
Muscular system:
• Adrenal hormones help increase blood flow to exercising
muscles.
• PTH helps maintain calcium levels needed for proper muscle
contraction.
• Glucagon, insulin and other hormones regulate muscle
metabolism.
• Growth hormone, Insulin like growth factors and thyroid
hormones help maintain muscle mass.
Nervous system:
• Thyroid hormones, insulin and growth hormones regulate
nervous system development.
• PTH maintains proper calcium levels needed for nervous
impulses.
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Endocrine system & homeostasis
Lymphatic system:
• Glucocorticoids depress immune response and inflammation.
• Thymus hormones promote T-cell maturation.
Cardiovascular system:
• Erythropoietin promotes formation of RBCs.
• Aldosterone and antidiuretic hormone (ADH) increase blood
volume.
• Adrenaline and noradrenalin increase heart rate and contraction
force.
Respiratory system:
• Adrenaline and noradrenalin dilate airways during exercise and
stress.
• Erythropoietin regulates amount of oxygen carried in the blood
by adjusting the number of RBCs.
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Endocrine system & homeostasis
Digestive system:
• Adrenaline and noradrenalin depress digestion.
• Gastrin, CCK and secretin help regulate digestion.
Urinary system:
• ADH and aldosterone adjust rate of water and electrolyte loss to
regulate blood volume.
Reproductive system:
• FSH and LH regulate development growth and secretions of the
ovaries and testes.
• Oestrogen and testosterone stimulate sex cell development and
changes during puberty.
• Prolactin promotes milk secretion from the mammary glands.
• Oxytocin causes contraction of the uterus and ejection of milk
from the mammary glands.
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Activity
• Complete the Endocrine System Practice Quiz and
Exercises.
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ACTIVITY
Have a look at the glossary for this topic (on the student
website).
Please also look at the prefixes & suffixes to help you
understand the medical terminology used in this lecture.
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