Download Thyroid hormones

Endocrine (hormone) System
Hendra Wijaya
Hormones are chemical
messengers secreted by
certain tissues into the
blood or institial fluid,
serving to regulate the
activity of other tissues.
Chemical Classification of Hormones
• Amine hormones are derived from tyrosine or tryptophan
– Include NE, Epi, thyroxine, melatonin
• Polypeptide/protein hormones are chains of amino acids
– Include ADH, GH, insulin, oxytocin, glucagon, ACTH, PTH
• Glycoproteins
– Long polypeptide bound to a carbohydrate group
– Include LH, FSH, TSH
• Steroids are lipids derived from cholesterol
– Include testosterone, estrogen, progesterone & cortisol
11-7
Chemical Classificaton of Hormones
• Steroid Hormones:
– Lipid soluble
– Diffuse through cell membranes
– Endocrine organs
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Adrenal cortex
Ovaries
Testes
placenta
Chemical Classification of
Hormones
• Nonsteroid Hormones:
– Not lipid soluble
– Received by receptors external to the cell
membrane
– Endocrine organs
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Thyroid gland
Parathyroid gland
Adrenal medulla
Pituitary gland
pancreas
Regulatory Systems
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Target cells~ body cells that respond to
hormones
Endocrine system/glands~ hormone
secreting system/glands (ductless);
exocrine glands secrete chemicals (sweat,
mucus, enzymes) through ducts
Neurosecretory cells~ actual cells that
secrete hormones
Feedback mechanisms ~ negative and
positive
Endocrine System
Major Endocrine Glands
1. Pineal Gland
2. Hypothalamus
3. Pituitary Gland
1. Anterior
2. Posterior
4. Thyroid Gland
5. Parathyroid
Glands
6. Adrenal Glands
6. Cortex
7. Medulla
7. Thymus Gland
8. Pancreas
9. Gonads
6. Ovaries
7. Testes
There is a hierarchical
chain of command in
hormonal signaling.
Coordination center
of the endocrine
system.
Via direct neuronal connection
Hypothalamus-pituitary axis
Feedback control
Feedback
control of
thyroid
function
Mode of Action: Chemical Signaling
• 1- Plasma membrane reception
• signal-transduction pathways (neurotransmitters, growth factors, most
hormones)
• 2- Cell nucleus reception
• steroid hormones, thyroid hormones, some local regulators
Hypothalamus
• Part of brain
– Regulates ANS,
emotions,
feeding/satiety,
thirst, body
temperature, etc.
– Hormones related to
these functions
• “Releasing hormones”
• Axonal transport to
posterior lobe
Hypotalamus
• Hypothalamus and pituitary gland secrete hormones and
regulate other endocrine organs. They are the main regulatory
organs of the endocrine system.
Hypothalamus
• Located below the
thalamus and above the
pituitary gland
(=epiphysis)
• Regulates the pituitary
gland secretions through
two different
mechanisms
Hypothalamus - neurohypophysis
• 1- Neurons, receiving
information from
receptors, fire APs
which travel down to
the post pituitary
gland and stimulate
the release of stored
neurohormones –
Oxytocin (OT) and
anti-diuretic hormone
(ADH)
Pituitary Gland
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Releasing and inhibiting hormones
Anterior pituitary:
Growth (GH)~bones
√gigantism/dwarfism
√acromegaly
Prolactin (PRL)~mammary glands;
milk production
Follicle-stimulating (FSH) &
Luteinizing (LH)~ovaries/testes
Thyroid-stimulating (TSH)~ thyroid
Adrenocorticotropic (ACTH)~
adrenal cortex
Melanocyte-stimulating (MSH)
Endorphins~natural ‘opiates’; brain
pain receptors
Hormones of the Anterior Pituitary
Hypothalamus & Pituitary Gland
Posterior Region of the Pituitary Gland
• The posterior pituitary:
• Oxytocin~
uterine and mammary gland
cell contraction
• Antidiuretic (ADH)~
retention of water by kidneys
The Pineal, Thyroid, & Parathyroid
• Melatonin~ pineal gland;
biological rhythms
• Thyroid hormones:
Calcitonin~
lowers blood calcium
Thyroxine~
metabolic processes
• Parathyroid
(PTH)~ raises blood
calcium
The thyroid gland - Chp 21 p 623-625
• Located in the neck, just below
the larynx
• Secrete 2 types of hormone:
- thyroid hormones  stimulate
cell metabolism,
triiodothyronine (T3) and
thyroxine (T4) – iodine is
needed to synthesize these
hormones
- calcitonin  decrease blood
calcium
Figure 6.8a
Thyroid hormones
• T3 and T4 secreted by
the follicular cells
• Stored as colloid
• Parafollicular cells (C
cells) secrete
calcitonin (Chp 19)
Thyroid Hormones T3 and T4
• Target organs: all cells
• Role: Increase cell metabolism, oxygen
consumption
• Permissive role for some other hormones
(growth hormone)
Thyroid hormone regulation
Figure 6.7
Goiter
• Both hypo and hyperthyroidism can have
goiter as a symptom
• Goiter is a swelling of the neck due to
hypertrophy of the thyroid gland
• How can one explain that?
Goiter in hypothyroidism
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Most often due to a lack of dietary
iodine
The thyroid hormone is unable to
synthesize a functional thyroid
hormone (T3 and T4)
The person express symptoms of
hypothyroidism
The nonfunctional T3/T4 cannot
promote a negative feedback on
TRH and TSH
 the hypotalamus and pituitary
gland increase their secretions 
the thyroid gland is stimulated to
secrete more T3 and T4 …
In children, the lack of functional
T3/T4 result in cretinism, a form a
mental retardation
Goiter in hyperthyroidism
• The cells secreting TRH or
TSH on the hypothalamus and
pituitary gland (respectively)
have become abnormal and no
longer are sensitive to the
negative feedback  they
continue to secrete TRH or
TSH  continuous stimulation
of the thyroid gland with excess
thyroid hormones being formed
•  symptoms of
hyperthyroidism
Parathyroid glands
• Four nodules located in
the back of the thyroid
gland
• Secreted parathyroid
hormone or parathormone
or PTH
• Action of PTH opposes
action of calcitonin
• Both hormones play a role
in calcium metabolism
Roles of calcium
• Most calcium ions are stored in the bones
• Calcium is an important cofactor for enzymatic activity, plays
a role in blood coagulation and action potentials.
• Calcitonin and PTH participate in calcium regulation
• Vitamin D helps PTH activity
Calcium regulation:
• Calcitonin promotes blood
calcium decrease, by:
- 1. calcium deposition on
bone
- 2. calcium dumping by the
kidney
• PTH promotes blood
calcium increase by:
- 1. bone resorption
- 2. calcium reabsorption by
kidney
- 3. increase calcium
absorption by intestine
Calcium Metabolism:
Figure 23-20: Calcium balance in the body
Figure 19.20
The Pancreas
• Islets of Langerhans
• Alpha cells:
•glucagon~ raises blood glucose levels
• Beta cells:
•insulin~ lowers blood glucose levels
• Type I diabetes mellitus
(insulin-dependent; autoimmune
disorder)
• Type II diabetes mellitus
(non-insulin-dependent; reduced
responsiveness in insulin targets)
The pancreas
• Located in the left upper
abdominal cavity
• Exocrine and endocrine
glands
• The endocrine function is
due to the cells of the
islets of the Langerhans
-- α cells  glucagon
-- β  insulin
-- δ  somatostatin
Glucose regulation
• Glucose level controlled
by insulin and glucagon
• Insulin promotes a
decrease in blood glucose
• Glucagon promotes an
increase in blood glucose
Glucose regulation
Fate of glucose
Figure 3.21
Diabetes mellitus
• Type I: autoimmune disease  beta cells of the
islets of Langerhans are destroyed by antibodies
• Type II: The cells become insulin-resistant 
glucose does not enter the cells as readily
• http://faculty.weber.edu/nokazaki/Human_Physiol
ogy/Class%20notes/diabetes.htm
The Adrenal Glands
• Adrenal medulla (catecholamines): •epinephrine & norepinephrine~
increase basal metabolic rate (blood glucose and pressure)
• Adrenal cortex (corticosteroids): •glucocorticoids (cortisol)~ raise blood
glucose •mineralocorticoids (aldosterone)~ reabsorption of Na+ and K+
The Gonads
• Steroid hormones:
precursor is cholesterol
– Androgens (testosterone)
• sperm formation
• male secondary sex characteristics; gonadotropin
– Estrogens (estradiol)
• uterine lining growth
• female secondary sex characteristics
• gonadotropin
– Progestins (progesterone)
• uterine lining growth
The Gonads
• Steroid hormones:
precursor is cholesterol
• androgens
(testosterone)~ sperm
formation; male secondary sex
characteristics; gonadotropin
• estrogens
(estradiol)~uterine lining growth;
female secondary sex
characteristics; gonadotropin
• progestins
(progesterone)~uterine lining
growth
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are needed to see this picture.
Revision: Major endocrine conditions
Endocrine
Gland
Hormones
Endocrine Disorders
Anterior Pituitary
Growth Hormone
Gigantism, acromegaly
Dwarfism
Thyroid
Thyroxine (T4)
Triodothronine
(T3)
Thyrotoxicosis
Goitre
Exopthalmos
Hypothroidism
Cretinism
Myxoedema
Goitre
Parathyroid
Parathormone
Osteoporosis
Kidney stones
Kidney stones
Tetany
Adrenal Cortex
Glucacorticoids
Cushings syndrome
Addisons disease
Adrenal Medulla
Epinephrine
Norepinephrine
Increased metabolism
Hypertension
Pancreatic Islets
Insulin
Hyper
Hypo
Diabetes mellitus
Pituitary Dwarfism
Hyper secretion of Growth hormone: Gigantism