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Topic 14:
Addendum on Thyroid Hormones
Bernard Courtois – biochemist who discovered iodine in 1811
Edward Kendall - isolated thyroxine in 1915
Parafollicular cells (also called C cells) are
cells in the thyroid that produce and secrete
calcitonin.
Cuboidal follicular cells (also called principal
cells) are cells in the thyroid gland that produce
and secrete thyroxine (T4) and triiodothyronine
(T3).
Goiter… a Thyroid
condition
A goiter (or goitre or
bronchocele) is a swelling in
the thyroid gland which can lead
to pronounced swelling in the
neck region.
Worldwide, the most common
cause for goitre is iodine
deficiency. In countries that use
iodized salt, Hashimoto's
Thyroiditis (HT) is the most
common cause.
HT is an autoimmune disease in
which the thyroid gland is
gradually destroyed by a variety
of cell and antibody mediated
immune processes. It was the
first disease to be recognized as
an autoimmune disease.
Conditions of hyperthyroidism and hypothyroidism in their various forms can also
contribute to development of goiter. Here we see a few of the many thyroidpituitary interactions that can result in hyperthyoid or hypothyroidism.
Chapter 13 Bonus Feature #2:
Predendum on Catecholamines
epinephrine
Catecholamines – various hormones that are released by the adrenal glands (and
other sites) in response to stress. They are part of the sympathetic nervous
system.
These hormones are collectively referred to as catecholamines because they
contain a catechol group, and are derived from the amino acid tyrosine.
The two primary forms we know are:
Epinephrine (E) [be careful in using this abbreviation because it is also used for
estrogen]
Norepinephrine (NE)
However, the neurotransmitter dopamine is also a catecholamine:
Dopamine (DA) - dopamine oxidation is suspected as being responsible for
symptoms of schizophrenia and may be involved in producing Parkinsonism.
Capsule
Zona
glomerulosa
Adrenal
gland
Zona
fasciculata
• Medulla
• Cortex
Zona
reticularis
Kidney
Adrenal
medulla
(a)
(b)
Stress
Short term
More prolonged
Hypothalamus
Nerve impulses
CRH (corticotropinreleasing hormone)
Spinal cord
Corticotroph
cells of
anterior
pituitary
Preganglionic
sympathetic
fibers
To target in blood
Adrenal
cortex
ACTH
Adrenal
medulla
Short-term
stress response
Catecholamines
(epinephrine
and norepinephrine)
1. Increased heart rate
2. Increased blood pressure
3. Liver converts glycogen to glucose
and releases glucose to blood
4. Dilation of bronchioles
5. Changes in blood flow patterns
leading to decreased digestive
system activity and reduced
urine output
6. Increased metabolic rate
Mineralocorticoids
Glucocorticoids
Long-term stress response
1. Retention of sodium and
water by kidneys
2. Increased blood volume
and blood pressure
1. Proteins and fats
converted to glucose
or broken down for
energy
2. Increased blood glucose
3. Suppression of immune
system
Adrenergic – having or pertaining to adrenalin (E) or (NE)
Cholinergic – having or pertaining to acetylcholine (the
most common neurotransmitter)
Exogenous substances that stimulate cholinergic
receptors include nicotine and muscarine (these
substances are called cholinomimetic agents)
Muscarine is a chemical compound found in some mushrooms, particularly a
number of inocybe and clitocybe species. It is known to be toxic.
Taxi Driver in India visiting the Coffee Shop
He is stimulating his nicotinic receptors via the hookah.
13.3 Continuum of mood from depression to mania
13.4 Cortisol secretion and depression (Part 1)
13.4 Cortisol secretion and depression (Part 2)
Dexamethasone is a potent synthetic member of the
glucocorticoid class of steroid hormones. It acts as an antiinflammatory and immunosuppressant. Its potency is about
20-30 times that of hydrocortisone and 4-5 times of
prednisone.
13.4 Cortisol secretion and depression (Part 3)
13.5 Cortisol and mood
13.6 Phototherapy may ameliorate seasonal affective disorder (SAD)
Individuals with SAD
received therapies on AM
and PM intervals.
13.7 The serotonergic synapse
13.8 Light exposure affects both onset time and level of melatonin secretion (Part 1)
N = normal
subjects…
melatonin
secretion
occurs earlier
SAD individuals
and melatonin
secretion
occurs later
prior to
treatment and
becomes
similar to N
after treatment
13.8 Light exposure affects both onset time and level of melatonin secretion (Part 2)
Higher
melatonin
levels are
associated
with less
light
exposure
(open
circles)
13.10 Outdoor light is far brighter than artificial light
13.11 Patterns of melatonin secretion in seasonal depression (Part 1)
13.11 Patterns of melatonin secretion in seasonal depression (Part 2)
Bonus Feature #3 – Effects of
Insulin on Glucose Metabolism