Topic 14 Addendum on Thyroid Hormones Bernard Courtois

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 (T 4) and triiodothyronine (T 3).

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 Spinal cord CRH (corticotropinreleasing hormone) 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