Chapter 7 - Thyroid Flashcards
What is thought to be the reason for the increase in thyroid conditions nationwide?
Chemicals used in everyday products
What overlying general concept is largely controlled by the thyroid?
Metabolism (Basal metabolic rate)
What does the thyroid regulate?
Digestion, oxygen, mobilization of fat from storage cells, body temperature
What does the thyroid control in children?
Growth, intellect, somatostatin
Thyroid hormones are what kind of hormones and are derived from what amino acid?
Amine hormones derived from tyrosine
What kind of cells make up the thyroid gland?
Follicle cells
What part of the thyroid cell pumps iodide into the cell?
Basal membrane
What is used to transport one iodide for every two sodium ions in the thyroid?
Sodium-iodide symporter
What is the first stage of the iodide process of the thyroid gland?
Sodium-iodide symporter
What is iodide trapping of the thyroid?
Process of concentrating the iodide
What influences the rate at which iodide is trapped by the thyroid gland?
TSH from the anterior pituitary gland
What enzymes promote the oxidation of iodine?
Peroxidase and hydrogen peroxide
Oxidized iodides join with what substance in the thyroid?
Thyroglobulin
Oxidized iodine binds directly with what substance to produce monoiodotryosine and diiosotyrosine?
Tyrosine
What is the major hormonal product of the coupling reaction during the iodine process of the thyroid gland?
Thyroxine (T4) and triiodothyronine (T3)
Thyroxine and triiodothyronine are cleaved from what substance?
Thyroglobulin
When are thyroxine and triiodothyronine cleaved from thyroglobulin?
When stimulated by TSH from the pituitary gland
How does the cleaving occur in the thyroid tissue?
Pinocytosis by the enlargement of follicle cells and their pseudopod formation
What thyroid hormone makes up the majority that is released into the bloodstream?
Thyroxine (T4)
What percentage of thyroxine is deiodinated to form additional triiodothyronine?
50%
Do thyroid hormones have a slow or fast onset?
Extremely slow
What is the primary function of the thyroid gland in children?
Increase in linear height
The thyroid gland stimulates the activity of what bone cells in children?
Osteoblasts (think increase in linear height)
The thyroid gland stimulates the secretion of what “growth” hormones?
Somatotrophin and insulin-like growth factor 1
What is the primary means of the thyroid gland in adults and children?
Most powerful to increase metabolism
Increase energy
What is the secondary function of the thyroid gland?
Stimulates the neuromuscular system
How does the thyroid gland affect the cell membrane permeability of certain ions?
Increases it to sodium and potassium
What effect does the thyroid gland have on neurotransmitters?
Increased synthesis and increased numbers of receptors for them (also decreases enzymes that catabolize neurotransmitters)
How does the thyroid affect the muscular system?
Stimulate the enzymes of protein anabolism
Release calcium along T-tubules of smooth and skeletal muscle
Control contractile velocity of cardiac muscle
What effect does the thyroid have on cardiac muscle?
Stimulate myosin heavy chain alpha and inhibits myosin heavy chain beta
How does the thyroid gland affect the cardiovascular system?
Heart rate and stroke volume
How does the thyroid stimulate the respiratory system?
Stimulates the enzymes of catabolism which releases CO2, release of calcium at T-tubules (flucuating thyroxine can lead to difficulty breathing)
What effect does the thyroid have on blood glucose levels?
Increases it: Increases glucagon secretion Stimulates enzymes of CHO catabolism Increases cortisol secretion Excess stimulates enzymes of protein catabolism
What effect does the thyroid gland have on plasma calcium?
Increase
How does the thyroid gland affect blood pressure?
Can become high due to increases in heart rate and/or increase in stroke volume
Can become low due to catabolism of cardiac muscle (high thyroxine)
What effect does the thyroid gland have on the pancreas?
Stimulation (increases the enzymes of digestion)
What hormones are stimulated by the thyroid gland?
Glucagon, secretin, gastrin
What effect does the thyroid gland have on the adrenal gland (overall endocrine glands too)?
Stimulation (increased secretion of cortisol through corticotropin)
What is stimulated by the thyroid gland to stimulate tissue oxygenation?
Increase secretion of erythropoietin (2,3 DPG enzyme that frees oxygen from RBCs)
What effect does the thyroid gland have on the integumentary system?
Stimulates the production of skin, hair, and nails
How does the thyroid gland increase the immune response?
Increases numbers of B and T lymphocytes
How does the thyroid gland stimulate the reproductive system?
Increased or decreased production of sex hormones (fertility vs sterility)
Production of gametes
What effect does decreased thyroxine have on the menstrual flow?
Increased
What controls the secretion of thyroid releasing factor?
Hypothalamic factor
What controls the secretion of TSH?
Adenohypophysis
What neurotransmitter can act as a hormone that decreases TSH and thyroxine?
Dopamine
What effect does estrogen have on TRF and TSH?
Increase
What effect does hCG have on TRF and TSH?
Increase
What substances are considered to be antithyroid?
Iodine in excess
Lithium
Some natural foods
What substance stimulates antibodies by way of thyroxine?
Thyroid stimulating immunoglobulin (TSI)
What is the antibody that stimulates thyroxine?
Long acting thyroid stimulator (LATS)
Excess of what substance can block the iodine?
Fluoride
