Hypothalamic-Adrenal-Pituitary, Thyroid Hormones Flashcards
what are the 6 main hormones made in the anterior pituitary (adenohypophysis)?
TSH, ACTH, FSH, LH, GH, and prolactin
what does TSH target and where made?
Thyroid stimulating hormone; made in anterior pituitary, targets the thyroid
what promotes the production of TSH?
thyrotropin releasing hormone produced in hypothalamus
what two main hormones are produced in the posterior pituitary (neurohypophysis)?
oxytocin, and ADH (antidiuretic hormone aka vasopressin)
what controls secretion of hormones from the pituitary?
releasing or inhibiting hormones made in the hypothalamus
what hormones are produced in the hypothalamus that affect the pituitary?
CRH - corticotropin releasing hormone; TRH- thyrotropin releasing hormone; GH-releasing hormone; somatostatin (GH inhibitor); Gn-RH (gonadotropin releasing) and PRL-inhibiting factor which is actually dopamine
what is the function of LH?
luteinizing hormone in females: induces ovulation and ovarian secretion of estrogen and progesterone males: stims testes to produce androgens
function of FSH
females: promotes egg development and secretion of estrogen males: supports sperm production, stims secretion of testosterone
function of TSH
stims thyroid to produce T3/T4
what will be the relative concentrations of TSH, T3 and T4 in primary vs secondary hypothyroidism?
primary: increased TSH, decreased T3 and 4 secondary: all 3 decreased
what is primary vs secondary hypothyroidism?
primary means the issue is with the thyroid gland itself which could be due to loss of function, infiltrative disease or due to defects in hormone synthesis secondary means the issue stems from either the pituitary (TSH deficiency) or hypothalamus (TRH def)
what is the most frequent cause of primary hypothyroidism in developed countries vs worldwide?
In developed nations it is Hashimoto’s (nongoitrous), often associated with antithyroid antibodies Worldwide it is iodine deficiency (causes goiter)
what are the relative levels of TSH, T3 and 4 in hypERthyroidism?
increased T3 and T4, decreased TSH
what is the most common cause of hyperthyroidism in the U.S. (give name and simple etiology); what can be other causes?
Grave’s disease: development of circulating IgG against TSH receptors on the thyroid, causing overproduction of T3 and T4 due to the negative feedback Cam also be due to toxic multinodular goiter (Plummer’s) or adenoma on thryoid
what is another term used in place of hyperthyroidism and it smeaning
thyrotoxicosis, defines the hypermetabolic state induced by increased amounts of circulating T3 &4
what is the function of ACTH
adrenocorticotropic hormone, made in the ant pit, stimulates the adrenal cortex to secrete glucocorticoids, esp cortisol
In Addison’s disease, what will be circulating in increased amounts and why?
increased circulating ACTH bc of a lack of cortisol to act as the negative feedback stimulus
among the glycoprotein hormones of the ant pit, how are the hormones structured and what is distinctive between them?
they are of two peptide chains with carbohydrate moieties. The alpha subunits are similar, but the B subunits distinguish them from each other
what is another term for TSH and what does it promote the thyroid gland to do?
thyrotropin; promotes growth and uptake of iodine and stims secretion of the thyroid hormones
what are alternative terms for ADH, where is it formed and stored?
arginine vasopressin or just vasopressin; formed in neurons of the hypothalamus and stored in the posterior pituitary (neurohypophysis)
what does ADH/vasopressin do to: capillaries/arterioles intestinal muscles kidney tubules
- stims contraction of capillary and arteriole muscle to raise blood pressure 2. promotes contraction of GI muscles to cause peristalsis 3. causes reabsorption of free water to concentrate urine and dilute blood serum
what regulates ADH secretion, PRIMARILY? secondarily? other?
plasma osmolarity; baroreceptors that respond to changes in blood volume; many other stimuli can cause ADH release: pain, stress, sleep, exercise, chemi agents like angiotensin II, catecholamines
where is oxytocin made and stored?
hypothalamus, stored in post pit
on what part of the kidney does ADH act ?
the distal convoluted tubules to increase water reabsorption
what disorder is associated with ADH excess and lack?
excess: SIADH lack of: diabetes insipidus
what is the effect of diabetes insipidus on electrolyte levels? SIADH?
It concentrates them bc too much fluid is lost, so hypernatremia; too much fluid retained without electrolyes, so in SIADH, hyponatremia
where are human steroid hormones synthesized primarily, and from what precursor substance?
in the adrenals and gonads; from cholesterol acquired from circulating LDL or it can also be synthesized intracellularly
where are steroids metabolized and how excreted?
in the liver, and to a lesser extent in kidney and GI tract; they are conjugated with glucuronic or sulfuric acids to be excretes as water-soluble metabolites in the urine
what are three major categories of steroids synthesized in adrenals?
glucocorticoids (think cortisol), mineralocorticoids (think aldosterone) and adrenal androgens plus progesterone and estrogen (obv also made in gonads)
major actions of cortisol the primary glucocorticoid include:
affects all macronutrient metabolism including raising blood glucose and release of FFAs OR lipogenesis have antiinflammatory properties, thus are used therapeutically
Name and primary function of the most potent mineralcorticoid
aldosterone; regulates salt homeostasis and ECF
where in the adrenal are the glucocorticoids and mineralocorticoids synthesized?
cortex, specifically the zona fasciculata and glomerulosa respectively
what are the most important adrenal androgens
DHEA/ dehydroepiandrosterone and androstenedione
in a normal individual how would cortisol levels be between a morning and afternoon sample?
levels are diurnal, higher at 8 a.m. and lower at 4 p.m.
In decreased cortisol production such as in Addison’s disease, how would blood glucose be affected?
lower- more likely hypoglycemic
what regulates secretion of adrenal glucocorticoids and androgens? what regulates this regulator in turn?
ACTH from the posterior pituitary, which is in turn regulated by CRH from the hypothalamus
what is the primary control mechanism for secretion of aldosterone? what does aldosterone do?
the renin-angiotensin system; aldosterone increases Na+ reabsorption (thus water) and potassium excretion
In Hyperaldosteronism, what is the effect on sodium and potassium?
increased serum Na+ (hypernatremia) and reduced K+, hypokalemia
what part of the nephron does aldosterone exert its effect upon?
the distal tubule
what 3 main hormones are made in the adrenal cortex vs adrenal medulla?
cortex: glucocorticoids (cortisol), mineralocorticoids (aldosterone), and androgens (testosterone)
medulla: the catecholamines which includes epi, norepi, and dopamine
what is the overarching function of the catecholamines and what are the 3 main ones metabolized into?
mobilization of energy stores, esp norepinephrine, epinephrine: increase BP, blood glucose (fight or flight response); dopamine is a neurotransmitter and has key roles in locomotion, learning, reward center of brain.
norepinephrine: becomes normetanephrine—>vanillylmandelic acid (VMA)
epinephrine is metabolized to metanephrine—>VMA
dopamine—> homovanillylmandelic (HVA)
what is a pheochromocytoma? sign and sx? lab values?
a tumor of the adrenal gland chromaffin cells that produces catecholamines
s&sx: HTN, headache, palpitations, excess sweating, nausea, anxiety, weakness
lab values: incrsd plasma catecholamines; increased urinary metanephrines and VMA
what is a neuroblastoma, plus lab analytes to aid diagnosis
tumors almost all occuring in children deriving from neural crest cells, ~60% extraadrenal and ~40% adrenal. most found in abdominal areas. Metabolites HVA (of dopamine) and VMA (of norep) in urine is most used lab testing
what pituitary hormones rise at ovulation? other?
FSH and LH; also estrogen/estradiol
when does progesterone rise?
about 8 days after the LH peak, so also after ovulation
what is the principle estrogen? what happens to it at full term pregnancy?
estradiol; should increase or plateau at full term
what is the function of progesterone?
to prepare the uterus for pregnancy by maintaining the uterine lining, inhibiting contractions, and preparing breasts for lactation
When is progesterone higher than normal, from a lifetime perspective?
durig peri-menopause
what is the function of HCG?
it maintains progesterone in earrly pregnancy
