From what embryonic tissue is the posterior pituitary derived?
What are the three layers of the adrenal cortex? What do they secrete?
1. zona glomerulosa
2. zona fasiculata
3. zona reticulata
1. mineralocorticoids (aldosterone)
2. glucocorticoids (cortisol)
3. sex hormones (androgen)
What is the primary regulatory control of the (three layers of) the adrenal cortex?
1. zona glomerulosa - renin, angiotensin
2. zona fasiculata - ACTH, CRH
3. zona reticulata - ACTH, CRH
What cells compose the adrenal medulla? From what embryonic structure/cells do these arise?
They arise from the neural crest
What is the drainage of the left and right adrenal glands?
left: left adrenal vein --> left renal vein --> IVC
right: right adrenal vein --> IVC
From what embryonic tissue is the anterior pituitary derived?
From the oral ectoderm (Rathke pouch)
From what embryonic tissue is the adrenal cortex derived?
What hormones are secreted by the anterior pituitary?
What cells make up the endocrine pancreas? What do they secrete?
alpha cells - glucagon
beta cells - insulin
delta cells - somatostatin
What is the overall architecture of the cells of the endocrine pancreas?
The beta cells are on the inside, the alpha cells are on the outside, and the delta cells are interspersed among the beta cells.
What hormones are secreted by the hypothalamus?
What is the function of CRH?
Corticotropin Releasing Hormone stimulates the anterior pituitary to secrete:
What is the function of dopamine that is secreted by the hypothalamus?
It inhibits the secretion of prolactin by the anterior pituitary
What is the function of GnRH?
Gonadotropin Releasing Hormone functions to stimulate secretion of FSH and LH from the anterior pituitary.
What is the function of somatostatin secreted by the hypothalamus?
Inhibits secretion of GH and TSH by the anterior pituitary
What is the function of TRH?
Stimulates secretion of TSH and prolactin by the anterior pituitary.
What is the function of prolactin?
1. stimulates milk production
2. inhibits ovulation in females and spermatogenesis in males by inhibiting GnRH release
3. excessive amounts of prolactin are assoicated with decreased libido
What stimulates prolactin secretion?
3. dopamine antagonists
What inhibits prolactin secretion?
2. dopamine agonists (e.g., bromocriptine)
**Dopamine agonists are the first-line treatment for a prolactinoma
What is the function of Growth Hormone (GH)?
GH stimulates linear growth and muscle mass via stimulating the liver to produce IGF-1
Describe the regulation of GH?
GH is released is pulses in response to GHRH.
Secretion increases during sleep and exercise.
Secretion is inhibited by glucose and somatostatin.
How is ADH secretion regulated?
ADH secretion is increased in response to increased serum osmolality and decreased blood volume.
primary regulation: osmoreceptors in the hypothalamus
secondary regualtion: hypovolemia.
Relative to normal, what are the ADH levels in central diabetes insipidus?
Relative to normal, what are the ADH levels in nephrogenic diabetes insipidus?
normal or elevated
What is the treatment for central diabetes insipidus?
Desmopressin (an ADH analog)
What is the source of cortisol?
The zona fasiculata of the adrenal cortex
Describe the regulation of cortisol?
CRH (from the hypothalamus) stimulates ACTH release (from the anterior pituitary), which stimulates cortisol production in the adrenal zona fasiculata.
Excess cortisol feedback inhibits CRH, which decreases ACTH, and thus decreases cortisol production and secretion.
**Chronic stress induces prolonged cortisol secretion.
Briefly, what are the effects/functions of cortisol?
1. increases BP
2. increases insulin resistance
3. increases gluconeogenesis, lipolysis, and proteolysis
4. decreases fibroblast activity
5. decreases inflammatory and immune response
6. decreases bone formation
What does cortisol increase blood pressure?
Cortisol increases the expression of alpha-1 adrenergic receptors on arterioles --> increases blood vessel sensitivity to norepinephrine and epinephrine --> increased blood pressure.
**Cortisol is essential for life, and is required to maintain vascular tone. A lack of cortisol can lead to fatal hypotension.
How does cortisol decrease the inflammatory and immune response?
1. inhibits phospholipase A2, and therefore inhibits prostaglandin and leukotriene production
2. inhibits leukocyte adhesion --> neutrophilia
3. blocks histamine release from mast cells
4. Blocks the production of IL-2
5. decreases the number of eosinophils
Why are abdominal straie observed in a high cortisol state?
Cortisol decreases fibroblast activity, which impairs collagen formation. This causes blood vessels to become weaker and more prone to rupture. The straie are due to ruptured blood vessels.
Why does cortisol decrease bone formation?
Because cortisol decreases osteoblast activity.
Why is cortisol diabetogenic?
cortisol increases insulin resistance