Hormones

Question 1

Growth Hormone (somatotropin)

Answer 1

• secreted by anterior pituitary
• Stimulates linear growth and muslce mass through IGF-1 (somatomedin C) secretion. Increases insulin resistance (diabetogenic)
• Released in pulses in response to GHRH. Secretion inc during sleep/exercise, inhibited by glucose and somatostatin release via negative feedback by somatomedin.
• Excess secretion of growth hormone (pituitary adenoma) may cause acromegaly (adults) or gigantism (children)

Question 2

Ghrelin

Answer 2

Stimulates hunger and GH release. Produced by stomach. Increased with sleep loss and Prader-willi syndrome

Question 3

Leptin

Answer 3

Satiety hormone (think Lep-thin). Produced by adipose tissue. Decreased during starvation. Mutation of leptin gene –> congenital obesity. Sleep deprivation –> decrease leptin production.

Question 4

Endocannabinoids

Answer 4

Stimulate cortical reward centers –> inc desire for high fat foods (the munchies)

Question 5

ADH

Answer 5

• Synthesized in hypothalamus (supraoptic nuclei), released by posterior pituitary.
• Regulates serum osmolarity (V2 receptors) and blood pressure (V1 receptors). Primary function is serum osmolarity regulation (ADH dec serum osmolarity, increase urine osmolarity) via regulation of aquaporin channel insertion in principal cells of renal collecting duct.
• Release regulated by osmoreceptors in hypothalamus (primary) and hypovolemia (secondary)
• Levels are dec in central DI (can tx w/Desmopressin), inc in nephrogenic DI (nephrogenic can be caused by mutation in V2) receptor)

Question 6

Prolactin

Answer 6

• Secreted mainly by anterior pituitary, tonically inhibited by DA, TRH increases secretion
• Stimulates milk production in breast, inhibits ovulation in females and spermatogenesis in males by inhibiting GnRH synthesis (excessive amts associated with dec libido)
• Prolactin will inhibit its own secretion by increasing DA release from the hypothalamus
• DA agonists used to tx prolactinoma, Antagonists and estrogens stimulate secretion.

Question 7

Cortisol

Answer 7

• Synthesized in zona fasciculata
• Increases BP (upregulates a1 on arterioles and @ high conc binds mineralocorticoid receptors)
• Inc insulin resistance
• Inc Gluconeogenesis/lipolysis/proteolysis
• Dec fibroblast activity (causes striae)
• Dec inflammatory and immune responses
• Dec bone formation (dec osteoblast activity)

Question 8

Vitamin D

Answer 8

• D3 from sun, D2 from plants. Both converted to 25-OH in liver, 1,25(OH)2 in kidney.
• inc dietary absorption of Ca and PO4
• inc bone resorption –> inc Ca and PO4
• inc PTH, Dec Ca/PO4 –> inc 1,25(OH)2 production.

Question 9

Parathyroid Hormone

Answer 9

• Source: chief cells of parathyroid
• inc bone resorption of Ca and PO4
• inc kidney reabsorption of Ca in distal convoluted tubule
• dec reabsorption of PO4 in PCT
• inc 1,25(OH)2 D3 production by stimulating kidney 1a-hydroxylase in PCT