Hypothalamus And Pituitary - Block (Bill)

Question 0

Compare the structures of Vasopressin and Oxytocin

Answer 0

Both are nonapeptides with intramolecular disulfide bonds. Primary structures only differ by 2 amino acids.

Question 1

Where are the following hormones synthesized, secreted, and what is the function of each?
Vasopressin
Oxytocin
Growth Hormone
Prolactin

Answer 1

Vasopressin- synthesized in hypothalamus, inhibits water diuresis, secreted in posterior pituitary.

Oxytocin- synthesized in hypothalamus, stimulates uterine contraction, parturition, lactation, secreted in posterior pituitary .

Growth hormone- synthesized/secreted in Anterior Pituitary. Affects metabolism in all parts of the body. Increases protein synthesis, amino acid transport into muscles, gluconeogenesis……it decreases glucose utilization (counter regulatory hormone), and is mediated by somatomedin and IGF-1 in liver.

Prolactin- synthesized/secreted Anterior Pituitary, stimulates lactation and protein synthesis.

Question 2

What is the situation with respect to growth hormone and it’s receptors in Laron dwarfs, GH deficient dwarfs, pygmies, acromegaly, and gigantism?

Answer 2

GH Deficient dwarfs- not enough GH, infant does not grow properly.

Laron type dwarfs- Too much growth hormone, but lack hepatic receptors, causing low levels of IGF (insulin like growth factor)

Pygmies- A post GH receptor defect. Normal levels of GH, low levels of IGF.

Acromegaly- Excessive GH secretion after epiphyseal closures protruding jaw, large nose, feet, hands, skull.

Gigantism- Excessive GH secretion before epiphyseal plates close. Usually caused by an acidophilic tumor, accelerated growth in the long bones.

Question 3

Name 3 glycoprotein hormones synthesized and secreted in the anterior pituitary and give their functions.

Answer 3

1. TSH- Increases the volume and vascularity of the thyroid gland, iodide concentration, stimulates synthesis and release of thyroid hormones, increases lipolysis of adipose.
2. FSH- stimulates growth/development of ovarian follicle, increases spermatogenesis in men.
3. LH- Causes ovarian follicle to mature, induces ovulation, stimulates androgen production by Leytig cells.

Question 4

What is the POMC family of hormones? Give three members, their function, and where they are synthesized/secreted.

Answer 4

POMC are a family of peptides that act as hormones, neuromodulators, and neurotransmitters. Gives rise to alpha MSH and CLIP. Processing takes place in the gut and reproductive tract.

ACTH- regulates growth/fxn of adrenal cortex. At the n terminus containing amino acids 1-39.

Beta LPH- amino acids 42-134 of POMC . Causes lipolysis and fatty acid mobilization.

Gamma MSH- melanocyte stimulating hormone. Causes dispersion of intracellular melanin granules ( skin darkening).

Question 5

What is Cushing’s Syndrome?

Answer 5

Cushing’s is excessive ACTH production by the pituitary or a tumor.

This causes hyper pigmentation from production of MSH, which leads to muscle atrophy and redistribution of fat due to sodium retention, glucose intolerance, increased plasma fatty acids, decreased eosinophils and lymphocytes, increased polymorphonuclear leukocytes, and negative nitrogen/potassium/phosphorus balances

Question 6

What are endorphins? Where are they synthesized and secreted?

Answer 6

Endorphins are synthesized/secreted in the Anterior Pituitary. They bind to morphine receptors and play a role in pain reception.

Question 7

Give 4 releasing hormones and 2 inhibitory factors secreted by the hypothalamus list their functions.

Answer 7

Releasing

1. TRH- stimulates release of thyrotropin and prolactin.
2. GnRH- Stimulates release of luteinizing hormone and follicle stimulating hormone.
3. CRG- Stimulates release of ACTH+ beta endorphin
4. GHRH- Growth hormone releasing factor

Inhibitory

1. GHR- (Somatostatin) Inhibits growth hormone, insulin, glucagon, gastrin
2. PRL- Inhibits Prolactin release.