Intro to endocrinology and pituitary

Question 1

Classes of hormones

Answer 1

Glycoproteins: FSH, TSH, LH, hCG
Polypeptides: ACTH etc
Steroids: Aldosterone, Cortisol, Estradiol, Progesterone, , Testosterone, Vitamin D
Amines: Epinephrine, Norepinephrine, T3, T4

Question 2

Plasma half life and MCR

Answer 2

Thyroid hormones are VERY tightly bound so the half life is really long and the MCR is slow

Steroids: CORT and Testosterone are tightly bound so the half life is really long and the MCR is slow/low

but Aldosterone is not bound much so half life is short and MCR is high/fastest

Peptide hormones are not bound at all so the half life is almost zero, and the MCR is super fast

ITS THE FREE BIOLOGICALLY ACTIVE FORM thats of note

Question 3

Endocrine rhythms

Answer 3

1. Circadian (revolves around the 24 hr day)
2. Ultradian (frequent bursts)
3. Stimulus induced
4. seasonal

Question 4

Glucose, insulin, glucagon loop

Answer 4

if glucose is low, it stimulates alpha cells to produce glucagon which stimulates the liver to make glucose (gluconeogenisis)

When glucose is high, it stimulates Beta cells to produce insulin which tells the liver to stop wasting energy making glucose and tells the body to uptake glucose

This liver pancreas situation is called a parallel negative feedback loop

Question 5

Mechanism of action of g-protein coupled receptor

Answer 5

Hormone activates receptor, inactive (alpha, beta, gamma subunits) g-protein complex associates with the receptor and is activated. GTP->GDP, which causes the alpha subunit to dissociate from beta and gamma to interact with membrane bound target proteins that initiate intracellular signals

The active membrane protein ATP->cAMP, the cAMP activates cAMP dependent protein kinases which activates a protein

Question 6

G-protein coupled to PLC IP3 and DAG second messenger

Answer 6

Peptide hormones bind and activate to receptor which activates a G protein which activates Phospolipase C.

phospholipase C (PLC) converts (PIP2) to (DAG and IP3)

Leads to activation of protein kinase c, dephosphorylates a protein -> cells response

Also leads to calcium release-> cell response

Question 7

Intracellular (cytoplasmic and nuclear) receptors

Answer 7

CORT is a good example

Hormone (steroids) diffuses right into cell, activates the cytoplasm receptor or the nucleus receptor,

The hormone/receptor complex attaches to the hormone response elements which activates transcription, translation and proteins that cause a change.

even if the receptor is in the cytoplasm it will still go into the nucleus

ALL ARE NUCLEAR RECEPTOR family

Question 8

Mechanism of action of thyroid hormones via nuclear receptor

Answer 8

Some hormones are altered in target tissue Thyroxine (T4) is secreted from the thyroid gland but does not bind well to the binding receptor so its altered to T3 in cytosol to regulate amount of active thyroid hormone

Question 9

pituitary anatomy

Answer 9

neurons with cell bodies in hypothalamus release hormones that activate or inhibit the release of hormones in the pituitary median eminence that go to two places, artery (that reach the whole body) and the portal vessels that lead to the anterior pituitary

Question 10

Classes of anterior pituitary hormones

Answer 10

Glycoproteins: TSH (stimulates thyroid hormone release from thyroid gland), LH (ovaries and testes), FSH (ovaries and testes), hCG

Growth hormone and prolactin family (amino acid homology)

POMC: a gene produces a polypeptide thats post translationally modified to ACTH and melanin

Question 11

Hypophysiotropic hormones

Answer 11

CRH (corticotropin releasing hormone)-stimulates ACTH
GnRH (gonadotropin releasing hormone)-stim. FSH and LH
GHRH (growth hormone rel. hor.) -stim GH
SRIF- inhibits GH
Prolactin stim factor
Prolactin inhib factor aka DOPAMINE
TRH- thyrotropin releasing hormone- stim TSH and prolactin