Growth Hormone & Gonadotropins

Question 1

1. How is GH transported?
2. What is GH’s overall effect?

Answer 1

1. Transported BOUND TO GH-BINDING PROTEIN
2. Use up fat stores & promote protein synth.

Question 2

What are Insulin-like growth factoes (IGFs) (somatomedins)?

Answer 2

Peptide hormones w. strong mitogenuc properties (encourage cell division)

Produced I^o in liver, but also in most other tissues (where it has an auto-/paracrine effect).

THERE ARE 2 TYPES!

Question 3

What are the 2 types of IGFs?

Answer 3

IGF-1

effects most cells in body where it stimulates cell growth multiplication & inhibits apoptosis

IGF-2

a growth-promoting hormone during gestation

Question 4

What effects does GH have on GROWTH?

Answer 4

–Hyperplasia (increase # cells)

–Hypertrophy (increase cell size)

– Increase protein synth. (decreases blood a.a’s)

– Decrease protein degradation

– Increase bone growth

Question 5

What effects does GH have on METABOLISM?

Answer 5

– Increase fat breakdown (lipolysis) (increase blood free fatty acids)

– Increase glucose output from liver (hepatic gluconeogenesis)

– Decrease insulin sensitivity in muscle

(THUS, decrease glucose uptake by muscles)

–> muscles use free fatty acids (increase blood glucose)

Question 6

How does GH regulate bone growth?

Answer 6

GH (via IGF-1 stimulating chondrocytes & osteoblasts) regulates both THICKNESS and LENGTH of bone growth.

Question 7

What happens when there is excess GH?

Answer 7

–if in childhood, body remains in proportion (GIGANTISM)

–if after adolescence, bones can’t legthen (ACROMEGALY)

Question 8

What happens when there is GH deficiency?

Answer 8

–Abnormal GH R’s = LARON DWARFISM

–IGF-1 (or R) deficiency = AFRICAN PYGMIES

Question 9

What other responses (other than growth) may occur in response to GH?

Answer 9

• Androgens areninvolved in the pubertal growth spurt and simulate protein synth. (permissive interaction with GH)
• Children with hypothyroid conditions have their growth

severely stunted, however, hypersecreUon of TH does not stimulate excess growth.

• Excess insulin stimulates excessive growth and a deficiency may block growth

Question 10

What are gonadotropins?

Answer 10

LH & FSH produced by gonadotropes in ant. pituitary!

–> acts on gonads by activating cAMP

–> some circadian rhythm

–> puberty is initiated by an increase in GnRH activity

Question 11

What do FSH and LH do in FEMALES?

Answer 11

FSH = promotes follicle growth & development

(including the induction of LH R’s on the dominant follicle)

Also stim.’s estrogen secretion from follicles

LH = maintains development of corpus leuteum & estrogen/progesterone secretion

Question 12

What do FSH and LH do in MALES?

Answer 12

FSH = stim. sperm production

LH = stim. testosterone

Question 13

Answer 13