Anterior Pit - GH/Prolactin

how is growth hormone transported

via growth hormone binding proteins

Somatrotrophs vs Lactotrophs

somatotrophs - GH

Lactotrophs- Prolactin

Where is GH synthesized + secreted from

anterior pit

How is GH released + when is most of it released

pulsatile bursts

Slow Wave Sleep

What stimulates GH release

GH-RH: Hypothalamus releases (growth horm releasing horm) via Gs

Ghrelin (incr appetite) = incr GH

exercise, estrogen/testosterone, catecholamines, dopamine, hypoglycemia (low glucose)

what inhibits GH release

• Somatostatin

  • directly (acts on somatrophs)

  • Indirectly via inhibiting GH-RH + inhibiting grehlin

• GH inhibits GR-RH (via short/more direct route )

• IGF = inhibit GH-RH (via long route that involves liver)

• KNOW: GLUCOSE, FFA, PROGESTERON

GH receptor is part of what family + what is required for activation

cytokine family

dimerization + phosphorylation

What pathway does GH act in:

JAK2-STAT

Describe GH vs IGF-1 (sim + differences)

Both: Incr bone growth + Incr protein synthesis

Differ:

GH: anti-insulin activity, INCR lipolysis

IGF-1: insulin like (“insulin like growth factor” ), DECR lipolysis

EXCESS GH = leads to… what conditions

acromegaly + giganticism

• enlarged hands/ feet, osteoarthritis, soft tissue swelling, weight gain, escessive sweating, hypertension, big organs, INSULIN RESISTANCE (hyperglycemia + hyperinsulinemia), VISUAL ISSUES - bitemporal hemianopia (loss of peripheral vision in both eyes)

Most important stimulator of bone growth:

GH-RH - GH - IGF-1 Axis

What type of receptor does prolactin use + what signaling pathway

same as GH: cytokine family

dimerization + phosphorylation required

JAK2-STAT

How is prolactin inhibited (primarily)

Via dopamine (D2R - Gi) -Gi (inhibitory)

*note prolactin itself = increases dopamine

What stimulates prolactin:

SUCKING: removes inhibition from dopamine

Estrogen (think after birth = estrogen is high + baby needs to suck), TRH, AVP/OXT (the posterior pit hormones), serotonin, sleep

Signs of EXCESS PROLACTIN

• galactorrhea - milky discharge from breast

• Amenorrhea (no periods) + infertility

• Decr libido or erectile dysfunction in men

• Visual disturbances (due to tumor on ant pit) - bitemporal hemianopia (no peripheral vision)

What type of thyroid disturbance is associated with EXCESS PROLACTIN

primary HYPO thyroidism = can cause EXCESS prolactin

• TRH = stimulates prolactin

• When T3/T4 are low = stimulates an increase in TRH = indirectly causes incr prolactin

What is the effect of cutting the pituitary stalk on prolactin levels

they will INCREASE!

removes dopamine inhibitory effect on prolactin