Endocrinology Exam 2

GH target organs

liver, bone, muscle

PRL

?

somatotroph

secrete growth hormone

Growth Hormone Cascade

1. Hypothalamus releases Growth Hormone releasing hormone (GHRH)

2. stimulates anterior pituitary to release growth hormone

3. GH goes to all tissues

4. Liver releases insulin like growth factor 1

Galen

thought pituitary drains phlegm

Pierre Marie

1886 - named the disease acromegaly [from greek words of akron aka tip or extremity]

Minkowski

1887 - linked acromegaly with pituitary tumor

Aschner

1909 - found that hypophysectomy causes dwarfism

Evans and Long

1921 - showed that anterior lobe extract increases growth rate in rats

Li and Evans

1945 - isolated GH from anterior pituitary

Knobil and Greep

1955 - show the GH has species specificity

Raben

1957 - pituitary extracts from cadavers used to treat GH deficienct

Yallow

1963 - radioimmunoassay for GH

Li

1971 - synthesis and structure of hGH

Genentech did what?

1979 - hGH cloned

1985 - recombinant hGH approved for use in children for growth deficiency

Monsanto

1994 - rbGH approved for use in dairy cattle for increasing milk production (limited use to increase growth in swine)

Release schedule of GH

Released in pulses usually at night. Levels start to decline after age 14

Dwarfism

either laron (receptor mutation) or pituitary (no release of GH, treatable)

GHRH

hypothalamic releasing factor that increases GH release

Somatostatin

Hypothalamic releasing factor that decreases GH release

Anterior pituitary hormone releasing mechanism

releasing factors from hypothalamus go through the median eminence to stimulate the release of AP hormones

GH feedback loops

Ultra short loops: somatostatin, GHRH and Gh are their own negative feedback loops

Short loop: GH activates somatostatin and deactivates GHRH

Long: IGF-1 turns off GH and GHRH