Physiology - Growth Hormone and Acromegaly Flashcards
What kind of molecules are GHRH and GH?
Peptides
What is the ubiquitous role of somatostatin?
It inhibits cellular proliferation and activity
Describe the GH peptide.
191 AAs with 2 disulfide bonds
What hormone has a similar structure to GH? What is the small difference?
PRL3 disulfide bridges instead of 2`
How is the similar structure of PRL and GH put to use in real life?
Bovine GH can bind both GH and PRL receptors so it’s administered to cows to increase their size and milk production
Draw the feedback loops involved with GH production by pit.
INSERT IMAGE HERE
What is the major organ destination for GH?
The liver
What hormone does the liver produce upon receiving GH? 2 names
Somatomedin C = Insulin-Like Growth Factor-1 (IGF-1)
What kind of feedback is triggered by IGF-1 production by the liver?
3 long feedback loops:- GH to ant pit+ SS to hypo-GHRH to hypo
How does GH production by ant pit affect hypo?
Short loop:+ SS- GHRH
What are the main 3 cellular processes stimulated by GH?
- Growth2. Cell reproduction3. Cell regeneration
Is GH a metabolic or anabolic hormone?
Anabolic
4 effects of IGF-1 on visceral tissue and organs (bones, heart, lungs, kidneys, pancreas, intestines, skin, connective tissues)? Overall effect?
- protein synthesis2. + RNA synthesis3. + DNA synthesis4. + cell size/function= Increase size/function
7 effects of IGF-1 on chondrocytes? Overall effect?
- AA uptake2. + protein synthesis3. + RNA synthesis4. + DNA synthesis5. + collagen6. + chondroitin sulfate7. + cell size/number= LINEAR GROWTH when growth plates are open
What are chondrocytes?
Bone cells
3 effects of GH on adipose tissue? Overall effect?
+ lipolysis- glucose uptake+ glycolysis = DECREASED ADIPOSITY
4 effects of GH on liver tissue?
- RNA synthesis2. + protein synthesis3. + gluconeogenesis4. + IGF-1
3 effects of GH on nonactive muscles? Overall effect?
- glucose uptake2. + AA uptake3. + protein synthesis= LEAN BODY MASS
How do GNRH and SS affect each other?
They both inhibit each other’s production
What are the 8 factors that stimulate GH secretion?
- Glucose decrease2. FA decrease3. AA increase (especially Arg)4. Fasting5. Stage 4 sleep (1 hour after sleep onset)6. Exercise7. Actute stress8. Sex hormones 9. Alpha-adrenergic agonists
What are the 8 factors that inhibit GH secretion?
- Glucose increase2. FA increase3. Cortisol = chronic stress4. Obesity5. Pregnancy6. SS7. GH 8. IGF-1
Why is GH said to be a hyperglycemic hormone?
Because it raises glucose levels through gluconeogenesis and decrease glucose uptake by adipose tissue and muscle
Why is GH inhibited by pregnancy?
Because placenta makes its own called HPL which has a short loop negative feedback on hypo: + SS and - GHRH
How often does GH secretion happen during a normal 24h day?
Every 4 hours
How does GH production vary during the life span? What hormones is this similar too?
GH is low at birth, increases during childhood, peaks at puberty, and continues to decrease during adult life and senescenceSAME AS SEX HORMONES
What is acromegaly due to? To what patients?What are the symptoms?
Pit tumor (micro or macro) causing overproduction of GH in adults (middle age)Symptoms: overgrowth of soft tissues of face (nose and lips), hands, feet, and bones
What is gigantism due to? What are the symptoms?
Macroadenoma causing overproduction of GH in children (before closure of epiphysial endplate in puberty)Symptoms: incredible height (7-8 feet), and sometimes acromegaly in adulthood
What is pituitary dwarfism due to? What are the symptoms?
Inability of pit to produce enough GHSymptom: insufficient stature growth
What is Laron dwarfism due to? What are the symptoms?
Special subset of pit dwarfism due to lack of functioning GH receptors Symptoms: insufficient stature growth and high GH because IGF-1 is not produced
What is wide-range hypopituitarism?
When a patient has a dysfunction of many cell types contained in the anterior pit
How does low LH affect testosterone levels? What does this cause?
Low testosterone levels causing decrease in libido and body hair AND decrease in hematocrit
Why would administering fluids to a patient with macroadenoma worsen his condition?
Because the added fluid in the sella turcica will increase pressure
What are the post-op treatments of hypophysectomy of macroadenoma?
End-organ hormone replacement therapy
Why could macroadenoma cause increase in PRL?
If tumor is really pressing hard it is cutting flow of venous blood from the hypo to pit gland so dopamine is not making it to the pit
Are pit tumors usually cancerous/metastatic?
NOPE
Which predominates on GH production: GHRH or SS?
GHRH: net increase
When can GH bind to PRL receptors?
When GH is in excess
How does testosterone affect GH production? Why?
It substantially increases GHRH and SS so it causes episodic levels of GH (high peaks and very low baseline level)Causes maximal somatic growth
How does estrogen affect GH production?
It moderatly increases GHRH and SS so it causes disorganized episodic levels of GH (lower peaks and higher baseline level than in males)
How would a treatment of peptide hormones need to be administered?
Via IV
