GROWTH HORMONE (GH) or Somatotropin

Question 1

 Protein Poly-peptide hormone
 Most abundant of all pituitary hormones
 It stimulates growth and cell reproduction and regeneration in humans and other animals.
 Structurally similar to prolactin and human placental lactogen
 Markedly elevated during sleep (deep sleep)
 The overall metabolic effect is to metabolize fat stores while conserving glucose

Answer 1

Growth hormone (GH)

Question 2

Growth hormone (GH) is controlled by

Answer 2

GHRH and Somatostatin

Question 3

 Growth hormone is used clinically to treat children’s growth disorders and adult growth hormone deficiency. In recent years, replacement therapies with human growth hormones (HGH) have become popular in the battle against aging and weight management.
 At this time HGH is still considered a very complex hormone and many of its functions are still
unknown.
 Reported effects include

Answer 3

decreased body fat,
increased muscle mass, increased bone density, increased energy levels, improved skin tone and texture, increased sexual function and improved immune system function.

Question 4

Specimen requirement:
Reference Interval:

Answer 4

Specimen requirement: fasting serum, complete rest for 30 minutes before collection
Reference Interval: below 1 ng/ml (<1g/L)

Question 5

Stimulators of GH secretion include:

Answer 5

 peptide hormones
 sex hormones
 clonidine and L-DOPA by stimulating GHRH release
 hypoglycaemia, arginine and propranolol by inhibiting somatostatin release
 deep sleep
 fasting
 vigorous exercise

Question 6

o Growth hormone releasing hormone (GHRH also known as somatocrinin) through binding to the growth hormone releasing hormone receptor (GHRHR)

Answer 6

peptide hormones

Question 7

o increased androgen secretion during puberty (in males from testis and in females from adrenal cortex)
o estrogen

Answer 7

sex hormones

Question 8

Inhibitors of GH secretion include:

Answer 8

 somatostatin from the periventricular nucleus
 hyperglycemia
 glucocorticoids

Question 9

Growth hormone has many other effects on the body:

Answer 9

 Increases calcium retention, and strengthens and increases the mineralization of bone
 Increases muscle mass through sarcomere hyperplasia
 Promotes lipolysis
 Increases protein synthesis
 Stimulates the growth of all internal organs excluding the brain
 Plays a role in fuel homeostasis
 Reduces liver uptake of glucose
 Promotes gluconeogenesis in the liver
 Contributes to the maintenance and function of pancreatic islets
 Stimulates the immune system

Question 10

Excesses

Answer 10

 Prolonged GH excess thickens the bones of the jaw, fingers and toes. Resulting heaviness of the jaw
and increased thickness of digits is referred to as acromegaly (>50 ng/ml). Accompanying problems can include pressure on nerves, muscle weakness, insulin resistance or even a rare form of type 2 diabetes, and reduced sexual function.
 The excessive GH can cause excessive growth, traditionally referred to as pituitary gigantism.
 Exercise and fasting (burst of GH secretion occur)
 Liver disease
 Renal disease
 Anorexia nervosa