Page 118 - Clinical Biochemistry 08PB804

 High levels are also seen with:
1- Anorexia nervosa
2- Drugs:
• Tricyclic antidepressants, that block the effect of dopamine (a brain chemical that regulates
and inhibits the production of prolactin) such as: tranquilizers and some hypertension drugs
 Low levels are also seen with:
1-Hypopituitarism (decreased pituitary function and decreased hormone production).
2-Low levels may also be caused by drugs such as: Dopamine, Levodopa, Ergot alkaloid
derivatives.
5-Growth Hormone (GH)
• Human growth hormone (also called somatotropin) is a protein of 191 amino acids.
• The GH-secreting cells are stimulated to synthesize and release GH by the intermittent arrival
of growth hormone releasing hormone (GHRH) from the hypothalamus.
• GH promotes body growth by:
- Binding to receptors on the surface of liver cells & this stimulates them to release insulin-like
growth factor-1 (IGF-1; also known as somatomedin)
- IGF-1 acts directly on the ends of the long bones promoting their growth
In childhood:
1-Hyposecretion of GH produces Dwarfism
Growth retardation can also result from an inability to respond to GH.
2-Hypersecretion leads to Gigantism
In adults:
Hypersecretion of GH or GHRH leads to Acromegaly.
Dwarfism
Results from hypo secretion of the growth hormone of the pituitary gland, which has been
caused by a tumor, infection, genetic factors, or trauma.
Gigantism
An excessive growth of the long bones caused by hyper secretion of the somatotropic hormone
(pituitary gland).