growth hormone Flashcards
What is the pattern of release of GH?
Pulsatile release, increased release at night.
In which stage of life are GH levels the greatest?
puberty
What are the functions of GH?
Promotes growth of bone and muscle, and increases blood glucose levels
How does GH stimulate bone and muscle growth?
GH stimulates the release of IGF-1 (insulin-like growth factor), which stimulates mitosis in bone and muscle
What are the metabolic effects of GH?
Restricts cellular uptake of glucose to raise blood glucose. Stimulates lipolysis in adipose tissue to supply fatty acids for energy. Increases gluconeogenesis in the liver. Stimulates protein synthesis in muscle
What are the negative feedback loops for GH?
GH and IGF-1 provide negative feedback to the hypothalamus
What hormone inhibits release of GH?
Growth Hormone Inhibiting Hormone (GHIH), AKA somatostatin
What condition is caused by excess secretion of GH in childhood?
Gigantism
What are the causes of gigantism?
pituitary adenoma, genetic mutations
What are the symptoms of gigantism?
Abnormally rapid childhood growth of height/size. Enlarged hands, feet, facial features. Joint pain
What investigations may diagnose gigantism?
Bloods may show elevated GH or IGF-1,
Oral glucose tolerance test may fail to supress GH levels indicating adenoma.
MRI/CT may show adenoma
What are the non-pharmalogical treatments for gigantism?
surgical/radiation tumor removal
What are the pharmalogical treatments for gigantism?
Somatostatin analogue (potent inhibitor of growth hormone release)
What condition is caused by excess GH in adults?
Acromegaly
What are the causes of acromegaly?
Pituitary adenoma, ectopic GH or GHRH producing tumor
What are the symptoms of acromegaly?
enlarged hands, feet, jaw, nose, brow. Thickened skin, deepened voice, increased tooth spacing, glucose intolerance
What investigations are used to diagnose acromegaly?
Bloods may show elevated GH/IGF-1, oral glucose tolerance test not supressed suggests adenoma, MRI/CT may show adenoma
What are the non-pharmalogical treatments for acromegaly?
Surgery/radiation removal of adenoma
What are the pharmacological treatments for acromegaly?
somatostatin analogues
What condition is caused by a lack of growth hormone?
Pituitary dwarfism/growth hormone deficiency
What are the causes of GH deficiency?
Congenital pituitary abnormalities, pituitary damage from trauma/tumours/radiation/infection
What are the symptoms of GH deficiency?
slow growth rate, short stature, reduced muscle mass, delayed puberty, high lipids
What are the investigations used to diagnose GH deficiency?
GH stimulation test will show no response to insulin, Bloods will show low GH/IGF-1, xrays will show delayed bone age
What is the pharmacological intervention for GH deficiency?
Somatotrophin (growth hormone analogue) injections
What is a glucose supression test?
Glucose is given to a patient and GH levels are tested to see if they are inhibited normally. If suppression does not occur then there is likely a GH secreting tumor
