Growth hormone disorders

Question 1

What is secreted by the posterior pituitary?

Answer 1

Oxytocin and ADH

Question 2

What is secreted by the anterior pituitary?

Answer 2

TSH, ACTH (adrenocorticotrophic hormone), GH, FSH, LH, prolactin and many more

Question 3

How is the pituitary gland linked to the hypothalamus?

Answer 3

By the pituitary stalk, which is composed of blood capillaries and nerve fibres

Question 4

Describe the anatomy of the pituitary gland

Answer 4

rich in blood vessels, nervous tissue, surrounded by a bony cavity, found at the base of the skull, 75% composed of anterior pituitary (adenohypophysis), 25% composed of the posterior pituitary (neurohypophysis)

Question 5

What are the functions of GH?

Answer 5

Increases cellular uptake of amino acids, increases synthesis of proteins, increases glucose concentration in the blood, increases fat metabolism and promotes epiphyseal bone growth

Question 6

How much of GH is bound? and to what?

Answer 6

70% is bound to growth hormone binding hormone

Question 7

GH doesn’t act directly on cells, most of its effects are mediated by something else, give an example

Answer 7

The liver, more specifically IGF-1 and IGF-2, which are polypeptides and act locally to promote cellular proliferation and differentiation

Question 8

What affects the regulation fo GH?

Answer 8

GHRH - which is affected by sleep, exercise, amino acids and stress
Somatostatin - made in hypothalamus, inhibits the release of GH from the anterior pituitary, somatostatin can be influenced by high blood sugar levels

Question 9

What are the 3 stages of growth during one’s life?

Answer 9

• Rapid growth during the first 2 years of life, largely due to nutrition, not GH
• Steady growth for approx 9 years controlled by GH
• rapid growth during puberty controlled by both GH and sex hormones

Question 10

What other hormones are involved in growth?

Answer 10

Thyroxine, TH, cortisol, insulin

Question 11

What is achondroplasia?

Answer 11

An inherited short stature disorder causing defective bone cartilage

Question 12

How would you test for GH deficiency?

Answer 12

• Stimulate GH release, if failure indicates deficiency or disease
• Get individual to undergo hard physical exercise and take 3 blood samples at 0, 2 and 20 minutes

Question 13

What are signs of GH deficiency in an adult?

Answer 13

impaired hair growth, proneness to hypoglycaemia, poor muscular tone, osteoporosis (bones fracturing easily)