Growth hormone

Question 1

What is the main action of Somatotropin?

Answer 1

1.** Anti insulin like effects;**
* Increase blood glucose levels by increasing gluconeogenesis and glycogenolysis from the liver
* Stimulate lipolysis of adipose tissue - increase fatty acids in the blood

1. Stimulates cell growth, division and differentiation
   * Stimulates protein synthesis
   * Increases lineal growth - stimulates bone osteoblast activity

Question 2

What is the MOA of somatotropin release?

Answer 2

1. Hypothalamus - Growth hormone releasing hormone
2. Anterior pituitary gland - Somatotropin released into the bloodstream
3. High level of growth hormone/somatotropin - inhibit release of GHRH from hypothalamus

• Dopamine in the posterior pituitary gland inhibits the release of growth hormone by reducing the stimulatory effects of GHRH.

Question 3

What is the defintion of Acromegaly?

Answer 3

disorder caused by excessive secretion of growth hormone (GH) from the pituitary gland adenoma

Question 4

Clinical features : facial appearance? (5)

Answer 4

• Coarse facial appearance
• spade-like hands, increase in shoe size
• large tongue
• interdental spaces
• excessive sweating and oily skin: caused by sweat gland hypertrophy

Question 5

What are the features of pituitary tumors? (3)

Answer 5

hypopituitarism, headaches, bitemporal hemianopia

raised prolactin in 1/3 of cases → galactorrhoea

Question 6

What is the first line investigation for Acromegaly?

Answer 6

Serum IGF-1 levels - released by liver inresponse to growth hormone and promotes growth of bone and tissue

Question 7

What is the second line investigations?

Answer 7

1. OGTT test is recommended to confirm the diagnosis if IGF-1 levels are raised.
   * In normal patients GH is suppressed to < 2 mu/L with hyperglycaemia
   * In acromegaly there is no suppression of GH

Question 7

What is the process of monitoring acromegaly?

Answer 7

Serum IGF-1 may also be used to monitor disease

Question 7

What is the investigation for a suspected pituitary tumor?

Answer 7

A pituitary MRI may demonstrate a pituitary tumour

Question 8

What is the first line treatment of acromegaly?

Answer 8

Trans-sphenoidal surgery

Question 8

What is the medical management of acromegaly?

Answer 8

1. Somatostatin analogue - directly inhibits the release of growth hormone
   * Octreotide
2. Dopamine agonist
   * Bromocriptine
3. Growth hormone antagnoist
   * Pegvisomant
   * Deccreases IGF-1 levels in 90% of patients but does not reduce size so surgery may still be needed

Question 9

What are the complications of Acromegaly?

Answer 9

• hypertension
• diabetes (>10%)
• cardiomyopathy
• colorectal cancer

Question 10

Why does acromegaly cause galactorrhea?

Answer 10

1. Pituitary adenoma compresses posterior pituitary
2. Reducing dopamine release
3. Increasing prolactin levels

Question 10

Causes of growth hormone deficiency?

Answer 10

1. Hypothalamic/pituitary dysfunction -
2. tumors, radiation, traumatic injury, autoimmune diseases,
3. Genetic defects - Prade-Willi, Turner syndrome

Question 11

Clinical features of GH deficiency in children?

Answer 11

1. Newborns - micropenis, hypoglycaemia
2. Children - stunted growth, delayed puberty
   Nystagus, hypoglucaemia, retinal defects, moderately overweight

Question 12

Clinical features of GH deficiency in adults?

Answer 12

decreased muscle mass, decreased bone mineral density, baldness

Question 13

What are the investigations for diagnosis of GH deficiency?

Answer 13

low serum GH levels, low serum IGF-2

Question 14

What is the management of GH deficiency?

Answer 14

Daily injection with growth hormones