Disorders of Anterior Pituitary MCQs

The growth promoting effects of GH is largely mediated via IGF1. The metabolic actions of GH like hyperglycaemia, hyperlipidemia, hypertriglyceridemia, nitrogen retention and lipolysis is independent of IGF1. GH impairs glucose tolerance by antagonizing insulin action. IGF-1 apart from binding to its own receptor, can also act on insulin receptor which is responsible for the hypoglycemic episodes. While, injected IGF-I induces hypoglycemia, and lower doses improve insulin sensitivity in patients with severe insulin resistance and diabetes. Reference : Harrison's Principles of Internal Medicine 21 st edition Page 2894

In acromegaly, the features of disease activity are: headache progressive deterioration of visual field uncontrolled diabetes increased sweating increasing joint pain uncontrolled hypertension Reference : Harrison's Principles of Internal Medicine 21 st edition Page 2913

Lanreotide is a long-acting somatostatin analogue which specifically stimulates SSTR 2. Stimulation of the somatostatin receptor leads to inhibition of production of a number of hormones including gastrin, cholecystokinin, glucagon, growth hormone, insulin and secretin. Somatostatin analogues are used for the medical treatment of acromegaly, pre-surgery or after surgery of radiotherapy for persistently elevated growth hormone levels. They are also used for symptomatic relief of the carcinoid syndrome. Reference : Harrison's Principles of Internal Medicine 21 st edition Page 2913

We would not expect ADH levels to be affected by a prolactinoma, and production of ACTH, TSH and growth hormone should not be affected by a microprolactinoma, as it is usually macroadenomas that cause pressure effects , suppressing production of other hormones. Hyperprolactinemia suppresses release of gonadotropin releasing hormone, which leads to reduced production of LH and FSH. There may also be a direct effect of prolactin itself on the ovary to disrupt LH and FSH signaling. Reference : Harrison's Principles of Internal Medicine 21 st edition Page 2908

The growth spurt at puberty is brought about by the secretion of androgens in the male and estrogens in the female. However, it is estrogens that ultimately terminate growth by causing the epiphyses in the long bones to fuse. Thus, estrogens rather than androgens are responsible for skeletal maturation, epiphyseal fusion and cessation of growth in males and females. Growth hormone, thyroxine and insulin are involved in growth alone. Reference : Harrison's Principles of Internal Medicine 21 st edition Page 2912

Men with prolactinoma tend to present substantially later than women, the latter presenting with cessation of periods and galactorrhoea. Macroprolactinoma is unlikely given his normal visual fields. Prolactinoma is the most common pituitary tumor; Microadenomas are more common in women, whereas macroadenomas appear more commonly in men. Prolactin levels less than 100 ng/ml could be drug induced or as a part of stalk effect due to pituitary tumor compressing on stalk. Prolactin levels more than 100 ng/ml is suggestive of prolactinomas Prolactin levels more than 250 ng/ml is suggestive of macroprolactinoma (adenoma size > 1 cm) Medical therapy with dopamine agonists (cabergoline, bromocriptine) is preferred over surgical management of prolactinomas. Reference : Harrison's Principles of Internal Medicine 21 st edition Page 2910

She most likely has a microprolactinoma , which would appear as a hypointense area on MRI scanning. Serum prolactin is often in the range 1500 mU/l to 3000 mU/l in patients with microadenomas; levels are usually above 3000 mU/l in those with macroadenomas. Prolactinomas show excellent response to cabergoline with normalisation of serum prolactin in >90% cases. Reference : Harrison's Principles of Internal Medicine 21 st edition Page 2910

Pegvisomant is a GH analogue that antagonizes endogenous GH action by blocking peripheral GH binding to its receptor. Consequently, serum IGF-I levels are suppressed, potentially reducing the deleterious effects of excess endogenous GH. Cabergoline suppresses GH. Bromocriptine and Cabergoline suppresses GH secretion particularly those with concomitant elevation of serum prolactin. Lanreotide and Octreotide are SSTR2 analogues that reduce both GH and IGF1 levels. Reference : Harrison's Principles of Internal Medicine 21 st edition Page 2913