Q&A: Woman With Features Of Acromegly

Gigantism and acromegaly are syndromes of excessive secretion of growth hormone (hypersomatotropism) that are nearly always due to a pituitary adenoma. Before closure of the epiphyses, the result is gigantism. Later, the result is acromegaly, which causes distinctive facial and other features.

In this article:
Acromegly
MCQ clinical scenario
MCQ answer
MCQ explanation

Acromegly

The diagnosis of acromegaly should be suspected in individuals who present with the typical clinical features of growth hormone (GH) excess, which include the enlargement during adulthood of the jaw (macrognathia), hands, and feet, which result in increasing shoe and glove size and the need to enlarge finger rings.

The facial features become coarse, with enlargement of the nose and frontal bones as well as the jaw, and the upper incisors may become spread apart. Despite the prominence of these findings at the time of diagnosis, the rate of change is so slow that few patients seek care because their appearance had changed.

Other features include cardiovascular disease, sleep apnea, type 2 diabetes, arthropathies, carpal tunnel syndrome, and problems directly related to the pituitary tumor size (headache, visual loss).

However, because acromegaly is rare, we suggest against screening patients with isolated sleep apnea, uncontrolled diabetes, arthropathy, or carpal tunnel syndrome (unless there is a clinical suspicion of the disorder).

MCQ clinical scenario

A 40 year old female presents to her physician with a goitre.

On examination, the physician finds signs suggestive of acromegaly including coarse oily skin, a large tongue, prognathism and a prominent supra-orbital ridge of the face. Examination of the hands revealed thick, spade fingers.

Which of the following should be the initial hormonal diagnostic investigation:

a) insulin levels
b) growth hormone
c) arginine levels
d) growth hormone releasing hormone
e) insulin-like growth factor 1 (IGF-1)

MCQ answer

The correct answer is E.
The best initial hormonal investigation to diagnose Acromegaly is assaying IGF-1.

MCQ explanation

Since Serum GH levels vary considerably in different individuals, and in the same person at different times, measurement of random or basal GH levels are not of value in making the diagnosis of acromegaly.

IGF-1 is a growth factor produced by the action of growth hormone on the liver, kidney, muscle, pituitary and GI tract. GH exerts its effects indirectly through IGF-1 (formerly called somatomedin-C). Serum levels of IGF-1 may be considered a mean of the 24 hour levels of growth hormone, and is not affected by the pulsatile release of GH. It is thus a useful screening test for acromegaly.

Suppression of GH levels by glucose is the confirmatory test for acromegaly (Suppression of GH levels to < 2 mcg/L by RIA or < 1 mcg/L by IRMA 60 - 120 minutes after a 100 gram glucose load is diagnostic). Rare cases of acromegaly may be caused by ectopic production of GHRH, but it's measurement is not needed routinely. As always, radiological investigation should follow biochemical diagnosis (partly because of the high prevalence of pituitary incidentalomas). MRI is the method of choice for imaging the pituitary because of it’s excellent resolution.