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Acromegaly.
Aetiology
GH hypersecretion occurring in adult life after epiphyseal closure results in acromegaly.
Pituitary tumour is the most common cause. Rare causes include excessive growth hormone secretion from pancreatic islet cell tumour, or excessive secretion of growth hormone-releasing hormone from hypothalamic lesions, bronchial carcinoid and small cell lung carcinoma.
Clinical features
Soft tissue changes Thickening of skin, increased skin tags, acanthosis nigricans, increased sweat and sebum resulting
in moist and oily skin, enlargement of lips, nose and tongue, increased heel pad thickness, visceral enlargement—e.g. thyroid, heart and liver, carpal tunnel syndrome, myopathy, sleep apnoea.
Bone changes - Large spade-like hands, large feet, prognathism, prominent supraorbital ridges, large frontal sinuses,
wide-spacing of the teeth, arthropathy, kyphosis.
Metabolic effects - Glucose intolerance or clinical diabetes mellitus.
Pressure effects - Refer pituitary tumour.
Cardiac effects - Coronary heart disease, cardiomyopathy, hypertension, left ventricular hypertrophy.
Others - Increased risk of colonic polyps and carcinoma.
Investigations
Investigations of pituitary tumour (refer pituitary tumour).
Elevated IGF-I (insulin-like growth factor-I) levels.
GH levels are measured during an oral glucose tolerance test. A failure of suppression or a paradoxical rise of GH indicates acromegaly.
Demonstration of GH rise after TRH administration.
Treatment
Surgery
Trans-sphenoidal surgical removal of adenoma.
Medical therapy
Primary treatment with drugs is indicated in:
those with no risk of visual impairment from the tumour;
those who are poor candidates for surgery;
those who decline surgery;
those with tumours unlikely to be controlled by surgery;
those who require the preservation of intact pituitary function (especially fertility).
Various drugs are:
Bromocriptine or cabergoline (dopamine agonist) are useful in those with mildly elevated IGF-I.
Octreotide or lanreotide (somatostatin analogue). Somatostatin analogues are more effective than dopamine agonists and act on pituitary somatostatin receptors to produce inhibition of GH and IGF-I.
Pegvisomant, a GH receptor antagonist, blocks peripheral IGF-I action in almost all patients, and is indicated in patients who are inadequately controlled with other modalities or in patients experiencing clinically significant drug side effects. Tumour size should be monitored at intervals, as the therapy is directed at blocking peripheral GH receptors and not at treating the pituitary tumour.
Radiotherapy
External radiotherapy or implantation of yttrium into the gland in patients not candidates for surgical therapy, and in whom medical therapy fails.
Others
Treatment of diabetes, hypertension and hyperlipidaemia.
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