Gigantism and acromegaly are hormonal disorders that result from too much growth hormone (GH) in the body. In these conditions, the pituitary produces excessive amounts of GH. Usually the excess GH comes from benign, or noncancerous, tumours on the pituitary.
When GH-producing tumours occur in childhood, the disease that results is called gigantism. In response to GH, the long bones grow in length at the growth plate—areas near either end of the bone. Prolonged exposure to excess GH before the growth plates fuse causes increased growth of the long bones and thus increased height (Fig.2.1 & 2.2). In more than ninety percent of individuals, the underlying cause is a benign pituitary tumour. Occasionally it may present as a feature of other conditions such as multiple endocrine neoplasia (MEN) type I, McCune-Albright syndrome (MAS), neurofibromatosis, tuberous sclerosis or Klinefelter syndrome.
Since growth plates fuse after puberty, excessive GH production in adults does not result in increased height. It produces a condition known as acromegaly. The name acromegaly comes from the Greek words for “extremities” and “enlargement,” reflecting one of its most common symptoms—the abnormal growth of the hands and feet. Symptoms may include, coarse facial features as protruding jaw, enlarged lip, nose, and tongue (FIG.2.3), swelling of the hands and feet (Fig.2.4) degenerative arthritis, enlarged heart, fatigue and weakness, headaches, loss of vision, irregular menstrual cycles in women, diabetes and high blood pressure.
In few patients, acromegaly is caused not by pituitary tumours but by tumours of the pancreas, lungs and adrenal glands that also lead to an excess of GH either because they directly produce GH or, more frequently, because they produce GHRH. Mostly, the overproduction of GH is caused by a benign tumour of the pituitary gland.
The goal of treatment is to restore the pituitary gland to normal function, producing normal levels of growth hormone. Treatment may include removal of the tumour, radiation therapy, and injection of growth hormone blocking drugs.
Surgical removal of the pituitary gland tumour should be considered as the primary treatment for most patients with acromegaly. Medical therapy should be administered only to patients with persistent postoperative disease. Somatostatin (octreotide) and Dopamine-receptor agonists (eg, bromocriptine, cabergoline), and GH receptor antagonists (pegvisomant) are the mainstays of medical treatment. Radiation treatment usually is reserved for recalcitrant cases.
