Acromegaly, a
chronic disease of
growth hormone (GH) hypersecretion, is most typically caused by a
pituitary adenoma. Early diagnosis is critical for prompt intervention to prevent deleterious effects of prolonged exposure to elevated GH and
insulin-like growth factor Type I (
IGF-I) levels. Current
therapy for
acromegaly includes several options: surgery,
radiotherapy and
pharmacotherapy. Transsphenoidal adenomectomy remains a mainstay of
therapy for
acromegaly. Cure rates are high in microadenomas, but < 50% in macroadenomas. Conventional and stereotactic procedures for
radiation therapy are also effective in decreasing GH levels in acromegalic patients, but they need years to normalise GH hypersecretion and carry with them the risk of
hypopituitarism. The major classes of drugs currently used to treat
acromegaly are
dopamine agonists and analogues of
somatostatin.
Dopamine agonists bind to the D2 receptor and suppress GH hypersecretion in some patients with
acromegaly. Their clinical effectiveness is modest, although promising results have been obtained with two novel compounds,
quinagolide and
cabergoline, that possess long duration of action.
Somatostatin analogues have been shown to improve clinical symptoms of
acromegaly, decrease hypersecretion of GH and
IGF-I and reduce tumour volume in a clinically significant number of patients.
Octreotide is administered by s.c. route several times a day, but the recently developed
sustained release formulations (
octreotide LAR and SR
lanreotide) are administered only every 7-28 days by i.m.
injections. The complications associated with
somatostatin analogues are small, relative to the benefits. Lastly, compounds with a novel mechanism of action, the GH receptor antagonists, are presently under investigation.