Pharmacological therapy for acromegaly: a critical review

The treatment of acromegaly has changed considerably over the last few decades. In the late 1970s, the introduction of the dopamine receptor agonists made it possible to reduce growth hormone (GH) secretion by somatotropinomas for the first time. Thereafter, the introduction of the somatostatin analogues in the early 1980s had major implications. Recently, the first data on the use of genetically engineered human GH receptor (GHR) antagonists that block GH actions have become available. These GHR antagonists reduce both the biochemical abnormalities of acromegaly, as well as improve clinical signs and symptomatology. In this article we firstly review available data on dopamine agonists. Currently these compounds should be considered in patients with a mixed GH-prolactin secreting pituitary adenoma and/or those in whom pre-treatment insulin-like growth factor (IGF)-I concentrations are below 750 microg/L. We then discuss the somatostatin analogues. These compounds are capable of achieving biochemical control of GH and IGF-I in 50-60% of patients and tumour shrinkage in some 30%. In particular, candidates for treatment with these compounds are those patients who have undergone an unsuccessful transsphenoidal operation or who await the therapeutic effect of external pituitary irradiation. In selected patients primary medical therapy with somatostatin analogues is certainly a feasible option. To date, pegvisomant is the only available member of a new class of drugs that was especially designed to block the GHR. Pegvisomant is the most effective treatment for normalising IGF-I concentrations and appears to have a good safety profile. However, liver function tests should be regularly monitored and tumour size should be closely followed. Finally, we propose a treatment algorithm for acromegaly.