Failure of bromocriptine to alter the qualitative characteristics of human growth hormone in acromegaly.

The role of bromocriptine as a therapeutic agent for acromegaly is uncertain. In the present study we have attempted to determine whether bromocriptine therapy causes qualitative changes in plasma human growth hormone (hGH) in acromegaly. When eight paired samples obtained before and during bromocriptine therapy were filtered over Sephadex G-100 there was no difference in the elution profiles. When the "little" hGH peak from each of the eight paired samples was pooled, lyophilized, and assayed in both radioreceptor assay (RRA) and radioimmunoassay (RIA), the RRA/RIA before treatment was not different than during treatment. When bromocriptine in pharmacologically significant concentrations was incubated with cultured human lymphocytes in vitro, there was no alteration in hGH binding properties. These results demonstrate directly that bromocriptine does not change the form or receptor-reactive properties of plasma hGH and, further, that the drug does not alter at least one form of human growth-hormone receptor.