Changes of molecular forms of growth hormone in bromocriptine treated acromegaly in relation to changes of somatomedin-C and clinical response

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Abstract
Eleven patients with active acromegaly were treated with 10-20 mg bromocriptine [a dopamine agonist] daily for a period of 6-9 mo. The clinical response was evaluated by a ''clinical and metabolic improvement score''. The biochemical response was evaluated by measurement of both the mean plasma growth hormone (GH) level during the day and the somatomedin-C (Sm-C) concentration. Before and at the end of the treatment period plasma samples were fractionated by Sephadex G-100 chromatography in order to study the effects of chronic bromocriptine treatment on the concentrations of total GH and its different molecular forms. Three immunoreactive components were observed on Sephadex chromatography corresponding to MW > 100,000 (big-big GH), 40,000-60,000 (big GH) and 20,000-22,000 (little GH). Bromocriptine treatment induced preferentially a reduction of little GH. There was a very good correlation between the decrease of little GH and total GH, and both were significantly correlated with the clinical response. The correlation between the decrease of Sm-C values and that of little and total GH as well as between the decrease of Sm-C and the clinical response was poor. Measurement of little GH is not superior to the determination of total GH in the assessment of disease activity of bromocriptine treated acromegalic patients. Both methods are superior to the measurement of plasma Sm-C levels. Clinical response out of proportion of the fall of total GH which can be explained by a preferential reduction of little GH, has not been observed in these investigations.