CHANGES IN CIRCULATING SOMATOMEDIN-C LEVELS IN BROMOCRIPTINE-TREATED ACROMEGALY

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Abstract
To determine whether the improvement in clinical status of patients with active acromegaly correlates with a reduction of circulating somatomedin-C, serum immunoreactive somatomedin-C was measured in 27 patients before and during bromocriptine therapy. The patients were assessed using a clinical and metabolic score which included both subjective criteria of improved sweating and facial features, and objective criteria of a reduction in ring circumference and the area under the glucose tolerance curve. Using this, together with the change in GH [growth hormone] levels before and during bromocriptine therapy, the patients could be divided into 3 groups. In 1 group, there was no clinical improvement, a less than 30% decline in somatomedin-C, and in 4 of 6 patients no significant decline in GH. In both of the other groups there was clinical improvement and a greater than 30% decrease in somatomedin-C. In 1 of these 2 groups, however GH did not decline, while in the other it was reduced significantly. Apparently during bromocriptine treatment of acromegaly, serum somatomedin-C concentrations correlate better with clinical status than does serum GH. Since some patients have no significant fall in GH but show both clinical improvement and a reduction in somatomedin-C, it seems likely that in some patients bromocriptine may improve acromegaly by a mechanism other than a simple decrease in total immunoreactive GH secretion.