Failure of cyproheptadine to affect calcium homoeostasis and PTH levels in primary hyperparathyroidism.

In this study we evaluated the influence of cyproheptadine treatment on serum PTH values, as well as serum Ca, Mg and P levels in patients with primary hyperparathyroidism. For this purpose, cyproheptadine was given in a dose of 4 mg orally every 4 hours during 10 consecutive days to six patients with primary hyperparathyroidism. Control fasting blood samples for PTH, Ca, Mg and P were obtained every other day for a week. Afterwards cyproheptadine treatment was applied as mentioned above. Then blood samples were taken on the 4th, 6th, and 10th day of treatment to determine serum PTH, Ca, Mg and P. Before treatment the mean PTH (+/- SE) values were 22.95 +/- 1.4 mlU/ml and during cyproheptadine treatment were 23.06 +/- 0.9, 22.95 +/- 0.8, 22.32 +/- 0.8 mlU/ml, respectively. There were no significant changes in serum PTH levels before and during treatment (P greater than 0.05). Also serum Ca, Mg and P levels remained unchanged. Our data suggest that cyproheptadine treatment does not affect calcium homoeostasis and serum PTH levels in primary hyperparathyroidism.