A twenty-four hour temporal variation in peripheral levels of testosterone and thyroid hormones in male buffaloes

Abstract

Hourly serum samples from four adult Murrah buffalo bulls of 5 to 6 years of age were analysed for testosterone, thyroxine and triiodothyronine by radioimmunoassay during a period of 24 hours. All four bulls exhibited three episodic peaks for testosterone with some variation in the time, duration and peak concentration of the hormone. The average testosterone concentration varied from 0.30 to 3.50 ng/ml of serum. Thyroxine levels varied from 20 to 40 ng/ml of serum among the four bulls. One clear-cut peak was observed between 2 and 5 a.m. in three of the four bulls. One animal showed a characteristic peak at 10 p.m. Triiodothyronine levels ranged from 1 to 2 ng/ml of serum and followed a similar trend as that of thyroxine except for an additional small peak between 6 and 9 p.m.