The effects of hypo- and hyperthyroidism on the testes and anterior pituitary glands of cockerels

Abstract

The average thyroxine secretion rate of 2-week-old White Leghorn cockerels was estimated to be approximately 0.65 μg/100 gm body weight/day. Doses of thyroid hormone intended to produce a mildly hyperthyroid state were based on this value in order to avoid purely pharmacological effects. Hypo- and hyperthyroidism brought about by the administration of propylthiouracil (PTU) and thyroxine had no effect on the testis and pituitary weights of 14-day-old cockerels. Thyroxine injections also produced no effect on the uptake of radioactive phosphorus ( 32P) by the gonad. However, the uptake of 32P by the testes of hypothyroid birds was significantly greater than that observed in normal controls. This effect was abolished if in addition to the PTU the birds received daily injections of thyroxine. The results of general gonadotrophin assays indicated that a significant decline in pituitary gonadotrophic potency occurred following thyroxine treatment. No change in gonadotrophic potency was found using pituitary glands from hypothyroid cockerels. The administration of the thyrotrophic hormone (TSH) significantly increased the uptake of 32P by the testes of previously untreated 5-day-old chicks. The presence of gonadotrophic hormones in the TSH preparation may have been responsible for this effect. However, estimated levels of FSH and LH contamination were low enough to suggest that the TSH itself may have possessed some gonadotrophic properties.