Gonadal hormones and thyroid function in the spotted munia, Lonchura punctulata

Abstract

Female and male spotted munia, Lonchura punctulata, were gonadectomized in February, and their thyroid function was studied 4 (June) and 7 (September) months later. There was no effect on the thyrodial 131I uptake, plasma protein-bound iodine (PBI), and proportions of radioiodoamino acids in the thyroid gland hydrolyzates of ovariectomized birds at any time. The maximal thyroidal 131I uptake was increased and PBI decreased temporarily after radioisotope administration in orchidectomized birds in June, but the time curves of these two parameters were not affected in September. The maximal 131I uptake in ovariectomized and orchidectomized birds were both lower in September as compared to June. Administration of estradiol benzoate (EB) and testosterone propionate (TP) into normal and gonadectomized adult birds failed to alter the proportions of radioiodoamino acids in the thyroid gland. Estradiol injection in intact juvenile females led to decrease in 131I uptake and increase in PBI without any apparent effect on hormonogenesis. Administration of TP into intact juvenile males resulted in increased thyroidal 131I uptake and decreased PBI, but the intrathyroidal conpounds were not affected.