HORMONAL MECHANISM OF IMMUNOPOTENTIATION IN MICE AFTER ORCHIDECTOMY

Orchidectomy of Balb C mice aged between 4-6 wk delayed the normal rate of thymic involution. Testosterone replacement after orchidectomy prevented this relative thymic enlargement, and testosterone supplements given to intact mice accelerated the normal rate of thymic involution. When hypopituitary, dwarf mice were given somatotropin and thyroxine alone there was no significant difference in the thymic weights of control or orchidectomized mice. When replacement therapy included gonadotropin, orchidectomy was associated with significant thymic hypertrophy. Passive transfer of serum from previously orchidectomized mice did not change the thymic weight of normal recipient mice. Testosterone apparently exerts a constant moderating effect on the thymus; the immunological effects of orchidectomy are probably due to the direct effects of androgen withdrawal.