Abstract
SUMMARY: 1. A study was made of the ovarian reaction to pregnant mares' serum (PMS) in adult thyroidectomized, thyroidectomized/adrenalectomized, adrenalectomized and intact rats. 2. Thyroidectomized animals responded more vigorously than did any other group. Adrenalectomized animals hardly responded at all. Animals that had been both thyroidectomized and adrenalectomized reacted almost as strongly as did non-adrenalectomized thyroidectomized animals, and slightly more than intact controls. 3. A histological analysis confirmed that thyroidectomy is associated with hypersensitivity to both follicle-stimulating hormone (FSH) and luteinizing hormone (LH), and that adrenalectomy in the adult is associated with an impaired response to FSH but not to LH. The ovaries of thyroidectomized/adrenalectomized animals contained more large Graafian follicles and more large corpora lutea than did those of adrenalectomized litter-mates. 4. The results appear to imply that the mechanisms mediating the changes in ovarian sensitivity to PMS after thyroidectomy and after adrenalectomy are independent of each other.