Steroid secretion by follicles and cysts from the hypothyroid, hCG-treated rat

Hypothyroid rats develop cystic follicles after daily administration of human chorionic gonadotropin (hCG). This study was undertaken to compare progesterone, testosterone, and estradiol secretion by antral follicles (0.9-1.0 mm) and cysts (small; 1.2-2.0 mm; large: > 2.0 mm) from hypothyroid, hCG-treated rats with that of antral follicles from euthyroid, saline-treated animals. After 3, 5, or 10 days of hCG injections, follicles and cysts were dissected from the ovaries, diameter determined, and incubated in minimum essential medium (MEM) for 2 hr at 37 degrees C. Media were assayed for progesterone, testosterone, and estradiol by RIA. Progesterone secretion by antral follicles removed after 3, 5, or 10 days was similar but small cysts secreted significantly more of this steroid than did antral follicles. Large cysts secreted significantly more progesterone than all other follicles and cysts. After 10 days of treatment with hCG, antral follicles from hypothyroid, hCG-treated rats secreted two to three times more testosterone than similar follicles from euthyroid, saline-treated animals. Changes in estradiol secretion were not apparent until after 10 days of hCG treatment. Both small and large cysts from those animals secreted significantly more estradiol than all other follicle and cyst groups. These results suggest that steroid secretion by follicles and cysts could be contributing to elevated serum levels of progesterone and testosterone during the first 10 days of cyst induction. However, cysts may be contributing estradiol only during the later stages of cyst induction.