Effects of Estradiol and Dehydroepiandrosterone on the Reproductive Cycle of the Cow. II. Histology of Primary and Accessory Reproductive Organs, Pituitary, Thyroid, and Adrenal Glands

Histological examination of ovarian follicles from three heifers receiving daily injections of 250 to 350µg of estradiol for varying lengths of time revealed an abnormal or absent granulosa layer and a thickening and partial luteinization of the thecal layers. In one heifer injected daily with 3.5mg estradiol for 30 days prior to slaughter, all follicles larger than 1mm in diameter exhibited follicular atresia; no follicle exceeded 10mm in size. The percentage of granular small beta cells from the basophilic zone of the anterior pituitary was increased in the heifers receiving at least 350µg of estradiol daily. Cystic corpora lutea were present on the ovaries of three out of four animals injected daily with 20 to 80mg of dehydroepiandrosterone (DHA). The percentage of hyalinized small beta cells from the basophilic core of the anterior pituitary was increased with daily injections of at least 40mg of DHA. Epithelial cell heights of the thyroid, oviduct, cervix, uterine superficial and basal glands were greater in the animals treated with estradiol than in the animals treated with DHA. The differences in height were not significant (P