EFFECTS OF OESTROGEN ON PITUITARY FUNCTION IN THE THYROIDECTOMIZED RAT

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Abstract
The effects of estrogen administration on normal and thyroidectomized male rats were studied and compared with control groups. Determinations of trophic hormones in plasma and anterior pituitary glands were attained by bioassay procedures. In the intact rat injected with estrogen, the growth hormone content of the anterior pituitary gland was decreased, whereas in the thyroidectomized male rats the content was elevated to levels above normal. It was found that the growth promoting potency of plasma from thyroidectomized male animals could be restored to normal levels by the administration of estrogen. The administration of estrognn to the thyroidectomized rat did not affect the TSH (thyroid-stimulating hormone) content of pituitary glands or plasma, whereas in the intact rat, resulted in a decrease in the TSH content of the pituitary gland. Administration of estrogen decreased the gonadotropic content of the pituitary gland in the normal and thyroidectomized rat. Pituitary glands from thyroidectomized rats injected with estrogens showed reappearance of acidophils coupled with the typical development of post-thyroidectomy basophils.