EFFECTS OF THYROXINE ON GROWTH OF MAMMARY GLANDS, WHOLE BODY, HEART AND LIVER IN HYPOPHYSECTOMIZED RATS TREATED WITH INSULIN, CORTISONE AND OVARIAN STEROIDS

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Abstract
The effect of thyroxine on the growth of mammary glands and other tissues was studied in rats devoid of hypophysial hormones. 1. Experimental procedures permitting prolonged treatment of hypophysectomized rats with thyroxine together with long acting insulin, cortisone, oestradiolbenzoate and progesterone in doses inducing growth were worked out. It was found essential (1) to subject the rats to a fortnight''s pretreatment with thyroxine before superimposing the other hormones and (2) to avoid cortisone in doses larger than 0.25 mg daily. 2. Administration of thyroxine with or without cortisone to gonadectomixed hypophysectomized rats injected with oestradiolbenzoate and progesterone resulted in a development of end buds whilst other mammary tissues remained atrophic. 3. Thyroxine enhanced the growth reaction of the mammary glands to oestradiolbenzoate and progesterone in gonadectomized hypophysectomized rats treated with insulin and cortisone. 4. Determinations of the weight and length of the body and of the weight of the liver, heart ventricles and adrenal glands showed that thyroxine in the hypophysectomized rats treated with insulin, cortisone and ovarian steroids enhanced the growth of the body and heart ventricles. 5. The observations made in the present work support the view that the growth of the mammary gland is dependent upon the state of the general metabolism.