RELATION OF THYROID TO MAMMARY GLAND STRUCTURE IN THE RAT WITH SPECIAL REFERENCE TO THE MALE

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Abstract
The effects of thyroidectomy in normal and castrated [female][female] and [male][male] with inj. of certain gonadotrophic and sex hormones were studied in 60 rats. Immature [female][female] thyroidectomized for 48 days and then injected with 20 mg. of an extract of menopause urine over a 4-day period showed a reduced extension of the mammary gland duct system, and a marked increase of lobular-alveolar development. [male][male] were thyroidectomized and castrated at 25 days, and sacrificed at 65 days. Thyroidectomy in normal [male][male] resulted in inhibition of mammary duct growth and stimulation of alveolar development when compared with their controls. Thyroidectomy in castrated [male][male] brought about much the same structural changes, but to a lesser degree, when comparison was made with castrated controls. Thyroidectomized castrated [male][male] treated with 0.25 mg. of testosterone during the last 10 days had mammary glands with an exaggerated lobular-alveolar development, and inhibition of duct growth, when comparison was made with appropriate controls. Thyroidectomized castrated [male][male] treated with 50 gamma of estrogen over the last 10 days gave results indistinguishable from the testosterone treated group. Thus under these conditions, estrogen and testo- sterone exhibit similar effects on mammary growth. The general effects of thyroidectomy on mammary growth in immature rats are an inhibition of duct extension, and the production of a small compact type of gland with thickened ducts and a marked development of the lobular-alveolar system.