In rats bearing Morris hepatoma No. 7777, serum levels of alpha fetoprotein (AFP) increased as tumour size increased. Hepatoma-bearing females remained in dioestrus once the tumour exceeded a cross-sectional area of 12cm2. The following changes were seen in tumour-bearing rats compared to control animals : uterine wet weight was significantly decreased, the uterine epithelial mucosa was lower, castration cells developed in the anterior pituitary, and there was a 3to 23-fold elevation in serum

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... strogen levels. We conclude that circulating oestrogen is bound to AFP in hepatoma-bearing female rats and that in this bound state it is unable to exert its normal physiological actions.