Hepatotoxicity of the synthetic oestrogen hexoestrol in the female rat.

The synthetic oestrogen hexoestol is hepatotoxic to the female rat. Twenty-five animals were treated daily with hexoestrol at a dose of 60 mg/kg. Twenty-five more acted as controls. Five animals from each group were killed after 4, 12, 20, 30 and 40 days of treatment to permit serial evaluations of liver histopathology to complement serum biochemical investigations. There were no mortalities during the study and only modest external signs of toxicity. All the treated rats showed reductions in body weight and appetite and gains in liver weight. This latter effect was due to both cellular hypertrophy and hyperplasia. The principle finding of the liver histopathology was fatty change. This affected scattered individual cells, mainly in the midzonal region. All of the serum parameters of toxicity--which consisted of bilirubin, total protein, albumin, glycoprotein, alpha 2-macrofoetoprotein, and alkaline phosphatase--indicated liver impairment. Most of these also showed time-related changes consistent with an initial phase up to Day 20 of marked liver dysfunction superseded by a more adaptive phase thereafter. The hepatotoxicity described here seems sufficient to explain blood clotting defects observed elsewhere in oestrogen-treated rats.