Estrogens are widely distributed in the body and moderately bound to plasma proteins. Estrogens are metabolized primarily in the liver and eliminated in the urine. Consequently, estrogens are contraindicated in patients with breast carcinoma, except in selected patients with metastatic diseases. Benefit versus risk should be determined individually. Estrogens are contraindicated in patients with abnormal and undiagnosed vaginal bleeding because this may indicate the presence of endometrial hyperplasia or carcinoma, the growth of which would be promoted by the estrogen.
Estrogens are relatively contraindicated in patients with hypercalcemia.
Administration of estrogen in patients with breast cancer can cause severe hypercalcemia. Estrogens are relatively contraindicated in thrombophlebitis or in patients with thromboembolic disease. A positive relationship between estrogen dosage and thromboembolic disease has been demonstrated. Tobacco smoking is an additional risk factor for a thromboembolic event occurring in patients receiving estrogen therapy. Estrogens should be prescribed cautiously to patients who are cigarette smokers.