Plasma levels of estrone (E1), estradiol-17beta (E2), and estriol (E3), as well as follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin were measured in 30 control subjects and in 20 postmenopausal patients with adenocarcinoma of the endometrium. Within the sensitivity of the assay (5 to 10 pg.), no E3 was found. Mean levels of E1 and E2 in the patients with carcinoma (42.64+/-3.8 (S.E.M.) and 17.3+/-1.7 (S.E.M.) pg. per mililiter) were significantly higher than those measured in the control subjects (E1=26.97+/-2.4 (S.E.M.) pg. per mililiter, p less than 0.001; E2=12.08+/-1.2 (S.E.M.) pg. per milliliter, p less than 0.02). Effects of age, diabetic status, and obesity were taken into consideration. Significant differences in FSH and marginally significant differences in prolactin levels were observed between the two groups. Mean levels of FSH, LH, and prolactin in the control group and the group with adenocarcinoma, respectively, were as follows: FSH=152.3+/-7.0 (S.E.M.) versus 98.1+/-8.9 (S.E.M.) mI.U. per milliliter, p less than 0.001; LH=64.7+/-3.1 (S.E.M.) versus 66.5+/-5.2 mI.U. per milliliter, difference not significant; and prolactin=14.3+/-0.9 (S.E.M.) versus 17.8+/1.7 (S.E.M.) ng. per milliliter, p less than 0.06. These results, as well as previously reported alterations in human growth hormone secretion, suggest aberrations in hypothalamic function in endometrial carcinoma.