Incidence of thyroid cancer in women in relation to previous exposure to radiation therapy and history of thyroid disease.

Female residents of 13 counties of Western Washington, in whom papillary, follicular, or mixed papillary-follicular thyroid carcinomas had been diagnosed between 1974 and 1979 were interviewed regarding their medical and reproductive histories and past exposure to radiation treatments. For comparison, a random sample of women from the same population was interviewed. Women who had received radiation treatments to the head or neck prior to 5 years before interview were 16.5 times (95% confidence interval = 8.1-33.5) more likely than unexposed women to develop cancer. The relative risk (RR) was highest for papillary cancer (19.4) but also was elevated substantially for follicular and mixed papillary-follicular tumors. Women first irradiated at age 19 years or younger had a much higher RR than did women irradiated at age 20 or older. Regardless of prior radiation exposure, women who ever had had a goiter were at increased risk of developing thyroid cancer. Women who had ever developed a goiter had 17 times the risk of developing follicular cancer and almost 7 times the risk of developing papillary cancer as compared with women who never had had a goiter. Risk of thyroid cancer was elevated even among women who had had a history of goiter many years prior to diagnosis. A history of thyroid nodules was also a risk factor for papillary and mixed thyroid cancer. Neither a history of hypothyroidism nor hyperthyroidism was found to increase the risk of thyroid cancer.

Incidence of thyroid cancer in women in relation to reproductive and hormonal factors.

Female residents of western Washington state aged 18-80 years in whom thyroid cancer was diagnosed between January 1974 and December 1979 were interviewed concerning their reproductive histories and their prior use of exogenous estrogens. Their responses were compared with those of a sample of women from the same population, individually matched to cases on telephone prefix. Use of each of several estrogen-containing preparations was associated with a small increased risk of thyroid cancer; parous women who had ever used a lactation suppressant had 1.7 times the risk of parous nonusers (95% confidence interval, 1.1-2.8); ever users of oral contraceptives had 1.6 times the risk of never users (95% confidence interval, 0.98-2.5); and ever users of postmenopausal estrogens had 1.4 times the risk of never users (95% confidence interval, 0.89-2.3). Among the low risk group of women, i.e., those who had never undergone radiation therapy and who had never had a goiter, a history of one or more pregnancies was also associated with a small increase in the risk of thyroid cancer (relative risk = 1.8, 95% confidence interval, 1.1-3.1). However, no increase in risk with increasing duration of use of oral contraceptives or menopausal estrogens or with increasing number of pregnancies was noted. While pregnancy and use of exogenous estrogens have an impact on the production of thyroid-stimulating hormone, their effect on the incidence of thyroid carcinoma, if present at all, appears to be small.

PIP: Female residents of western Washington state between 18-80 years of age in whom thyroid cancer was diagnosed between January 1974-December 1979 were interviewed concerning their reproductive histories and their prior use of exogenous estrogens. Their responses were compared with those of a sample of women from the same population, individually matched to cases on telephone prefix. Use of each of several estrogen-containing preparations was associated with a small risk of increased thyroid cancer; parous women who had ever used a lactation suppressant had 1.7 times the risk of parous nonusers (95% confidence interval, 1.1-2.8); ever users of oral contraceptives (OCs) had 1.6 times the risk of never users (95% confidence interval, 0.98-25.5); and ever users of postmenopausal estrogens had 1.4 times the risk of never users (95% confidence interval, 0.89-23). Among the low risk group of women; i.e. those who had never undergon radiation therapy and who had never had a goiter, a history of 1 or more pregnancies was also associated with a small increase in the risk of thyroid cancer (relative risk-1.8, 95% confidence interval, 1.1-3.1). However, no increase in risk with increasing duration of OC use of menopausal estrogens or with increasing number of pregnancies was noted. While pregnancy and use of exogenous estrogens have an impact on the production of thyroid-stimulating hormone, their effect on the incidence of thyroid carcinoma, if present at all, appears to be small.

Oral contraceptive use and the occurrence of pituitary prolactinoma.

To determine whether prior oral contraceptive (OC) use is a risk factor for pituitary prolactinoma, we attempted to identify all women (n = 72) with a prolactinoma diagnosed between 1976 and 1980 in three counties in western Washington. A control group of 303 women was selected by dialing random telephone numbers from the same counties. Prior OC use, according to OC indication, was ascertained during a standardized telephone interview. Relative to the risk for women who had never used an OC, the risk of prolactinoma for women who had used OCs for birth control was 1.3 (95% confidence interval, 0.7 to 2.6). This risk was 7.7 for women who used OCs for menstrual regulation (95% confidence interval, 3.7 to 17.0). Previous findings of an association between OC use and prolactinoma may have resulted from OC treatment of menstrual irregularity in women with an undiagnosed prolactinoma.