I-131 therapy for differentiated thyroid cancer leads to an earlier onset of menopause: Results of a retrospective study

Treatment with I-131 for differentiated thyroid cancer may give a follicle- damaging radiation dose to the ovaries. This damage to the ovarian function could shorten the fertile life span and advance the natural menopause. To address this issue, we studied retrospectively the menopausal age of 130 wo men treated with I-131 for differentiated thyroid cancer in our institution from 1974-1993. The menopausal age of women treated with I-131 for differe ntiated thyroid cancer after total thyroidectomy and subjected to suppressi ve L-T-4 therapy was compared with the menopausal age of a control group in cluding 127 goitrous women who were treated with suppressive L-T-4 for a co mparable period of time. The cumulative theraPeUtiC I-131 dose to cancer pa tients ranged from 1,110-40,700 MBq (mean +/- SD, 5,308 +/- 5,483 MBq; medi an, 3700 MBq). All patients chosen for the study were younger than 45 yr wh en first treated (i.e. first administration of I-131 and L-T4 for cancer pa tients, and institution Of L-T4 therapy for goitrous patients), and older t han 45 yr at the end of the study period. The menopausal status of both gro ups was assessed from the clinical records and compared using Kaplan-Meier survival analysis. The menopausal age of cancer women treated with I-131 an d suppressive L-T4 therapy was less than that of goitrous patients treated with suppressive L-T-4 therapy (P < 0.001). We could not detect any relatio nship between menopausal age and the age at the first or last I-131 dose or to the cumulative I-131 dose received. These data indicate that I-131 trea tment is probably associated with an earlier ovarian failure in thyroid can cer patients. Conceivably, the ovarian irradiation by I-131 might contribut e to the process of the follicular atresia, thus inducing earlier menopause .