Menstrual cycle disorders after therapy with iodine-131

Objective: To investigate any abnormalities of the menstrual cycle and/or pregnancy in women < 40 years old who had received radioiodine (I-131) therapy for thyroid cancer. Design: Case-control study. Setting: General military hospital in Athens, Greece. Patient(s): Forty-five women of childbearing age with thyroid cancer that were treated with I-131 from December 1996 to May 2003 were compared to 83 age-matched control females. Intervention(s): The patients' charts were reviewed, and in addition patients were contacted by telephone and asked detailed questions about their previous gynecologic history and any problems after treatment (menstrual cycle and pregnancy). Main Outcome Measure(s): Abnormalities of menstrual cycle and/or pregnancy. Result(s): Overall, 14 of 45 women (31.1%) had menstrual cycle irregularities after treatment. Eight patients (17.8%) had normal menstrual cycles before therapy and six (13.3%) had pretreatment menstrual cycle irregularities that persisted or were exaggerated after therapy. In the control group, 12 of 83 women (14.5%) reported menstrual cycle irregularities. The patients' menstrual cycle and menses irregularities were significantly increased after I-131 therapy (P = .02) compared with the control group and seemed to increase with age. After therapy a total of seven children were borne by 6 of the 45 patients (13.3%). No premature births or miscarriages were noted. Conclusion(s): The study found a significant increase of patients with menstrual cycle and/or menses irregularities after treatment with I-131. However, therapy with I-131 did not result in any subsequent pregnancy abnormalities such as premature births or miscarriages.