Effects of menstrual cycle showing infradian rhythm on thyroid blood flow and thyroid volume in healthy women

The aim of the present study was to determine alterations in thyroid blood flow parameters and thyroid volume (TV), measured at inferior thyroid artery (ITA), due to changes in sex hormones and thyroid stimulating hormone (TSH) at four different periods of menstrual cycle (MC) showing infradian rhythm in healthy women. Twenty-two women with regular MC were recruited. Individuals were assessed with hormone levels, and Doppler ultrasound (US) findings at days 3, 7, 14, and 21 of MC. Mean TSH, peak systolic velocity (PSV), resistance index (RI), pulsatile index (PI), and TV were statistically analyzed. Compared to days 3 and 7, significant increases were detected in TSH, TV, and PSV at day 14 (p = 0.005, p = 0.000, p = 0.014; and p = 0.021, p = 0.002, p = 0.021, respectively). No significant differences were found for PI at different periods of MC (p > 0.05). RI significantly decreased at days 14 and 21 when compared to day 3 (p = 0.020 and p = 0.015, respectively). Alterations occur in ITA blood flow parameters and TV along with TSH levels throughout the MC.