The effect of the menstruel cycle, a sample of infradian rhythm, on thyroid volume and blood flow in healthy women

Aim: The aim of this study is to evaluate the changes in thyroid stimulating hormon (TSH) levels through four different periods of menstruel cycle which is a sample of infradian rhythm; and to investigate the relationship between thyroid volume and doppler parameters of inferior thyroid artery according to TSH and sex hormon alterations in healthy women. Materyal And Methods:Twenty two healthy women having regular menstrual cycles between 21 and 38 years were included in this study. Each participant was evaluated at the 3. day (menstruel bleeding period), 7. day (follicular phase), 14. day (periovulatory period) and 21. day (luteal phase) of their menstruel cycle. All examinations were performed after a 12 hours fasting time, between am 06:00-08:00. Blood samples were collected for plasma estradiol (E2), progesteron (PG), luteinizing hormone (LH), follicle stimulating hormone (FSH), thyroidstimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4),thyroglobuline (Tg). Conventional ultrasonography and doppler ultrasonography were carried out. Findings: Mean age of these 22 women was 28.72 ± 5.72 years. The statistical alternations of the mean values of TSH, Tg, peak systolic velocity (PSV), resistance index (RI), pulsatility index (PI) and thyroid volumes at the 3. day, 7. day, 14. day and 21. days of menstruel cycle were examined. It was detected that there was a statistically significant in TSH, thyroid volume and PSV at the 14. day compared to the 3. and 7. days. With a minimal increase at the 21. day; any statistically significant change could not be found in PI values during menstruel cycle. Compared with the 3. day; there was a statistically significant decrease in RI value at the 14. and 21. days. Also compared to the 3. day; there was a statistically significant increase in thyroglobuline levels at the 7. and 14. days. During menstruel cycle, there was no significant change in fT3 and fT4 levels. In addition; during this period, no statistically significant correlation was detected between TSH levels and LH, FSH, PG, E2, Tg levels; and yet between TSH levels and PSV, RI, PI, thyroid volume. Conclusion: Through menstruel cycle; with thyroid volume, TSH, and Tg, also same changes occur in blood flow parameters of inferior thyroid artery doppler measurements are used for differential diagnosis of certain thyroid diseases. According to our study results; we believe that it is appropriate to evaluate the female patients during the follicular phase while performing doppler ultrasonography or population studies. Keyword: Menstruel cycle, thyroid volume, thyroid blood flow