Thyroid function during normal pregnancy and preeclampsia

Abstract

Baclground There is a need to establish trimester-specific reference ranges for T3, T4 and TSH in different communities. Neither Sudan nor other African countries had established trimester-specific reference ranges for TSH, flee T3 (FT3) and fiee T4 (FT4) in healthy pregnant women. Also changes in thyroid fiinction/antibodies profiles in preeclamptic patients are controversial and were never investigated before in Sudan. ;A_i21§ 0 To establish trimester-specific reference ranges for healthy pregnant Sudanese women. 0 To compare thyroid function/antibodies of patients with preeclarnpsia to healthy pregnant women. Sub|'ects and Methods First study In a longitudinal study, 63 women with singleton pregnancy were followed since early pregnancy until the third trimester in Saad Abu- Alela Hospital, Khartoum, Sudan, during the period January—October 2014. An equal number of age and parity matched non-pregnant women were enrolled as a control group. Basic clinical and obstetrics data were gathered using questionnaires. TSH, FT3 and FT4 were measured using TOSOH. Second study Thyroid hormones (T3, T4 and TSH) and antibodies (anti-TPO and anti- TG) of 55 apparently healthy pregnant women (HC) were compared with patients with mild (MP) and severe (SP) preeclampsia (n=55 for each group). Women with blood pressure 2 140/90 after 20 weeks of gestation, but not before, and 2 300 mg of protein/24-hour urine were defined as preeclarnptic. Diastolic blood pressures < 110 or 2110 mmHg were used to define mild and severe preeclampsia. Patients suffering from diseases or using drug that may affect thyroid, renal or hepatic functions were excluded in all studied subjects. Results First study Median (5-95 centile) of TSH, FT3 and FT4 were 1.164 (0.079—2.177) IU/ml, 4.639 (3.843— 6.562) pmol/1, 16.86 (13.02—31.48) pmol/l in the first trimester; 1.364 (0.540—2.521) IU/ml, 4.347 (3.425—5.447) pmol/1, 13.51 (11.04—3 1 .07) pmol/l in the second trimester, 1.445 (0.588—2.460) IU/ml, 4.132 (3.176—5.164) pmol/l, 12.87 (9.807—23.78) pmol/l in the third trimester, respectively. While TSH increased throughout trimesters, FT3 and FT4 were significantly higher in the first trimester compared to the second and third trimester. TSH, FT3 and FT4 levels were significantly lower in the pregnant compared with non-pregnant women (P < 0.001). Second study TSH of SP (l.5(1.0—1.9) mIU//ml) and MP (l.3(0.9 -2.1) m1U//ml) were lower compared to HC (2.3(1.9—2.6) mIU//ml, P < 0.001). T3 of SP (2.1(l .9—2.6) pg/ml) and MP (2.0(l .4—2.4) pg/ml) were higher compared to HC (0.7(0.5—1.3) pg/ml, P < 0.001). SP had increased anti-TPO (10.5(7.3—l3.4) IU/ml) while MP had decreased anti-TG (1 1.1(8.2—-13.2) IU/ml) compared to HC (8.3(6.4—10.1) and 11.4(8.5——13.8) IU/ml respectively, P 5 0.002). Linear regression confirms association between levels of thyroid hormones and preeclampsia (P < 0.01) but not a.nti-TPO, anti-TG antibodies, parity, gestational age, BMI or hemoglobin levels (P > 0.05). Conclusions First study The present study is the first to establish trimester-specific reference ranges of TSH, free T3 and fiee T4 in Sudanese women with nonnal pregnancy. Our results demonstrated that pregnancy is likely to suppress TSH, FT3 and FT4 levels in healthy women. Second study Sudanese patient with preeclampsia tend to have higher levels of FT3, FT4, TSH and anti-TPO antibodies and lower level of anti-TG antibodies, irrespective of parity, gestational age, BMI and hemoglobin levels.