Thyroid functions and insulin resistance in pregnant Sudanese women

The thyroid function test (free triiodothyronine [FT3], free thyroxine [FT4], and thyroid-stimulating hormone [TSH]) is one of the key determinant of glucose homeostasis by regulating the balance of insulin. Thyroid dysfunction alters glucose metabolism, leading to insulin resistance (IR). This study aimed to assess the association between thyroid function and IR in pregnant Sudanese women.

A cross-sectional study was conducted in Saad Abuelela Hospital, Khartoum-Sudan, from January to April 2021. Obstetric/sociodemographic characteristics were gathered through questionnaires. Serum TSH, FT3, FT4, fasting plasma glucose (FPG), and fasting insulin levels were measured and evaluated, and IR was estimated using the homeostatic model assessment for insulin resistance (HOMA-IR) equation.

In total, the study included 127 pregnant women with a median age of 27.0 years (interquartile range [IQR] 23.0‒31.2) and a median gestational (IQR) age of 25.0 (IQR 25.0‒27.0) weeks. The medians (IQRs) of the TSH, FT3, and FT4 were 1.600 (1.162‒2.092) IU/ml, 2.020(1.772‒2.240) nmol/l, and 10.70 (9.60‒11.90) pmol/l, respectively. The median (IQR) of the FPG and fasting blood insulin level was [69.0 (62.00‒78.00) mg/dl] and [5.68(2.99‒11.66) IU/ml], respectively. The median (IQR) of the HOMA-IR level was 0.9407 (0.4356‒2.1410). There was a positive correlation between HOMA -IR and FT3 levels (r = 0.375; P < 0.001) and a negative correlation with FT4 levels (r= -0.312; P < 0.001). Also, a significant positive correlation was found between fasting insulin levels and FT3 levels (r = 0.438; P < 0.001) and a negative correlation with FT4 levels (r= -0.305; P < 0.001).

This study indicated that FT3 has positive correlation with HOMA-IR, while FT4 has negative correlation among healthy pregnant women without a history of thyroid dysfunction. This may indicate screening of euthyroid pregnant women for thyroid dysfunction and IR. Further studies are needed.