IntroductionPregnancy leads to changes in hormonal levels and lipid profile. Thyroid hormones play a crucial role in embryonic growth and fetal development. Untreated thyroid disease during pregnancy can lead to a high risk of complications.AimThe aim of the study is to examine the correlation between thyroid stimulating hormone (TSH) and lipid profile in pregnant women with hypothyroidism.Materials and methodsThis cross-sectional case-control study was conducted at the Biochemistry Department, Alfalah School of Medical Science & Research Centre, Dhauj, Faridabad, Haryana, India. The study consisted of 500 patients (250 cases and 250 controls) who fulfilled the inclusion and exclusion criteria. Of the 250 cases recruited, 23 cases were in the 2nd trimester and 209 cases were in the 3rd trimester. Blood samples were collected from the participants to assess their lipid profile and TSH levels.ResultsThe study showed a statistically significant difference between the mean TSH levels of hypothyroid pregnant females in the 2nd trimester (3.85 ± 0.59) and the 3rd trimester (4.71 ± 0.54). There was a significant positive correlation observed between TSH and Total Cholesterol, Triglycerides, and LDL-C in both the 2nd and 3rd trimesters. In the second trimester, there was a significant positive correlation observed between TSH & TC (r = 0.6634, p<0.0005), TSH & TG (r= 0.7346, p=0.00006), TSH & LDL (r= 0.5322, p= 0.008). In the third trimester, there was a significant positive correlation observed between TSH & TC (r = 0.8929, p<0.00001), TSH & TG (r= 0.430, p<0.00001), TSH & LDL (r= 0.168, p= 0.015). However, no significant correlation was found between TSH levels and HDL-C in either trimester. The correlation coefficient and p-value for TSH & HDL were r = 0.2083, p=0.340 in the second trimester, and r = 0.0189, p=0.2384 in the third trimester.ConclusionA significant increase in TSH levels in hypothyroid pregnant women was observed in the 3rd trimester compared to the second trimester. Moreover, a significant positive correlation was found between TSH and lipid profile (total cholesterol, triglycerides, and LDL) in both trimesters, but not with HDL. These findings highlight the importance of monitoring thyroid hormone levels in the later stages of pregnancy to avoid potential maternal & fetal complications.