Subclinical Hypothyroidism (SH) and Atherogenic Index of Plasma (AIP) in Women: A Case-Control Study From a Tertiary Care Hospital in South India

Abstract

Introduction Subclinical hypothyroidism (SH) is defined as an increase in serum-thyroid stimulating hormone (S-TSH) above the normal level with free triiodothyronine (T4) and free thyroxine (T3) within the normal range. It is more common in females. The association between SH and dyslipidemia is unclear. There are many controversial studies regarding the same. This is the single largest study of Atherogenic index of plasma (AIP) in SH among women from our country. Our aim is to study the lipid profile and AIP in SH patients. We will also study the correlation between AIP and S-TSH levels in SH patients. Materials and methods It was a retrospective study conducted in a tertiary care center. A total of 97 females with SH were taken as cases and 86 normal females were taken as euthyroid (ET) controls. They were matched for demographic characteristics. T3, T4, S-TSH, total cholesterol, S-triglycerides (S-TG), high-density lipoprotein - cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and AIP were compared between the two groups. Spearman’s correlation between TSH and AIP was studied in the SH group. Mann-Whitney U test was performed. Results The TG, HDL, AIP levels were significantly different between both groups. TG, AIP was higher in the SH group compared to the ET group (p value of TG= 0.01, p value of AIP <0.0001). HDL was lower in the ET group compared to the SH group (p value <0.0001). AIP showed a significant positive correlation with S-TSH levels in the SH group. (r value=0.72, p value=<0.001). Conclusion It is important to regularly monitor SH patients for dyslipidemia, in order to start early therapy with levothyroxine/statins. Emphasis should be laid on lifestyle changes such as diet and exercise from the time of diagnosis. Community level education and awareness should be encouraged. Also, AIP is a better parameter to assess cardiovascular risk in SH patients than a conventional lipid profile.

Assessment of Cardiovascular Disease Risk in Females with Subclinical Hypothyroidism

“…The elevated AIP among subclinical hypothyroidism is due to increased TG and decreased HDL-C compared to normal euthyroid control. The mean AIP of subclinical hypothyroid females revealed that SCH females were at higher risk for cardiovascular disease than euthyroid females [25].…”

“…The decrease in fT3 and fT4 is characterized by primary hypothyroidism with increased serum TSH due to a feedback mechanism by the hypothalamus-pituitary-thyroid axis [25]. The diagnosis of subclinical hypothyroidism is based on laboratory variables as the patient does not show symptoms, unlike with primary hypothyroidism.…”

“…Our study depicted the correlation between TSH and lipid indices, where TSH showed a significant positive correlation with AIP only (r = 0:256 and p = 0:010). Madhura et al [25] pictorialized a significant positive correlation between TSH and AIP in SCH females. It revealed that the increased level of TSH elevated the risk of cardiovascular diseases.…”