Dyslipidemia in South African patients with hypothyroidism

Abstract

Background: Overt hypothyroidism leads to increased cardiovascular risk, primarily through effects the disorder has on lipids. Most studies investigating lipids in the setting of hypothyroidism, have been performed in predominantly Caucasians in North America and Europe. Different patterns and prevalence of dyslipidemia have been described; one study reporting dyslipidemia in 90% of patients with hypothyroidism. The prevalence of dyslipidemia in overt hypothyroidism among the ethnically diverse predominantly black South African population is unknown.

Methodology: A retrospective case-control study evaluating lipid profiles of an ethnically diverse cohort of patients with overt hypothyroidism (TSH > 10 mIU/L) attending two academic hospitals in Johannesburg, South Africa from September 2006-September 2016. Patients with primary or secondary causes for dyslipidemia and those taking lipid-lowering therapy were excluded.

Results: Two hundred and six patients with hypothyroidism were included and compared to 412 euthyroid controls matched for sex, ethnicity, and age. Most hypothyroid patients were female (n = 180;67.5 %). Median TSH was similar across all ethnic groups (p = 0.09). Median TC, TG and LDL-C were higher in hypothyroid patients (p < 0.01). Normal lipid profiles were found in 29.44 % of all hypothyroid patients. However, a greater proportion, 47 of 124 (37.90 %), black African patients with hypothyroidism had a normal lipid profile.

Conclusion: Dyslipidemia is less common in black African patients with hypothyroidism. This is probably due to this population group being in an earlier stage of epidemiologic transition. Those with hypothyroidism were at greater overall cardiovascular risk based on TC/HDL-C ratio but did not reach high risk atherogenic profiles reported in previous studies.

Keywords: Dyslipidemia; Ethnicity; Hypercholesterolemia; Hypothyroidism.

Fig. 1

Scatter plot with fit lines showing the positive relationship between TSH and TC in black African (ρ = 0.345, n = 139, p < 0.01) and Caucasian patients (ρ = 0.277, n = 42, p = 0.04) with hypothyroidism.

Fig. 2

Scatter plot with fit lines showing the positive relationship between TSH and LDL-C in black African (ρ = 0.291, n = 124, p < 0.01) and Caucasian patients (ρ = 0.207, n = 42, p = 0.10) with hypothyroidism.

Fig. 3

Scatter plot with fit lines showing the negative relationship between FT4 and TC in black African (ρ = -0.344, p < 0.01) and Caucasian patients (ρ = -0.410, n = 29, p-value indeterminate due to small sample size) with hypothyroidism.