Based on our study, we found no correlation between TSH levels and lipid profile components. We also found no difference in mean levels of serum lipid levels between euthyroid and subclinical hypothyroid patients.
In a study by Unal E et al on 38 subclinical hypothyroid children in comparison to a control group, Subclinical hypothyroidism lead to an increased dyslipidemia (increased TC and LDL)[23] and in a study by Witte T et al showed that there is significant positive association between TSH and all non-HDL parameters (total cholesterol, LDL-C, and triglycerides) in children.[24] Another study by Cerbone M showed that triglyceride to high-density lipoprotein-cholesterol ratio (P = 0.01), and high-density lipoprotein-cholesterol were significantly lower (P = 0.003) in SH subjects compared with controls.[25]
In the study by Paoli-Valeri M et al on 17 children with subclinical hypothyroidism, subjects with subclinical hypothyroidism had significantly lower HDL-C levels.[26]. In the latest study by Dahl AR, et al on 228 children with subclinical hypothyroidism showed that Mild SCH in children and adolescents was associated with higher rates of elevated total cholesterol and elevated non-HDL cholesterol.[27].
Meanwhile, Nader NS et al argued that in euthyroid children without a history of hypo- or hyperthyroidism, increasing levels of TSH and decreasing levels of free T4 are associated with higher triglyceride levels[28] and Gönül Çatlı et al, in a study on 27 subclinical hypothyroid children comparing to a control group, showed that there is similar Serum lipoprotein levels and dyslipidemia frequency between the two groups.[30].
According to our results there is no relation between mean TC, LDL-C, HDL-C, non HDL-C and TG levels in euthyroid and subclinical hypothyroid children. The same results is found in the subsequent 2–10 and 10–18 year old age groups.
There is no statistical difference between the percentage of children who have high TC, LDL-C, Non-HDl-c and TG in euthyroid and subclinical hypothyroid children. No statistical difference was also shown in percentage of children with low HDL-c between euthyroid and subclinical hypothyroid children.
According to Berenson GS, et al, in the Bogalusa Heart study, atherosclerosis will start at childhood and the effect of multiple risk factors on the extent of atherosclerosis was quite evident. One of the major risk factors in atherosclerosis is hyperlipidemia.[31]
Although L-T4 treatment exerts some beneficial effects, there is no available data regarding the impact of therapy on metabolic outcomes in SH children.[25, 30]
The mechanism of how thyroid hormones can affect lipid profile is not completely clear, but thyroid hormones reduce apoB lipoproteins via a non-LDLR pathway that leads to decreased liver apoB production.[32]
Although it is generally believed that thyroid hormones and their synthetic derivatives known as thyromimetics, can reduce serum cholesterol by their ability to increase LDLRs but recent study showed that TH and thyroid hormone receptor-β selective agonists GC-1 and KB2115 are able to reduce serum cholesterol by inducing Cyp7a1 expression and stimulating the conversion and excretion of cholesterol as bile acids.[33].
The advantage of our study relative to other studies is that a large number of subclinical hypothyroid children are included and also this is a cross sectional prospective study. Most of the other studies on relation of TSH and serum lipid concentration are case control studies spanning several years.