Plasma homocysteine concentrations and serum lipid profile as atherosclerotic risk factors in subclinical hypothyroidism

Abstract

BACKGROUND AND OBJECTIVESBecause subclinical thyroid dysfunction may be a risk factor for cardiovascular disease, we evaluated the atherosclerosis tendency in subclinical hypothyroid (SCH) patients.PATIENTS AND METHODSFifty-three subclinical hypothyroid patients (serum thyrotropin [TSH] concentrations >4.12 mU/L) were compared with a control group of 50 euthyroid subjects whose age, sex and body mass indices were similar to the patient group. We tested whether serum TSH concentrations were correlated with plasma total homocysteine concentration (tHcy), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC) and triglycerides (TG).RESULTSThere was a significant statistical difference between the patient and control groups for normal free T4 (1.02±0.17 vs. 0.86±0.13, P<.001), TSH (1.64±1.02 vs. 6.62±2.61, P<.001), TC (185±39 vs. 206±42, P=.01), TG (103±54 vs. 132±85, P=.04), LDL-C (114±33 vs. 127±36, P=.04), and TC/HDL-C (3.81±106 vs. 4.19±1.02, P=.04), respectively. No statistically significant difference was found between the two groups for HDL-C, VLDL-C, LDL-C/HDL-C, and tHcy. Serum TSH was significantly correlated with plasma tHcy (r=0.55; P=.001), TC (r=0.52; P=.001), LDL-C (r=0.49; P=.001), TC/HDL-C (r=0.38; P=.002) and LDL-C/HDL-C (r=0.36; P=.004) across all participants.CONCLUSIONOur study suggests that the atherogenicity of SCH is not mediated by hyperhomocysteinemia. Associated hyperlipidemia may explain the observed increased risk of coronary artery disease in patients with SCH.

Evaluation of Selected Atherosclerosis Risk Factors in Women with Subclinical Hypothyroidism Treated with L-Thyroxine

“…L-thyroxine substitution brought some improvement in atherosclerosis indexes; however, the de-crease was only statistically significant in overt hypothyroidism group in LDL-C/HDL-C ratio. Some authors reported a similarly beneficial influence of hormone therapy on LDL-C/HDL-C ratio [17], but others failed to show such relations [18]. As for atheroprotective HDL particles, their concentration was lower in both hypothyroidism groups vs. controls in our study.…”

Thyroid-stimulating hormone decreases HMG-CoA reductase phosphorylation via AMP-activated protein kinase in the liver

“…The HepG2 cells stimulated by different concentrations of bTSH (0, 1, and 4 M) were homogenized with a loose-fi tting Tefl on pestle in 4 vol of 3 mM TrisHCl buffer (pH 7.4) containing 0.25 M sucrose, 0.1 mM EDTA, and Subclinical hypothyroidism is a type of thyroid function abnormality; its characteristics are elevated serum thyroidstimulating hormone (TSH) and normal serum thyroid hormone levels, as well as an increased serum cholesterol level ( 10 ). Our study and other clinical studies have addressed a positive correlation between the high serum TSH and increased cholesterol levels ( 11,12 ). Additionally, our laboratory data have shown that the TSH receptor (TSHR) was expressed in hepatocytes and the TSH could enhance the expression of HMGCR by activating the cAMP/PKA pathway, leading to an elevated cholesterol level via the TSHR in the hepatocytes ( 13,14 ).…”

A novel role for thyroid-stimulating hormone: Up-regulation of hepatic 3-hydroxy-3-methyl-glutaryl-coenzyme a reductase expression through the cyclic adenosine monophosphate/protein kinase A/cyclic adenosine monophosphate-responsive element binding protei

“…Several clinical studies in recent years addressed this issue and showed a correlation in hypothyroidism between high serum cholesterol and high TSH levels, the latter being usually used as an indication of the severity of the hypothyroidism. [5][6][7] In these studies, however, it was impossible to delineate a direct role of TSH as abnormal TH level (usually deficiency) was usually a coexisting factor. Thus, a molecular mechanism by which TSH might affect cholesterol level has never been established.…”