CASE REPORT Lipid Profile Alterations in Subclinical Hypothyroidism Monica Dias Cabral, MD,* Antonio Jose Leal Costa, MD, PhD,† Mario Santos, MD,‡ and Mario Vaisman, MD, PhD* Abstract: There is controversy regarding the clinical significance of subclinical hypothyroidism, and lipid changes are one of the abnor- malities described in this disease. The authors evaluated alterations in the lipid profile in a group of patients with subclinical hypothy- roidism. Fifty-two patients with subclinical hypothyroidism were compared with 98 healthy controls matched by body mass index, age, and sex. A third-generation thyroid-stimulating hormone assay and serum lipid levels—total cholesterol (TC), low-density lipopro- tein-cholesterol (LDL-c), triglyceride (TG), high-density lipopro- tein-cholesterol (HDL-c), apoprotein A, lipoprotein (a), apoprotein B (apo B), TC/HDL, and LDL/HDL ratio—were measured. Sub- clinical hypothyroid patients had higher (P  0.05) TC, LDL-c, TG, apo B levels, TC/HDL and LDL/HDL ratio compared with the control group. There were no differences in relation to HDL-c, apoprotein A, and lipoprotein (a). There was an association between subclinical hypothyroidism and TC 200 and TG 200 mg/dL; 55.7% of the patients had hypercholesterolemia as compared with 34.6% in the control group (P = 0.01) and 17.3% of patients had hypertriglyceridemia compared with 5.1% in the control group (P = 0.01). The authors conclude that subclinical hypothyroidism is associated with elevated cholesterol and triglyceride levels and high total cholesterol/HDL and LDL/HDL ratios. Key Words: subclinical hypothyroidism, lipids, atherosclerosis (The Endocrinologist 2004;14: 121–125) S ubclinical hypothyroidism is defined as a symptom-free or minimally symptomatic state that is characterized by abnormally elevated serum concentrations of thyroid-stimu- lating hormone (TSH) and normal serum concentrations of free thyroxine. 1,2 Subclinical hypothyroidism is caused by the same disorders of the thyroid gland as those that cause overt hypothyroidism. Among these are autoimmune thyroiditis, use of antithyroid drugs, hypothyroidism following thyroid ablation with 131 I, and hypothyroidism after thyroid excision. It is important to remember that abnormally elevated serum concentrations of TSH can occur as a transient phenomenon, particularly in patients receiving certain drugs such as lith- ium, amiodarone, sulpiride, metoclopramide, haloperidol, and spironolactone. 1 In contrast to overt hypothyroidism, which affects 1% to 4% of the population, the prevalence of subclinical hypo- thyroidism ranges from 5% to 10%. 3 It affects 6% to 10% of women (approaching 15% in women over 60 years of age) and 2.4% to 3% of men. 4 One of the most important pro- spective, population-based studies (Whickham Study) con- ducted in England has found abnormally elevated levels of TSH in 7.5% of female subjects and in 2.8% of male sub- jects. 5 The largest study to assess the prevalence of thyroid dysfunction demonstrated that in 25,862 study subjects, 11.7% showed abnormal TSH levels and, of these, 9% had subclinical hypothyroidism. 6 There is considerable controversy regarding the mor- bidity and the clinical significance of subclinical hypothy- roidism. 7,8 It can be a progressive condition, which leads to a series of metabolic consequences. Moreover, it is likely to be a risk factor for atherosclerosis and coronary disease. 9,10 In a cross-sectional cohort of middle-aged Dutch women, those with subclinical hypothyroidism were twice as likely to have atherosclerosis and a history of myocardial infarction as euthyroid control women. 10 On the other hand, in a 20-year follow up of the Whickham cohort, the rates of death of all causes and from cardiovascular causes were not significantly higher in subjects who had subclinical hypothyroidism. 11 The main question to be answered is whether individuals with subclinical hypothyroidism have only biochemical abnormal- ities that need to be monitored or if further laboratory inves- tigation and thyroid hormone replacement is required. The term itself (subclinical hypothyroidism) is questioned by several authors who suggest that subclinical hypothyroidism should be replaced by “slightly symptomatic hypothyroid- ism” or “minimal thyroid abnormality,” because these pa- tients can be symptomatic. 1 From the *Departamento de Medicina Interna, Setor de Endocrinologia, Hospital Universita ´rio Clementino Fraga Filho, Universidade Federal do Rio de Janeiro; †Nu ´cleo de Estudos de Sau ´de Coletiva, Universidade Federal do Rio de Janeiro; and ‡Servic ¸o de Patologia Clı ´nica, Labora- to ´rio de Hormo ˆnios, Hospital Universita ´rio Clementino Fraga Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil. Reprints: Monica Dias Cabral, MD, Av. das Ame ´ricas 1155, sala 1707, Barra da Tijuca – RJ – RJ, CEP: 22631– 000. E-mail: mdcabral@globo.com. Copyright © 2004 by Lippincott Williams & Wilkins ISSN: 1051-2144/04/1403-0121 DOI: 10.1097/01.ten.0000127928.08840.b7 The Endocrinologist • Volume 14, Number 3, June 2004 121