Prevalence of hypercholesterolemia in hypothyroidism compared with euthyroid controls: effects of levothyroxin replacement therapy

Background: Hypothyroidism (HT), a relatively common condition among general population is associated with lipid profile abnormalities. The present study was designed to determine the contributive role of HT in the development of hypercholesterolemia (HCH). Methods: One hundred thirty six consecutive patients with HT and 272 euthyroid controls entered the study. Serum total cholesterol (CH) level was determined before and after treatment of HT and compared with controls. Frequency of subjects with HCH defined as plasma total CH level > 240 mg/dl, were determined and compared between hypothyroid patients and sex - age-matched controls. The contributive role of HT in the development of HCH was determined by the comparison of pre and post-treatment CH levels. HT-induced HCH was regarded as restoration of HCh (reduction of CH level to less than 240 (mg/d) after achievement of euthyroid state with thyroid hormone. Results: The mean ages of patients and controls was 43±13 and 44±13 years, respectively. In HT patients the frequency of HCH and mean level of Ch were significantly higher compared with sex and age-matched euthyroid controls. Replacement therapy of 44 HT patients resulted to a significant reduction of CH level from baseline by 22% (p < 0.0001) in the whole number of patients, and reduction of 32.2% (p < 0.0001) along with restoration of HCH in 22(50%) patients. Whereas, in 22 patients after achievement of euthyroid state, despite a significant reduction of Ch from baseline (12%, p < 0.05), HCH persisted and CH levels remained > 240mg/dl. Conclusion: The results show contributive role for HT in the development of HCH. Two different populations of HCH with different responses to replacement therapy is recognizable in HT.