An Associative Investigation between Tsh and Serum Lipid Concentrations in the Population of Bhopal, India

The association between TSH and serum lipids in people with no apparent thyroid dysfunction is less understood. We have investigated the association between normal thyroid function, defined as TSH within the reference range and serum lipids concentrations. Cross-sectional, population based study with 1785 individuals without known thyroid dysfunction. We calculated mean concentrations of total serum cholesterol, low-density lipoprotein (LDL) cholesterol, non-high-density lipoprotein (HDL) cholesterol, HDL cholesterol and triglycerides across categories of TSH, using general linear models. Within the reference range of TSH, there was a linear and significant (P for trend <0.001) increase in total serum cholesterol, LDL cholesterol, non-HDL cholesterol and triglycerides, and linear decrease (P for trend <0.001) in HDL cholesterol with increasing TSH. Within the range of TSH that is considered clinically normal, we observed that increasing level of TSH was associated with less favorable lipid concentrations. The association with serum lipids was linear across the entire reference range of TSH. INTRODUCTION: A hormone produced by the pituitary gland at the base of the brain in response to signals from the hypothalamus gland in the brain. Thyroid stimulating hormone (TSH) promotes the growth of the thyroid gland in the neck and stimulates it to produce more thyroid hormones. When there is an excessive amount of thyroid hormones, the pituitary gland stops producing TSH, reducing thyroid hormone production. This mechanism maintains a relatively constant level of thyroid hormones circulating in the blood. TSH is a peptide hormone synthesized and secreted by thyrotrope cells in the anterior pituitary gland, which regulates the endocrine function of the thyroid gland. Hypothyroidism is a common endocrine disorder resulting from deficiency of thyroid hormone. It usually is a primary process in which the thyroid gland produces insufficient amounts of thyroid hormone. It can also be secondarythat is, lack of thyroid hormone secretion due to inadequate secretion of either thyrotropin (ie, thyroid-stimulating hormone [TSH]) from the pituitary gland or thyrotropin-releasing hormone (TRH) from the hypothalamus (secondary or tertiary hypothyroidism). The patient's presentation may vary from asymptomatic to, rarely, coma with multisystem organ failure (myxedema coma). The most common cause for hypothyroidism is autoimmune thyroid disease (Hashimoto thyroiditis). Subclinical hypothyroidism, also referred to as mild hypothyroidism, is defined as normal serum free T4 levels with slightly high serum TSH concentration, may also be associated with unfavourable serum lipids, especially if TSH is higher than 10mU/l . Further, thyroxine treatment of sub-clinically hypothyroid individuals may reduce total serum cholesterol and low