Diet and Thyroid Disease

Abstract

The prevalence of thyroid disorders is increasing day by day. The thyroid is the butterfly gland located at the neck region which produces two hormones, thyroxine (T4) and triiodothyronine (T3). These hormones regulate the metabolic functions of the cells. The thyroid regulating hormone (TRH) and thyroid stimulating hormone (TSH) regulates the level of T3 and T4. The reduced level of TSH is an indication of hyperthyroidism and the increased level of TSH leads to hypothyroidism. Although in most cases these hormonal disorders are non-curable, this short review suggests a diet plan to alleviate the symptoms associated with the ailment. The thyroid gland makes two hormones, thyroxine (T4) and triiodothyronine (T3). The former is a prohormone and the latter is an active hormone [1]. The deiodination of T4 by the 5'deiodi-nase (5'D) enzyme, which removes a iodine molecule from T4 to form T3 or rT3 in liver and kidney releases major proportion of T3 and about 20% of T3 is secreted in thyroid gland itself. These hormones perform same function but differ in speed and intensity of action [2]. T3, although present in lesser amount in blood stream, is more active than T4 [3]. The level of T3 and T4 is regulated by hypothalamus and hypophysis in brain. The hypothalamus produces thyroid regulating hormone (TRH) which regulates the production of thyroid stimulating hormone (TSH) by hypophysis. TSH controls thyroid gland to produce T3 and T4. T3 negatively regulates hypophys and T4 negatively affects hypothalamus [3]. The major function of thyroid hormones (THs) is to control the metabolism of fat and carbohydrate by the body cells. In addition, they have significant role in respiration, heart and nervous system, maintaining the body temperature, blood calcium levels, menstrual cycles, and skin integrity, brain development. THs also control cholesterol levels by regulating the cholesterol synthesis, cholesterol receptors, and the rate of cholesterol degradation [4]. Low levels of THs lead to a higher blood lipid profile, increased blood pressure, and elevated levels of the amino acid homocysteine and the inflam-matory marker C-reactive protein. Thyroid disorders have a link with impaired glucose control, and diabetes [4]. The Thyroid hormones and disorders Thyroid disorders affects about 10-15% of the population [2]. Around 20% suffers from temporary or permanent thyroid disorder. Majority of population affected with either hypothyroidism or hyperthyroidism. Hypothyroidism is a complication associated with the autoimmune disorder, Hashimoto's disease. Low levels of thyroid hormones T3 and T4 leads to slow down in thyroid controlled functions of the body. The symptoms are described in table 1. Hyperthyroidism (Table 2) on the other hand is a consequence of overproduction of thyroid hormones. It is usually related to autoimmune Grave's disease. Another category of thyroid dys-function is subclinical hypothyroidism in which T3 and T4 levels are normal but with high TSH concentration with or without non-specific symptoms. To be specific TSH raised above 5-6 mU/L is considered as abnormal condition. It generally affects women than men and is directly proportional to age of the individual [5].