Thyroid gland is an important part of the endocrine system. It is a butterfly shaped gland situated in the neck. It synthesizes and releases an important hormone, thyroxine, which is essential for normal metabolism and functioning of every organ system in the body. In the fetus and during the first three years of life thyroxine is essential for normal brain development. During childhood, thyroxine is essential for normal growth and development. It plays a vital role in adolescents in helping them progress through puberty.
In pregnant mothers a normally functioning thyroid gland is essential to prevent/decrease complications like abortions, blood pressure in pregnancy and preterm delivery. In adults it is important for normal functioning of every organ system most importantly cardiovascular and neuromuscular systems.
The common endocrine diseases involving thyroid gland are hypothyroidism and hyperthyroidism where there is a decreased/absent or increased synthesis of thyroxine by the gland respectively. In a case of suspected hypothyroidism or hyperthyroidism the first investigation to be done is thyroid function tests which include estimation of TSH, Total T3 and Total T4 levels. Hypothyroidism is characterized by increased TSH and low T3 and T4 levels where as in hyperthyroidism TSH levels are low and T3, T4 levels are elevated.
Common symptoms associated with untreated hypothyroidism include swelling in front of neck, facial swelling, swelling of legs, constipation, poor height gain in children, subnormal intelligence, weight gain, menstrual irregularities in women, delay in development of puberty in boys and girls, lethargic behavior and muscle pains. Treatment includes thyroxine hormone supplementation. Common manifestations of thyrotoxicosis/hyperthyroidism include weight loss, increased sweating, increased frequency of stools or diarrhea, palpitations, anxious behavior and sometimes eye related symptoms like redness, protrusion of eyeballs, visual disturbances.
Thyrotoxic patients need workup to determine the cause of increased thyroid hormone levels, which can be due to Graves disease, toxic adenoma, toxic multinodular goiter or thyroiditis. This is possible with imaging techniques like technetium thyroid uptake scan or ultrasonography of neck and blood test to estimate TSH receptor antibodies (TRAb). Treatment options include medication with drugs which inhibit thyroid hormone synthesis, radioiodine therapy and rarely surgery.
Other conditions associated with thyroid gland include congenital hypothyroidism, thyroid nodules (malignant and benign) and thyroiditis. In congenital hypothyroidism, there is a defect at birth either in the development of thyroid gland or in synthesis of thyroxine hormone secondary to genetic cause. The incidence of congenital hypothyroidism is 1 in 4000 live births. It is essential to diagnose and treat this condition at the earliest to prevent mental retardation in children. This is possible by universal screening of newborns 72 hours after birth by estimating T3, T4 and TSH levels.
Swellings/ nodules occur quite commonly in thyroid gland. These can occur on a background of normal , hypo functioning or hyperfunctioning thyroid gland. While most swellings are benign in nature, few are due to underlying thyroid cancer. All thyroid nodules need proper evaluation by imaging via ultrasound followed by FNAC. The cancerous swellings are treated by surgical removal of the entire thyroid gland, whereas most benign swellings can be left alone unless they continue to enlarge during follow up or if they are large enough to compress surrounding structures in the neck. It is essential to note that, unlike other cancers, most thyroid cancers are curable with surgery leading to a normal life expectancy.
Thyroiditis is referred to as inflammation of the thyroid gland. It can be painful or painless. Because of increased leakage of thyroid hormones from an inflamed gland, patients may present with features of thyrotoxicosis and blood tests reveal a low TSH and increased T3, T4. Common presentations include pain/discomfort in front of neck with or without accompanying fever, ear pain, muscle pains and joint pains. It is a self-limiting condition and treatment is mainly symptomatic.
