Thyroid hormone is essential for normaldevelopment, differentiation, and metabolic balance (1). Hypothyroidismis a common endocrine disorder affecting1.4% to 2.
0% of women and 0.1% to 0.2% of men. Typical symptoms are consistent withdeclining metabolic functions and range from vague complaints of fatigue insubclinical deficiency to overt clinical symptoms involving changes inmentation and memory, lethargy, weight gain, cold intolerance, constipation,and goitre enlargement of the thyroid gland.
Themost common cause of hypothyroidism is destruction of the thyroid gland bydisease or as a consequence of attempts of various therapies to controlthyrotoxicosis. Primary hypothyroidism may also result from inefficient hormonesynthesis caused by inherited defective production, a deficient supply ofiodine or inhibition of hormonogenesis by various drugs and chemicals. In suchinstances, hypothyroidism is typically associated with thyroid gland enlargement.Themental picture in patients with overt hypothyroidism usually is one of extremecomplacency. Memory is undoubtedly impaired, and attention and the desire tothink are reduced. The emotional level seems definitely low, and irritabilityis decreased. Except in the terminal stage, reasoning power is preserved.
In aminority of patients, nervousness and apprehension are present. Cognitive testsof patients with moderate to severe hypothyroidism indicate difficulties inperforming calculations, recent memory loss, reduced attention span, and slowreaction time. Atypicalpresentations such as weight loss, hearing impairment, tinnitus, and carpaltunnel syndrome may occur, especially in the elderly (2, 3). Hypothyroidism may occur as a result of radioiodineor surgical treatment for hyperthyroidism, thyroid cancer, or benign nodularthyroid disease and after external beam radiation for non-thyroid-related headand neck malignancies, including lymphoma (4).