Write a short note on the disorders/diseases of the thyroid gland.

(N/A) The thyroid gland is located on either side of the trachea and consists of two lobes interconnected by a thin flap of connective tissue called the isthmus. It is composed of follicles and stromal tissues. The follicular cells synthesize two hormones: tetraiodothyronine or thyroxine $(T_4)$ and triiodothyronine $(T_3)$. Iodine is essential for the normal rate of hormone synthesis.
$1$. Hypothyroidism: Deficiency of iodine in our diet leads to hypothyroidism and enlargement of the thyroid gland,commonly called goitre. Symptoms include stunted growth (cretinism),mental retardation,low intelligence quotient,abnormal skin,and deaf-mutism. Hypothyroidism during pregnancy causes defective development and maturation of the growing baby. In adult women,it may cause irregular menstrual cycles.
$2$. Hyperthyroidism: This condition occurs due to cancer of the thyroid gland or the development of nodules,which increases the synthesis and secretion of thyroid hormones to abnormally high levels,adversely affecting body physiology.
$3$. Graves' Disease (Exophthalmic Goitre): This is a form of hyperthyroidism characterized by the enlargement of the thyroid gland,protrusion of the eyeballs,increased basal metabolic rate,and weight loss.