Hyperthyroidism happens when the thyroid gland makes too much thyroid hormone. This condition is also called overactive thyroid. Hyperthyroidism speeds up the body's metabolism and leads to a high BMR (basal metabolic rate). That can cause many symptoms, such as weight loss, hand tremors, and a rapid or irregular increase in heartbeat.
A deficiency of iodine in our diet results in hypothyroidism. It causes defective development and maturation of the growing baby, leading to stunted growth (cretinism), mental retardation, oedema, obesity, and a lack of alertness. In adult women, hypothyroidism may cause the menstrual cycle to become irregular.