The thyroid is a large endocrine gland situated at the base of the neck. The gland consists of a large number of closed follicles inside which are a jelly like substance, which contains thyroglobulin, and the main active substances that are secreted by the gland.


The thyroid gland regulates metabolic rate through the secretion of thyroid, which is stimulated by thyroid-stimulating hormone from the pituitary gland.


The C-cells of the thyroid secrete calcitonin (a hormone that lowers the levels of calcium and phosphate in the blood)
Thyroid hormone is an iodine containing substance. It’s essential for normal metabolic processes and mental and physical development. There are two thyroid hormones made from thyroglobulin.


Lack of thyroid hormones gives rise to:


  • Cretinism in infants that leads to mental retardation
  • Myxoedema in adults. The symptoms in adults are a slow down both mentally and physically, undue sensitivity to cold, weight gain and coarsening of the skin.

Excessive production gives rise to:


  • Thyrotoxicisis which gives rise to rapid heart rate, sweating, tremor, increased appetite, loss of weight and intolerance of heat.

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