Question

What is a common cause of primary hypothyroidism?

Answer 1

A shortage of Iodine in the diet.

Explanation:

The Thyroid gland produces Thyroid hormones: TetraIodoThyronine, also known as `T_4` and TriIodoThyronine or `T_3`. Hypothyroidism means thyroid is under active, and produces insufficient amounts of thyroxine. (It also produces the hormone Calcitonin, by the way)

Formulae:

T3: (Tri-Iodo-Thyronine)

T4: (Tetra-Iodo-Thyronine)

T3 is actually the more potent of the two....

Both these hormones are produced in the Thyroid gland by the conversion of ThyroGlobulin. This is done by combining its Tyrosine residues (side chains) with Iodine.

If there's not enough Iodine available to the body, then not enough T3 and T4 can be produced...