The Thyroid

What is the Thyroid?

In this section, a brief introduction is provided to facilitate an understanding of the Thyroid and its role in the human body.

Thyroid Structure

The thyroid gland is a butterfly-shaped organ located in the base of the neck consisting of right and left lobes each measuring about 4 x 2 cm connected by a bridge called isthmus. The normal thyroid gland is barely palpable within the neck. An enlargement of the gland involving the whole gland is termed goiter. An enlarged thyroid gland involving both lobes is called a diffuse goiter. A discreet enlargement of any portion of the gland is called a nodule, which may be single or multiple.

The most common cause of thyroid gland enlargement is iodine deficiency. A thyroid nodule whose content is fluid may be due to a thyroid cyst or to a bleeding; a solid nodule may be benign or malignant.

Thyroid Function

The optimal function of the thyroid gland is essential for normal growth and development of man. The thyroid gland produces two hormones called thyroxine (or T4) and triiodothyronine (or T3) which are synthesized from iodine taken up from food.

The thyroid produces its hormones in normal quantities unless affected by disease. It may then have either an excessive or deficient production called hyperthyroidism or hypothyroidism, respectively. The symptoms are contrasting with one another: on one hand, excessive production causes weight loss, palpitations, intolerance to heat & sweating, frequent bowel movements and tremors; while, on the other hand, deficient production leads to weight gain, cold intolerance, constipation, tiredness and sleepiness.

Thyroid system
Image from Wikimedia Commons