Thyroid lobe

The thyroid gland has two main sections - the right lobe and the left lobe. Each is roughly cone-shaped and nestles against the side of the trachea (windpipe), connected across the front by the isthmus.

Occasionally a third, thin upward extension called the pyramidal lobe is present - a remnant from the thyroid's development in early life. Its presence is a normal anatomical variant.

Each lobe is packed with tiny follicles: fluid-filled sacs lined with thyroid cells where T4 and T3 are made and stored. When the pituitary gland signals that more hormone is needed, the follicles release it into the bloodstream.

In thyroid surgery, a surgeon may remove just one lobe (hemithyroidectomy) or only the isthmus (isthmusectomy), depending on where a nodule or concern is located - making the anatomy of the lobes clinically important.