Thyroid lobe

Lobus glandulae thyroideae

Endocrine & glandsGlandsNeckLeft and right

View left in 3D View right in 3D

What it is

One of the two lobes of the butterfly-shaped thyroid, lying against the side of the windpipe just below the voice box. Its pointed upper pole rests on the thyroid cartilage and its rounded lower pole reaches the 5th–6th tracheal ring. It is packed with hormone-filled follicles.

Function

Makes thyroxine (T4) and triiodothyronine (T3), which set the metabolic rate of nearly every cell, plus calcitonin from its C cells, which lowers blood calcium.

Size

Each lobe about 5 × 2.5 × 2 cm; whole gland 15–25 g

Clinical note

The gland is bound to the larynx by fascia, so a thyroid lump moves up and down when the patient swallows — the classic bedside test. Enlargement (goitre) is usually due to iodine deficiency worldwide.