Thyroid Disorders and Anatomy

What is the typical location of the isthmus of the thyroid gland?

What is the average weight of a normal thyroid gland?

What is the function of calcitonin produced by the thyroid gland?

What is the importance of recognizing the intimate relationship between the thyroid gland and the recurrent laryngeal nerve?

What is the typical shape of each thyroid lobe?

What is the name of the superior extension of the thyroid gland that is present in up to 70% of cases?

What is the significance of a palpable thyroid gland?

What are the principal thyroid hormones produced by the thyroid gland?

What is the typical location of the parathyroid glands in relation to the thyroid gland?

What is the precursor to the synthesis of thyroid hormones?

Thyroid Disorders

Thyroid disorders are common and can present with a neck swelling or symptoms and signs of thyroid dysfunction (hypo- or hyper-thyroidism).

Thyroid Anatomy

The thyroid gland consists of two lateral lobes joined by the isthmus, which overlies the 2nd and 3rd tracheal rings.
The pyramidal lobe is a superior extension near the midline, present in up to 70% of cases.
Each thyroid lobe is cone-shaped, measuring approximately 5cm in length and 2-3 cm wide in its transverse and anteroposterior dimensions.
The thyroid gland weighs 15-25g.
A normal thyroid gland is not palpable, and a visible or palpable thyroid almost always implies some degree of enlargement and pathology.

Thyroid Physiology

The thyroid gland produces thyroid hormones, primarily triiodothyronine (T3) and thyroxine (T4), which regulate growth and function of many organ systems.
T3 and T4 are synthesized from iodine and tyrosine.
The thyroid also produces calcitonin, which plays a role in calcium homeostasis.
Thyroid hormone output is regulated by thyroid-stimulating hormone (TSH) produced by the anterior pituitary, which is regulated by thyrotropin-releasing hormone (TRH) produced by the hypothalamus.

Thyroid Enlargement

Thyroid enlargement can be symmetric (goitre) or asymmetric (solitary nodule).
A thyroid enlargement can be differentiated from other causes of a cervical mass by its location in the lower midline of the neck and its movement on swallowing.

Identify and manage thyroid disorders, including thyroid swelling and dysfunction. Learn to differentiate thyroid swelling from other neck masses and recognize symptoms of hypo- and hyperthyroidism.