How can the thyroid gland change in size?

The thyroid gland can change in size due to several physiological and pathological factors, a condition commonly referred to as a goitre.

The primary mechanisms for this enlargement include:

• Hormonal Stimulation: When thyroid hormone production is low—often due to iodine deficiency or defects in hormone synthesis—the pituitary gland secretes excess thyrotropin. This hormone stimulates the growth of thyroid cells in an attempt to restore normal hormone levels.12
• Autoimmune Activity: In conditions like Graves disease, the body produces antibodies that bind to and activate thyrotropin receptors, mimicking the stimulatory effect of thyrotropin and causing the gland to enlarge.13
• Nodule Formation: The development of one or more benign or malignant thyroid tumours (adenomas or carcinomas) can cause localized swelling or an increase in the overall size of the gland.14
• Inflammation: Thyroiditis, which involves the infiltration of the gland by lymphocytes or other inflammatory cells, can also lead to enlargement.13