Hyperthyroidism can be caused by Graves' disease, thyroid nodules, thyroiditis, or consuming too much iodine. Which statement is NOT a common cause?

• A. Graves' disease
• B. Thyroid nodules
• C. Thyroiditis
• D. Vitamin D deficiency

Answer: (D)

Hyperthyroidism comes from conditions that increase thyroid hormone production or release. Graves’ disease is an autoimmune process where antibodies stimulate the TSH receptor, driving excess thyroid hormone. Thyroid nodules, such as a toxic adenoma or toxic multinodular goiter, can autonomously secrete hormone. Thyroiditis involves inflammation of the thyroid and can cause the release of stored thyroid hormone during the acute phase, leading to temporary hyperthyroidism. Consuming too much iodine can also spark hyperthyroidism in some individuals, known as the iodine-induced or Jod-Basedow effect.

Vitamin D deficiency, however, does not have a mechanism that increases thyroid hormone production or release. It primarily affects bone health and calcium metabolism, not thyroid function. Therefore it is not a common cause of hyperthyroidism.