Differential Diagnosis for Elevated Free T4 and T3
Single Most Likely Diagnosis
- Hyperthyroidism due to Graves' Disease: This is the most common cause of elevated free T4 and T3 levels, characterized by an autoimmune stimulation of the thyroid gland, leading to excessive production of thyroid hormones.
Other Likely Diagnoses
- Toxic Multinodular Goiter: A condition where multiple nodules in the thyroid gland become overactive, producing excess thyroid hormones.
- Thyroiditis: Inflammation of the thyroid gland, which can cause the release of stored thyroid hormones into the bloodstream, leading to elevated levels.
- Exogenous Thyroid Hormone Ingestion: Accidental or intentional ingestion of excessive amounts of thyroid hormone medication can cause elevated free T4 and T3 levels.
Do Not Miss Diagnoses
- Thyroid Storm: A life-threatening complication of untreated or undertreated hyperthyroidism, characterized by extreme elevations in thyroid hormone levels, which can lead to cardiac arrest, stroke, or multi-organ failure if not promptly recognized and treated.
- Pituitary Tumor (TSH-producing Adenoma): A rare tumor of the pituitary gland that secretes thyroid-stimulating hormone (TSH), leading to hyperthyroidism due to the stimulation of the thyroid gland.
Rare Diagnoses
- Struma Ovarii: A rare ovarian tumor that contains thyroid tissue, which can produce thyroid hormones, leading to hyperthyroidism.
- Familial Non-Autoimmune Hyperthyroidism: A rare genetic condition that affects the regulation of thyroid hormone production, leading to hyperthyroidism.
- Iodine Induced Hyperthyroidism (Jod-Basedow Phenomenon): A rare condition where excessive iodine intake leads to hyperthyroidism, particularly in individuals with pre-existing thyroid conditions.