Differential Diagnosis for Hyperactive Thyroid Function
- Single most likely diagnosis
- Toxic Multinodular Goiter (TMNG): This condition is characterized by the presence of multiple nodules in the thyroid gland, which can produce excess thyroid hormones, leading to hyperthyroidism. The high T4 and T3 levels, low TSH, and the presence of nodules on ultrasound (TI-RADS 4) with a recommendation for FNA biopsy, along with the absence of Graves' antibodies, support this diagnosis. TMNG is a common cause of hyperthyroidism in older adults and can present with a variety of symptoms, including weight loss, palpitations, and anxiety.
- Other Likely diagnoses
- Toxic Adenoma: A solitary thyroid nodule that produces thyroid hormones independently of the normal pituitary-thyroid axis, leading to hyperthyroidism. While the presence of multiple nodules (TI-RADS 4) might suggest TMNG, the possibility of a dominant toxic adenoma cannot be ruled out without further evaluation.
- Thyroiditis (Subacute or Silent): Although less likely given the ultrasound findings and the absence of symptoms typically associated with thyroiditis (such as pain or tenderness), it remains a consideration. However, thyroiditis usually presents with a painful thyroid gland and can have a phase of hyperthyroidism due to the release of pre-formed thyroid hormones.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Medullary Thyroid Carcinoma: Although rare, this type of thyroid cancer can produce excess thyroid hormones and should be considered, especially if the FNA biopsy is suggestive or if there's a family history of medullary thyroid carcinoma.
- Anaplastic Thyroid Cancer: A very aggressive form of thyroid cancer that can cause rapid growth and destruction of the thyroid gland, potentially leading to hyperthyroidism. Early diagnosis is crucial but often challenging due to its rapid progression and non-specific symptoms.
- Rare diagnoses
- Struma Ovarii: A rare ovarian tumor that contains thyroid tissue, which can produce thyroid hormones, leading to hyperthyroidism. This diagnosis would be considered if other evaluations are inconclusive and there's evidence of an ovarian mass.
- Familial Non-Autoimmune Hyperthyroidism: Rare genetic conditions that lead to hyperthyroidism without autoimmune antibodies. These conditions are typically identified through genetic testing and family history.