Differential Diagnosis
- Single most likely diagnosis
- Immune-mediated activation of TSH receptors: This is the most likely diagnosis, given the patient's symptoms of hyperthyroidism (weight loss, palpitations, heat intolerance), exophthalmos, and the presence of a diffuse goitre with a bruit. The laboratory results also support this diagnosis, with low TSH and elevated free T4 and T3 levels. This presentation is consistent with Graves' disease, an autoimmune disorder that causes hyperthyroidism due to immune-mediated activation of TSH receptors.
- Other Likely diagnoses
- Autonomous hyperfunctioning nodules: Although less likely, this diagnosis could also explain the patient's hyperthyroidism. However, the presence of a diffuse goitre and exophthalmos makes Graves' disease more likely.
- Activating germline mutations in TSH receptor genes: This is a rare cause of hyperthyroidism, but it could be considered in the differential diagnosis, especially if there is a family history of the condition.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Thyroid gland inflammation causing release of preformed thyroid hormones: This condition, known as thyroid storm, is a life-threatening complication of hyperthyroidism. Although the patient's symptoms do not currently suggest thyroid storm, it is essential to monitor her closely and be aware of the potential for this condition to develop.
- Rare diagnoses
- Overexpression of thyroid peroxidase leading to enhanced thyroid hormone synthesis: This is a rare cause of hyperthyroidism and is not typically associated with the patient's symptoms or laboratory results.
- Other rare causes of hyperthyroidism, such as struma ovarii or metastatic thyroid cancer, are unlikely given the patient's presentation and laboratory results. However, they should be considered if the patient's condition does not respond to treatment or if additional symptoms develop.