A 30-year-old woman comes to the clinic reporting anxiety, weight loss of about 6 kgs and a feeling of "nervousness" in the last three months. Physical examination showed tachycardia, hyperreflexia and absence of goiter. TSH values are < 0.01 microU/mL, T4 is elevated and thyroglobulin levels are decreased. A scan reveals an absence of uptake in the thyroid region. What seems to you the most likely diagnosis?
Patients with this disorder voluntarily or accidentally ingest excessive amounts of thyroid hormone, resulting in hyperthyroidism in the absence of goiter. In contrast to all other causes of hyperthyroidism, serum thyroglobulin is not elevated and is almost always low or at the lower limit of normal. The fundamental doubt we had with ovarian teratoma (ovarian struma) which is a rare variant of mature monodermal teratoma composed of thyroid tissue described at the beginning of the 20th century. It is so named when the teratoma is predominantly composed of mature thyroid tissue (at least 50%, in order to be classified as struma ovarii). It represents between 2.5 and 5% of ovarian teratomas. In itself, it is a benign tumor, but in up to 5% of cases it can develop a malignant transformation of its elements, classically referred to as malignant struma ovarii. Mostly, the neoplastic tissue developed is a papillary carcinoma, less frequently it corresponds to follicular carcinoma. This malignant transformation arises mostly from classical forms of struma, but is extremely rare in cases of mature cystic teratomas. Its behavior is similar to that of other primary ovarian tumors, tending to metastasize to the peritoneal cavity and hematogenously to bone, liver and brain. The mean age of presentation of thyroid carcinoma on struma ovarii is between 42.9-44 years and between 21 and 63 for the papillary carcinoma variant. Clinically, the predominant form of presentation is as a pelvic mass or abdominal pain (45%), less frequently hyperthyroidism (5-8%) or ascites (17%). It is postulated that the ovarian thyroid tissue in the struma is autonomous in the production of thyroid hormones, so it is essential to measure serum thyroglobulin levels in patients affected by hyperthyroidism, as they point to the extrathyroid production of thyroid hormone.
Factitious thyrotoxicosis.
Hyperthyroidism due to Graves' disease.
Ovarian teratoma (ovarian stromal).
Subacute thyroiditis.