SYNOPSIS: In a rare case of thyrotoxicosis, transitioning in less than a month post-thyroidectomy from subclinical hyperthyroidism into frank hyperthyroidism, active thyroid hormone production was documented as coming from a metastatic focus in the occiput of the patient.CLINICAL PRESENTATION: A 63-year-old Filipino woman came in for a 4-year-duration left occipital mass measuring 9 cm x 8 cm, along with thyroid nodules which were 3-cm in the right lobe and 2-cm in the left lobe. Suspected to have metastatic thyroid carcinoma, she underwent total thyroidectomy. From a pre-operative subclinical hyperthyroid state, she developed overt symptoms and signs of thyrotoxicosis within one month post-operatively.PHYSICAL FINDINGS: One month post-thyroidectomy, the patient lost 5 percent of immediate post-op weight, was ambulatory, with a heart rate of 118 beats/min. Skin was warm and moist. On her left occiput was a 9 cm x 8 cm superficial mass. A 10-cm horizontal scar was seen on the anterior base of the neck, with no masses. There were fine finger tremors and + + + deep tendon reflexes.LABORATORY WORK-UP: Thyroid FNAB was suspicious for follicular tumor. Total thyroidectomy specimen showed follicular carcinoma, widely invasive, right and left lobes. Whole body 1-131 scintigraphy revealed functioning metastatic thyroid tissue in the head, corresponding to the palpated mass. Head CT scan revealed occipital calvarial metastasis with intracranial/ extradural extensions. From a pre-operative subclinical hyperthyroid state (FT4=22.2 pmol/L [NV 12-24 pmol/L], TSH=0.07 mm/L [NV 0.4-4 mIU/L]), patient became frankly hyperthyroid 1 month post-op (FT4=49.4 pmol/L, FT3= 30.4 pmol/L, TSH=0.06 mlU/L).Diagnosis: Follicular Thyroid Carcinoma Stage IVC S/P Total Thyroidectomy; Thyrotoxicosis (T4 type) secondary to Hyperfunctioning Occipital Bone Metastasis.TREATMENT/OUTCOME: The patient was given carbimazole and propranolol with resolution of thyrotoxic signs and symptoms. Still of good functional capacity, she now awaits palliative external beam radiotherapy and subsequent radioiodine therapy.SIGNIFICANCE: This is one of the less than 100 reported cases around the world, of thyrotoxicosis caused by hyperfunctioning thyroid carcinoma, since the first reported case in 1948.
Thyroid Cancer ; Thyrotoxicosis ; Metastatic Follicular Thyroid Carcinoma