Endocrine Abstracts

We present a case of 40 years old lady who was referred to us with a thyroid nodule in her right lobe. She was well, but on specific questioning reported weight loss of about 3 kgs over the past month and some mild heat intolerance. The nodule was 2 cm in size and the patient was clinically euthyroid. Thyroid function tests demonstrated a suppressed serum TSH with a mildly elevated serum T3. A thyroid ultrasound scan was performed which demonstrated that the palpable nodule was located in the upper pole of the right lobe of thyroid, and this nodule was hyperfunctioning or "hot". There was less than a 1% chance that nodule was malignant and fine needle aspiration biopsy (FNAB) is not indicated. Uptake throughout the remainder of the thyroid was relatively suppressed. The patient had an autonomous functioning thyroid nodule and was referred for radioiodine therapy.

Discussion: Thyroid nodules are very common with 50% of people over fifty years having thyroid nodules on ultrasound. The great majority of these nodules are not malignant. Thyroid nodules under 1 cm in size do not need to be investigated with thyroid scans, ultrasounds, blood tests or FNAB. There is a very low chance that such nodules are malignant and these can be watched clinically to detect if the nodule is growing. Physical exam findings that increase the concern for malignancy include: Nodules larger than 4 cm in size, firmness to palpation, fixation of the nodule to adjacent tissues, cervical lymphadenopathy, and vocal fold immobility. Provided that the patient is not thyrotoxic, the best investigation of a thyroid nodule is a FNAB. In this setting, most thyroid nodules are hypofunctioning or “cold” on thyroid scans and there are no ultrasound findings that can exclude malignancy. Prior to ultrasound guided FNAB, the size of the nodule can be measured accurately which may help in future management of the patient. Despite a sensitivity of 65-98% and a specificity of 72-100% for thyroid cancer, unfortunately, FNAB biopsies are far from perfect with about 20% of FNAB’s being non diagnostic and may miss malignant nodules in up to 5% of patients.

Conclusion: In the euthyroid patient, FNAB is the best investigation for patients with nodules greater that 1 cm in size. Nodules less than this size can be left for surveillance in primary care.