MEASUREMENT OF SERUM TSH IN THE INVESTIGATION OF PATIENTS PRESENTING WITH THYROID ENLARGEMENT

In otherwise euthyroid patients presenting with thyroid enlargement, r eduction in serum thyrotrophin (TSH) concentrations measured in a sens itive assay may be a marker of thyroid autonomy and may therefore indi cate a benign underlying pathology. We investigated prospectively a co hort of 467 subjects presenting consecutively to our thyroid clinic wi th nodular or diffuse enlargement of the thyroid. Subjects were divide d into those cvi ih normal (0.4-5.5 mU/l), low but detectable (0.1-0.3 9 mU/l) or undetectable (<0.1 mU/l) serum TSH concentrations. The fina l pathological diagnosis was defined by fine-needle aspiration cytolog y;and clinical follow-up of at least 2 years or by fine-needle aspirat ion cytology and histology following surgical treatment. Serum TSH con centrations below normal were found in 75 patients (16.1%), those with low serum TSH results having higher mean free T4 concentrations, were older and were more likely to be female. In those with undetectable s erum TSH, no patient had a diagnosis of thyroid neoplasia and in those with low but detectable TSH, thyroid neoplasms were diagnosed in two patients (3.4%). In those with normal serum TSH, 12.0% had a final dia gnosis of thyroid neoplasm (p=0.013). Overall, thyroid malignancy was found in one patient (1.3%) of those with a serum TSH measurement belo w the normal range and 6.9% of those with normal serum TSH (p<0.06). R eduction in serum TSH at presentation may identify a group which requi res less intensive investigation and follow-up than those without bioc hemical evidence of thyroid autonomy.