Endocrine Abstracts (2001) 2 P17

High uptake of I123-Tyr3 Octreotide in the thyroid gland- the significance of hot thyroid nodules in screening for carcinoid metastases

K Kos1, A Lakhdar1 & J Hill2

1Departement of Medicine and Endocrinology, Royal preston Hospital, Preston, UK; 2Department of Nuclear Medicine, Royal Preston Hospital, Preston, UK.

A previously fit 36 year old lady presented with 3 days of pleuritic chest pain and SOB. A CxR showed consolidation at the left heart border. Following antibiotics she made a good recovery. On examination an incidental right thyroid nodule was identified. She was clinically euthyroid. FT4,FT3 were normal and TSH suppressed. The CxR a month later did not change. A CT scan revealed a 5x4cm mass in the left lower lobe, abutting the descending aorta and left atrium. Bronchoscopy revealed only left bronchus narrowing. Our differential diagnosis was pulmunary sequestration or unusual tumour. Open thoracotomy frozen sections unveiled bronchial carcinoid, which led to left pneumonectomy. Post operatively 5HIAA was normal.

Thyroid follow up a month after presentation revealed clinical euthyroidism with normal FT4, a FT3 of 6.8 (normal range 3-6.5) and suppressed TSH. An isotope technetium scan revealed enlargement of the right lobe, replaced by a hot nodule and suppressed remaining gland in keeping with Plummer's disease. Two FNA's showed no evidence of malignancy. Screnning for carcinoid metastasis one month post operatively by an I123-Tyr3 Octreotide scan showed insignificant tracer uptake at the pneumonectomy site and strong uptake at the indicated right thyroid nodule suspicious of medullary thyroid carcinoma or carcinoid metastases. Histology after surgical removal confirmed a benign thyroid adenoma.

The sensitivity of I123-Tyr3 Octrotide scans visualising extrahepatic carcinoid lesions is at least 60% and independent of urinary 5HIAA in previous studies. Octreotide scans are said to identify 71% of medullary thyroid carcinomas. High thyroid uptake is also described in untreated hyperthyroidism and Graves' disease thought due to local inflammation. There is no data on the behaviour of OCTA scans in multinodular goitres ot hot nodules. Our case demonstrates that interpretation of Octreotide uptake in the thyroid in the screening for carcinoid metastases warrants a wider differential.

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