Charles M. Intenzo MD, Presenter: Nothing to Disclose

Jeffrey Miller MD, Abstract Co-Author: Nothing to Disclose

Serge Jabbour MD, Abstract Co-Author: Nothing to Disclose

Sung M. Kim MD, Abstract Co-Author: Nothing to Disclose

David Capuzzi MD, Abstract Co-Author: Nothing to Disclose

Subclinical hyperthyroidism (SBH) is defined as suppression of thyroid stimulating hormone (TSH) levels with normal serum hormone (T3 and T4) levels.  SBH often progresses to overt hyperthyroidism.  Our aim is to (1) classify the thyroid scan findings of SBH according to the etiology of the underlying thyroid disorder, and (2) determine the frequency with which patients with SBH become thyrotoxic. 

Over a 7-year period, a total of 86 patients with SBH underwent thyroid scintigraphy. Follow-up was obtained by contacting the referring physician or by review of medical records, or in some cases there were follow-up thyroid scans.

(1) 51 of the 86 patients (58.3%) with SBH had a autonomously functioning thyroid nodule(AFTN), 29 of whom developed toxic autonomous nodules (TAN), 10 remained euthyroid, and 12 were lost to follow-up.  (2) 24 patients (27.9%) had a multinodular goiter (MNG), 9 of whom progressed to a toxic MNG, while 7 remainded euthyroid, and 8 were lost to follow-up.  (3) 7 patients (8.1%) demonstrated diffuse gland enlargement and were termed "evolving Graves' disease".  6 of these patients developed overt Graves' disease, and 1 was lost to follow-up.  (4) 4 patients (4.7%) had very low radioiodine uptake with decreased tracer activity, presumably from resolving silent thyroiditis. 

(1) AFTN was the most common etiology of SBH, and most progressed to a toxic adenoma.  (2) All paients with evolving Graves' disease became thyrotoxic.

Autonomous thyroid nodule is the etiology of most cases of subclinical hyperthyroidism, and often become toxic. 

Intenzo, C, Miller, J, Jabbour, S, Kim, S, Capuzzi, D, The Scintigraphic Presentation and Clinical Outcomes of Subclinical Hyperthyroidism.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6010885.html