The Role of Nuclear Medicine in the Clinical Management of Benign Thyroid Disorders. Part 2. Nodular Goiter, Hypothyroidism, and Subacute Thyroiditis

Abstract

Learning Objectives: On successful completion of this activity, participants should be able to have acquired knowledge on (1) the clinical manifestations, underlying pathophysiology, imaging modalities, and therapy of non-toxic nodular goiter; (2) the clinical manifestations, underlying pathophysiology, imaging modalities, and therapy of hypothyroidism; and (3) on the clinical manifestations, underlying pathophysiology, imaging modalities, and therapy of subacute thyroiditis.Financial Disclosure: The authors of this article have indicated no relevant relationships that could be perceived as a real or apparent conflict of interest.CME Credit: SNMMI is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to sponsor continuing education for physicians. SNMMI designates each JNM continuing education article for a maximum of 2.0 AMA PRA Category 1 Credits. Physicians should claim only credit commensurate with the extent of their participation in the activity. For CE credit, SAM, and other credit types, participants can access this activity through the SNMMI website (http://www. snmmilearningcenter.org) through July 2024.Part 2 of this series of Continuing Education articles on benign thyroid disorders deals with nodular goiter, hypothyroidism, and subacute thyroiditis. Together with Part 1 (which dealt with various forms of hyperthyroidism), this article is intended to provide relevant information for specialists in nuclear medicine dealing with the clinical management of patients with benign thyroid disorders, the primary audience for this series. Goiter, an enlargement of the thyroid gland, is a common endocrine abnormality. Constitutional factors, genetic abnormalities, or dietary and environmental factors may contribute to the development of nodular goiter. Most patients with nontoxic nodular goiter are asymptomatic or have only mild mechanical symptoms (globus pharyngis). Workup of these patients includes measurement of thyroid-stimulating hormone, free triiodothyronine, free thyroxine, thyroid autoantibodies, ultrasound imaging, thyroid scintigraphy, and fine-needle aspiration biopsy of nodules with certain ultrasound and scintigraphic features. Treatment for multinodular goiter includes dietary iodine supplementation, surgery, radioiodine therapy (to decrease thyroid size), and minimally invasive ablation techniques. Hypothyroidism ranges from rare cases of myxedema to more common mild forms (subclinical hypothyroidism). Primary hypothyroidism often has an autoimmune etiology. Clinical presentations differ in neonates, children, adults, and elderly patients. Work-up includes thyroid function tests and ultrasound imaging. Nuclear medicine is primarily used to locate ectopic thyroid tissue in congenital hypothyroidism or to detect defects in iodine organification with the perchlorate discharge test. Treatment consists of thyroid replacement therapy with L-thyroxine, adjusting the daily dose to the individual patient's metabolic and hormonal requirements. Subacute thyroiditis is a selfl...

Subacute Thyroiditis—Still a Diagnostic Challenge: Data from an Observational Study

“…Since SAT symptoms are not always specific, a diagnostic delay has been reported [ 8 , 16 ]. Nuclear scintigraphy in the initial stage of the disease reveals a characteristic absent radioisotope uptake (due to the release of preformed hormones from the damaged thyroid gland and TSH suppression), which confirms the diagnosis [ 10 , 11 , 17 ]. The aim of the present study was to evaluate the clinical presentation and long-term outcome of isotope-scan-confirmed SAT.…”

“…The current study included only patients who underwent a thyroid technetium scan, had results consistent with SAT, and lacked other conditions that can interfere with the scan results. We used isotope scanning with technetium, as it is an accurate non-invasive diagnostic tool for diagnosing SAT [ 10 , 11 , 17 ]. Our diagnostic approach differs from previous studies, in which diagnosis was based on a variety of inclusion criteria including clinical symptoms, laboratory findings, ultrasonography features, and biopsy findings, but neither a technetium scan nor iodine uptake findings were mandatory as diagnostic criteria of SAT [ 3 , 4 , 5 , 12 ].…”

“…Inclusion criteria were typical technetium scan findings consistent with thyroiditis, including low or absent tracer uptake in the thyroid gland in the thyrotoxicosis phase [ 10 , 11 , 17 ], and age above 18 years. Exclusion criteria included postpartum state (occurring within 12 months from the end of pregnancy), thyroid malignancy, and exposure to iodine by either iodine-containing contrast material or by medications (within 12 months prior to scan).…”

“…In most studies, radioiodine uptake or a thyroid isotope scan were not mandatory criteria for SAT diagnosis, despite the high yield in the differential diagnosis of thyrotoxicosis. A thyroid isotope scan, can for example, effectively differentiate between Graves’ disease and SAT [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. SAT is thought to have a viral origin and a genetic susceptibility [ 12 ].…”

The Old and the New in Subacute Thyroiditis: An Integrative Review

“…According to the stage of the disease, the tracer uptake loss can be seen in the whole or in part of the gland. It is also possible that even when SAT affects only a certain part of the gland, e.g., one lobe of the thyroid, the scan shows a complete lack of uptake in the whole gland due to the suppression of TSH levels and the consequent lack of stimulation of thyroid cells [86].…”