Advances in Functional Imaging of Differentiated Thyroid Cancer

The present review provides a description of recent advances in the field of functional imaging that takes advantage of the functional characteristics of thyroid neoplastic cells (such as radioiodine uptake and FDG uptake) and theragnostic approach of differentiated thyroid cancer (DTC). Physical and biological characteristics of available radiopharmaceuticals and their use with state-of-the-art technologies for diagnosis, treatment, and follow-up of DTC patients are depicted. Radioactive iodine is used mostly with a therapeutic intent, while PET/CT with 18F-FDG emerges as a useful tool in the diagnostic management and complements the use of radioactive iodine. Beyond 18F-FDG PET/CT, other tracers including 124I, 18F-TFB and 68Ga-PSMA, and new methods such as PET/MR, might offer new opportunities in selecting patients with DTC for specific imaging modalities or treatments.

Thyroid pathologies in nuclear medicine

The presented work describes the thyroid pathologies and the nuclear-medical diagnostic approach, in order to obtain a differential diagnosis and the monitoring of various neoplasms; specifically, it describes the importance of radiometabolic treatment with iodine 131, after thyroidectomy surgery. Through a study conducted in patients suffering from thyroid disease, undergoing metabolic radiotherapy, it is shown that, with equal distribution of radioiodine, uptake with at least 3700 MBq of therapeutic dose is obtained. All this can be seen through the whole body scintigraphic framework, obtained through the use of the double-headed gamma camera with collimators for high emission energies. Radiometabolic treatment is effective in patients with a high risk of relapse, while radioiodine treatment is not recommended in low-risk patients.

False-Positive Radioiodine Uptake in Simple Ovarian Cyst in a DTC Patient: A Case Report

Abnormal radioildine uptake can be caused by various pelvic lesions in differentiated thyroid cancer patient. Here we presented an abnormal uptake in the left side of the pelvic cavity on postablative I-131 scintigraphy in a 51-year-old woman with history of stage T1aN1M0 papillary thyroid cancer. The SPECT/CT fused imaging revealed the lesion in the left ovary. Laparoscopic bilateral adnexectomy showed a left ovarian mass (5 cm) and pathologic finding showed a simple ovarian cyst. The nonstimulated Tg immediately decreased to 143 ng/ml after bilateral adnexectomy 3 days later and to 0.109 ng/ml after 4-month follow-up. Timely intervention measures are very necessary for patients with ovarian cyst with abnormally elevated Tg level.

A comparison of thyroidal protection by iodine and perchlorate against radioiodine exposure in Caucasians and Japanese

Radioactive iodine released in nuclear accidents may accumulate in the thyroid and by irradiation enhances the risk of cancer. Radioiodine uptake into the gland can be inhibited by large doses of stable iodine or perchlorate. Nutritional iodine daily intake may impact thyroid physiology, so that radiological doses absorbed by the thyroid as well as thyroid blocking efficacy may differ in Japanese with a very rich iodine diet compared to Caucasians. Based on established biokinetic–dosimetric models for the thyroid, we derived the parameters for Caucasians and Japanese to quantitatively compare the effects of radioiodine exposure and the protective efficacy of thyroid blocking by stable iodine at the officially recommended dosages (100 mg in Germany, 76 mg in Japan) or perchlorate. The maximum transport capacity for iodine uptake into the thyroid is lower in Japanese compared to Caucasians. For the same radioiodine exposure pattern, the radiological equivalent thyroid dose is substantially lower in Japanese in the absence of thyroid blocking treatments. In the case of acute radioiodine exposure, stable iodine is less potent in Japanese (ED50 = 41.6 mg) than in Caucasians (ED50 = 2.7 mg) and confers less thyroid protection at the recommended dosages because of a delayed responsiveness to iodine saturation of the gland (Wolff–Chaikoff effect). Perchlorate (ED50 = 10 mg in Caucasians) at a dose of 1000 mg has roughly the same thyroid blocking effect as 100 mg iodine in Caucasians, whereas it confers a much better protection than 76 mg iodine in Japanese. For prolonged exposures, a single dose of iodine offer substantially lower protection than after acute radioiodine exposure in both groups. Repetitive daily iodine administrations improve efficacy without reaching levels after acute radioiodine exposure and achieve only slightly better protection in Japanese than in Caucasians. However, in the case of continuous radioiodine exposure, daily doses of 1000 mg perchlorate achieve a high protective efficacy in Caucasians as well as Japanese (> 0.98). In Caucasians, iodine (100 mg) and perchlorate (1000 mg) at the recommended dosages seem alternatives in case of acute radioiodine exposure, whereas perchlorate has a higher protective efficacy in the case of longer lasting radioiodine exposures. In Japanese, considering protective efficacy, preference should be given to perchlorate in acute as well as prolonged radioiodine exposure scenarios.

Lyme Disease: An Autoimmunity-Based “Destructive Thyroiditis” or Just Another “Non-Thyroidal Illness”?

There is considerable evidence that some Borrelial (Lyme spirochetal) proteins share significant antigenic properties with several thyroid-related proteins (e.g. TSH receptor, thyroglobulin, thyroid peroxidase) and can induce thyroid autoimmunity, sometimes associated with Hashimoto’s thyroiditis and perhaps also a “destructive thyroiditis” such as “silent” thyroiditis or “Hashitoxicosis.” As an acute illness, Lyme disease may also constitute a “non-thyroidal illness” capable of perturbing thyroid function tests without causing thyroid dysfunction. We report a 22-year old woman admitted with an acute paranoid schizophrenia, thyroid function tests consistent with autoimmunity, transient thyrotoxicosis (tachycardia, lid-lag, brisk DTR’s) and a greatly reduced radioiodine uptake. The thyroid was not palpably enlarged, nodular or tender. On screening assay, reactivity was demonstrated to 4 of 13 Borrelial proteins. Anti-Lyme IgM but not IgG, antibodies, were positive. This was consistent with recent Lyme disease infection. Serum TSH (NL: 0.358-3.74 mcU/ml), Free T4 (NL: 0.76-1.46 ng/dl), and Free T3 (NL: 2.18-3.98 pg/ml) were, respectively: Day1: 0.087 mcU/ml (suppressed), 1.52 ng/dl (slightly elevated), 2.07 pg/ml (slightly reduced); Day2: 0.148 (suppressed), 1.18 (normal), no FT3; Day4: 0.827 (normal), no FT4 or FT3; Day5: 1.66 (normal), 0.89 (normal), 1.77 (low). Anti-Tg and Anti-Peroxidase antibodies were both moderately elevated. Thyroid Stimulating Immunoglobulins were not elevated. The radioactive iodine uptake on Day4 was 2.8% (NL: 15-30% at 24 hr). Thyroid ultrasonogram was normal. An attractive explanation is that Lyme disease triggered a “destructive thyroiditis,” perhaps but not necessarily mediated by thyroid autoimmunity. This would account for the brief interval of thyrotoxicosis accompanied by a very low radioiodine uptake. Alternatively, Lyme disease, as an acute process, would expectedly be capable of eliciting the thyroid function abnormalities of “non-thyroidal illnesses” in general, as would acute psychosis, well-known to often resemble Graves’ disease at admission.