100 Hyperthyroidism

Clinical Presentation

A 26-year-old woman presents with clinical and biochemical evidence of hyperthyroidism.

Fig. 100.1

Technique

• ^99mTc-pertechnetate, 10 mCi (370 MBq) intravenously.

• Planar imaging of the neck with a pinhole collimator 20 minutes later (Figs. 100.1 and 100.2).

Image Interpretation

Anterior view from the ^99mTc-pertechnetate scan, with pinhole collimator 4 cm from the neck (Fig. 100.1), demonstrates intense, increased uptake throughout the substantially enlarged thyroid. The intense uptake in the thyroid results in little visualization of the background tissues. A pyramidal lobe is appreciated extending superiorly from the upper aspect of the left lobe. A 6-hour radioiodine uptake assessment earlier the same day revealed a markedly elevated uptake of 80% (normal, 5–20%). The up-take and scan findings are consistent with Graves disease.

Therapy

An oral dose of 13 mCi of ¹³¹I was administered. The patient was still hyperthyroid 10 months later and was referred back to nuclear medicine. The repeated scan (Fig. 100.2) again demonstrated intense up-take throughout an enlarged thyroid, although it was smaller than on the initial study. There was again visualization of a pyramidal lobe and little visualization of the background tissues. Repeated 6-hour radioiodine uptake was 47%, significantly less than on the original study, but still elevated. She was retreated with 9 mCi of ¹³¹I, and her hyperthyroidism has not recurred.