Iodine Content and Distribution in Thyroid Specimens from Two Patients with Graves' Disease Pretreated with Either Propylthiouracil or Stable Iodine: Analysis Using X-Ray Fluorescence and Time-of-Flight Secondary Ion Mass Spectrometry

Abstract

Patients with Graves' disease can be medically prepared before surgery in different ways, which may have various effects on iodine stores. Thyroid specimens were collected at surgery from two patients pretreated with propylthiouracil (PTU) and stable iodine, respectively. A quantitative analysis of iodine content was performed using X-ray fluorescence (XRF) in frozen tissue and a qualitative analysis of aldehyde-fixed material with Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). Iodine concentrations were 0.9 mg/mL and 0.5 mg/mL in the thyroid tissue from the patients treated with PTU and stable iodine respectively. TOF-SIMS showed iodine in the follicle lumina in both. However, in the PTU case, iodine was also seen within the thyrocytes indicating accumulation of iodinated compounds from uninhibited hormone release. XRF and TOF-SIMS can be used to follow iodine distribution within the thyroid and the intricate processes following the different medical treatment alternatives in Graves' disease.

Figure 1

Light microscopy image (a) and TOF-SIMS image (b) of the tissue section from the PTU pretreated patient. The green in the TOF-SIMS image represents the signal from iodine and the red marks PO₃ ⁻ (signal from cell membranes). Iodine signals were mainly found within the follicle lumina but also in some areas outside the follicles, presumably in the thyrocytes. The iodine concentration was inhomogeneously distributed within some follicle lumina.

Figure 2

TOF-SIMS image of a second tissue section from the PTU pretreated patient. The green in the TOF-SIMS image represents the signal from iodine and the red marks PO₃ ⁻ (signal from cell membranes). Iodine signals were located within the follicle lumina, but also within thyrocytes.

Figure 3

Light microscopy image (a) and TOF-SIMS image (b) of the tissue section from the patient pretreated with stable iodine. The green in the TOF-SIMS image represents the signal from iodine and the red marks PO₃ ⁻ (signal from cell membranes). Iodine was located within the follicle lumina. The differences in iodine signal intensity indicate a difference in iodine concentration between the follicle lumina.