Endocrine Abstracts

JOINT854

Introduction: The 99mTc-sestamibi scintigraphy is commonly used for preoperative localization of the affected gland in primary hyperparathyroidism (PHPT) due to its affinity for well-perfused, mitochondria-rich tissues. However, false-negative results occur in 12-25% of cases. Several factors can affect the sensitivity of 99mTc-Sestamibi scintigraphy, including the size and location of the affected gland, the lesion’s mitochondrial and fat composition, P-glycoprotein expression, the presence of multiglandular disease, and coexisting thyroid pathology.

Aim: To analyse the association between the histopathological and laboratory findings of patients who underwent parathyroidectomy and had false-negative results in 99mTc-Sestamibi scintigraphy.

Methods: A retrospective study was conducted on patients diagnosed with PHPT who underwent parathyroidectomy and had a 99mTc-Sestamibi scintigraphy performed.

Results: A total of 143 patients were identified and included in the study. The sample was predominantly composed of women (84. 6%) with a mean age of 58. 4±13. 7 years. The preoperative laboratory study revealed median values of ionized calcium of 1. 41 mmol/l (IQR:1. 37–1. 50), phosphate of 2. 6 mg/dL (IQR:2. 2–3. 0), PTH of 178. 1pg/mL (IQR:138–291. 2), and 25-OH vitamin D of 19. 4 IU (IQR:14. 0–27. 4). The histopathological study revealed 104 (72. 7%) typical adenomas, 5 (3. 5%) atypical adenomas, 6 (4. 2%) carcinomas, 20 (14. 0%) hyperplasia, and 8 (5, 6%) other histology. The 99mTc-Sestamibi scintigraphy allowed the localization of the affected glands in 123 (86. 0%) cases. Comparatively, in the remaining 20 (14. 0%) cases where the scintigraphy was negative, the frequency of typical adenoma was significantly lower (50. 0% vs. 76. 4%; P=0. 014). However, no significant differences were found regarding hyperplasia (20. 0% vs. 13. 0%), atypical adenoma (0. 8% vs. 3. 3%), and parathyroid carcinoma (0% vs. 4. 9%). In the scintigraphy-negative group, the lesions tend to be smaller (median weight 0. 46g [AIQ: 0. 61] vs. 0. 74g [AIQ: 1. 02]; P=0. 035). The analysis of laboratory parameters related to phosphocalcic metabolism revealed that vitamin D levels were significantly higher in patients with a negative scintigraphy result (23. 6 UI [AIQ: 19. 3-23. 6] vs. 17. 6 [AIQ:13. 9-25. 7]]; P=0. 033).

Discussion: PHPT is caused by benign single-gland adenoma in 85% of cases, and precise identification of the affected gland can be challenging. The lesions in the negative scintigraphy group were generally smaller. Both groups present a high prevalence of Vitamin D deficiency, which is linked to a higher volume of parathyroid adenoma. The group with negative scintigraphy showed a higher vitamin D level, which is consistent with the literature.