Endocrine Abstracts

Objective: Primary hyperparathyroidism (PHP) is a common endocrine disorder diagnosed biochemically, common use of autoanalyzers increased the incidence of PHP throughout last decades. Minimally invasive parathyroidectomy has been preferred to the explorative surgical approach due to shorter operating time, lower complication rate, and smaller incision size. Thus localization studies have become very important. We aimed to investigate clinical and laboratory characteristics of patients, causes and success of localization studies in a large cohort of PHP in a retrospective manner.

Methods: Study included 443 patients with PHP diagnosed between January 2010 and January 2021. Clinic characterisrics, biochemical parameters, findings of imaging studies for localization and postoperative histopathological results were examined. Ultrasonography (US), US-guided PTH-washout analysis; ^99mTechnetium -Sestamibi/¹²³Iodine Scintigraphy(MIBI -SPECT/CT) were used as initial localization techniques. Four Dimensional Computed Tomography(4D-CT), 18F-Fluorocholine Positron Emision Tomography (18F-FCH PET/CT) were used as advanced imaging methods for patients whose parathyroid lesions could not be localized with initial methods.

Results: 79%(n=350) of patients were female, the mean age was 59.9±13. Mean±SD serum Calcium(Ca), Phosphate(PO₄) and Parathormone(PTH) levels were 10.9± 0.8 mg/dl, 2.7 ± 0.5 mg/dl and 192.7 ± 82.3 pg/ml, respectively. 12.9% of the patients had normocalcemic hyperparathyroidism. The incidence of osteoporosis was 42.6%(n=150). PTH levels were significantly higher in the patient group with osteoporosis(P=0.017). The most common surgical method was minimally invasive surgery at 81.2%. Histopathological evaluation resulted in single adenoma in 98.1% of patients and hyperplasia in 1.5%, cancer in %0.4. A significant positive correlation was found between adenoma volume with serum Ca and PTH levels (P<0.001). The most common location of parathyroid lesions was right lower pole of thyroid gland with 49.6%. 4D-CT and 18F-FCH PET/CT were used in 60 and 43 patients, respectively. Positive predictive values(PPV) of imaging modalities: US, US-guided PTH-washout analysis, MIBI-SPECT/CT, 4D-CT and 18F-FCH PET/CT were 83.6%, 91.8%, 81.2%, 88.9% and 97.7%, respectively.

Conclusion: Calcium and PTH levels could give an idea for the size of the adenoma. Using initial localization studies (i.e US combined with PTH washout, MIBI-SPECT/CT) most of the adenomas could be localized. For those patients who required advanced imaging modalities, 4D-CT is highly effective, but 18-FCH PET/CT has the highest PPV for parathyroid adenoma localization.