Endocrine Abstracts

Introduction: Serum parathormone (PTH) levels may remain elevated in some patients after surgery despite achievement of normal serum Ca levels. The factors contributing to this phenomenon have not been fully elucidated yet. In this study, we retrospectively analysed the data of patients whose serum Ca levels returned to normal after parathyroid surgery in our center.

Patients and methods: Computer records of 35 patients who had undergone parathyroid surgery and achieved normal serum Ca levels were retrospectively analysed. Despite serum Ca values within the normal ranges, patients were divided into two groups according to their PTH values 6 months after surgey (elevated PTH (ePTH) group (PTH ≥65 pg/ml) and low PTH (lPTH) group (PTH <65 pg/ml)). Fifteen patients were classified as having ePTH and 20 as IPTH. The frequency of ePTH was determined as 42%. The mean pre and postoperative PTH levels in ePTH and IPTH groups were 265±119, 94±32 and 206±136, 39±17 pg/ml, respectively. The mean pre and postoperative 25(OH) vitamin D3 levels in ePTH and IPTH groups were 12±7, 22±11 and 22±14, 32±12 ng/ml, respectively.

Results: Although ePTH group had higher preoperative PTH values as well as lower pre and postoperative 25 (OH) vitamin D3 levels, there was no statistically significant difference between the groups. For the remaining parameters, two groups had similar results.

Discussion: Several hypotheses have been proposed to explain the etiopathogenesis of persistently elevated PTH values despite normal Ca levels following parathyroid surgery. Suggested causes of this phenomenon include 25 (OH) vitamin D3 deficiency, secondary hyperparathyroidism resulting from insufficient renal function, stimulation of PTH secretion induced by relative hypocalcemia postoperatively, and increased bone turnover. However, this condition may also indicate possible recurrence due to multiglandular hyperplasia rather than a single parathyroid adenoma.