Introduction: Surgery for primary hyperparathyroidism (PHPT) is traditionally deemed to be successful if serum calcium levels return to normal 6 months after parathyroidectomy. Regular monitoring of serum calcium and parathyroid hormone (PTH) in the follow-up of patients after parathyroidectomy for PHPT has drawn attention to the presence of a normocalcemic group of patients with elevated PTH (NCePTH) during the post-operative period. The etiological factors and mechanisms underlying this condition, its consequences, and the possibility of treatment are the object of this study.
Materials and methods: We conducted an unlimited PubMed search updated on March 31, 2017, which yielded 1628 results. We selected 37 articles, 33 of which included cases of NCePTH in their series and 23 performed statistical studies to assess factors associated with NCePTH.
Results: The maximum mean prevalence of NCePTH in the various series was 23.5%, ranging from 3 to 46%. Many factors were associated with NCePTH. The most important were higher pre-operative PTH, low pre-operative 25 (OH) D3, lower pre-operative creatinine clearance and greater adenoma weight. The origin of NCePTH may be multifactorial, since several factors were implicated in the etiology. NCePTH does not seem to be related to an increase in PHPT recurrence, although this possibility should not be dismissed. Vitamin D deficiency should be corrected. Treatment with calcium supplements seems to be clearly beneficial.
Conclusion: The prevalence of NCePTH is high. The causes of secondary hyperparathyroidism should be investigated carefully. Patients require treatment and long-term follow-up.
Keywords: Hyperparathyroidism, Primary; Parathyroid hormone; Parathyroidectomy; Post-operative hyperparathyroidism; Post-operative period; Review.