Journal of Clinical and Scientific Research (Jan 2022)

Vitamin D status in primary hyperparathyroidism in 1990 and thence – Emergence of normocalcaemic presentation and diagnostic challenges – Utility of parathyroid function index

  • Chittari Venkata Harinarayan,
  • Honey Ashok,
  • Srinivasa Phanidhar Munigoti,
  • Shantanu Tandon,
  • Kadainti Venkata Subbaraya Sarma,
  • Anisha Sawkar Tandon,
  • Sherin Philip Chandy,
  • Dali Chandran

DOI
https://doi.org/10.4103/jcsr.jcsr_44_22
Journal volume & issue
Vol. 11, no. 3
pp. 167 – 174

Abstract

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Background: 25-hydroxyvitamin D (25OHD) levels much influence parathyroid hormone levels and bone disease in primary hyperparathyroidism (PHPT). With the emergence of the normocalcaemic PHPT (NCPHPT), repletion of the 25OHD level to rule out secondary hyperparathyroidism (SHPT) is essential. This may delay the diagnosis of PHPT, and a diagnostic tool like parathyroid function index (PF index) may help in the early diagnosis. Methods: The biochemical and hormonal profiles of 52 patients with PHPT were analysed and compared with first description in 1990. Patients were grouped based on symptoms and albumin-corrected serum calcium levels. Those with normocalcaemia were subgrouped into those with and without 25OHD deficiency. Data were extracted from the hospital's electronic medical records to find subjects with SHPT and normal controls and calcium-to-phosphate ratio (C/P ratio) and the PF index were calculated. Receiver operating characteristic curves to decide the cut-off values that help in identifying PF index and C/P ratio between various subgroups. Results: Sixty-two per cent (32/52) were asymptomatic, 40% (21/52) normocalcaemic, amongst which 48% (10/21) had normal 25OHD levels. Across all categories, the PF index was more sensitive, specific and superior compared to the C/P ratio in the diagnosis of PHPT (P = 0·02), NCPHPT (P = 0·03) or SHPT (P = 0·0001). PF index (>25·8) was more sensitive (90%), specific (96.51%), compared to C/P ratio (>0·211) (P = 0·04) in differentiating NCPHPT from SHPT. Conclusions: The prevalence of asymptomatic PHPT and NCPHPT is on the rise. PF index helps distinguish NCPHPT from SHPT minimising the time required for confirming the diagnosis post-25OHD repletion.

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