Endocrine Abstracts

Introduction: Vitamin D deficiency occurs more frequently in patients with primary hyperparathyroidism compared to general population, and is usually associated with an aggravated form of the disease. Current guidelines recommend measurement of vitamin D level in all patients with primary hyperparathyroidism, and their repletion if the levels are <50 nmol/l.

Case report: We present a 56 years old Caucasian lady who underwent right parathyroidectomy & thyroid lobectomy for right parathyroid carcinoma in 1998. Her initial serum parathyroid level was 48.2 pmol/l (1.1–6.4). Postoperatively, her parathyroid level improved to 7.5 pmol/l but never came back to normal. She was followed up in endocrine clinic for persistent normocalcaemic hyperparathyroidism with no evidence of recurrent parathyroid cancer. In January 2010 her parathyroid level was 7.8 pmol/l with concomitant vitamin D level being 80 nmol/l (>50 nmol/l). She was started on ergocalciferol 400 IU twice daily. After 6 months, her parathyroid levels were 4.3 pmol/l which suggested secondary hyperparathyroidism due to relative vitamin D deficiency. In March 2012, despite being on vitamin D supplementation, her parathyroid levels were elevated at 6.6 pmol/l with vitamin D level being 86 nmol/l. She was advised to continue with same dose of vitamin D supplement. In March 2014, her parathyroid level increased further to 8.6 nmol/l with her being vitamin D replete at 107 nmol/l. This time it was decided to increase the dose of vitamin D to 2000 IU/day. After 6 months of treatment with increased dose of vitamin D, her parathyroid level normalized to 4.6 pmol/l with vitamin D levels of 152 nmol/l. She was normocalcaemic during all this time.

Discussion: In this patient, her parathyroid levels normalised after achieving a vitamin D level, which was higher then usually recommended level. In selected patients, we may need to aim for a higher vitamin D level before seeing an improvement in parathyroid levels.