Endocrine Abstracts

Background: Hypercalcaemia in endocrine patients often poses diagnostic challenge, with hyperparathyroidism and familial hypocalciuric-hypercalcaemia(FHH) being common differentials. This case-report presents unique and complex aetiology, underscoring need for comprehensive evaluation.

Case-Description: We present case of 57-year-old Caucasian-woman referred to our clinic with persistently elevated calcium and parathyroid hormone(PTH) levels over several months. Her medical history included bipolar disorder treated with Lithium (800mg) for 17 years. Family history was unremarkable, and patient was asymptomatic upon presentation. Laboratory evaluation revealed elevated PTH(79ng/l; reference-range:11-64ng/l), corrected-serum-calcium levels of 2.72 & 2.92mmol/l (ReferenceRange: 2.20-2.60mmol/l),24-h urinary calcium excretion of 5.1mmol/24hr (reference range: 2.5-7.5mmol/l), VitaminD deficiency (4.2ug/l;ReferenceRange:>20ug/l), normal electrolytes and renal functions, and subclinical hypothyroidism. Vitamin D was replenished, but persistent hyperparathyroidism with hypercalcaemia was observed during follow-up. Imaging studies, including Sestamibi-scan, DEXA-scan, and ultrasound of kidneys, thyroid, and parathyroid, failed to identify any abnormality. Considering possibility of Lithium-induced-hyperparathyroidism, consultation with psychiatrist was recommended to discuss discontinuing Lithium but declined by patient. Regular follow-ups and adequate hydration were advised. Serial calcium measurements demonstrated fluctuations between peak of 3.09 and nadir of 2.45mmol/l, associated with intermittent nocturia and increased thirst. Four years after initial presentation, patient became grandmother, and her granddaughter was found to have mild hypercalcaemia. Further investigations confirmed mild hypercalcaemia in patient’s daughter as well. Familial cause of hypercalcaemia was suspected, leading to genetic testing of three generations. Results revealed Familial Hypocalciuric Hypercalcaemia. This diagnosis, coupled with persistent nocturia and thirst, prompted initiation of Cinacalcet 30mg twice daily. Gradual but sustained response was observed, culminating in normalization of hypercalcaemia, with last corrected calcium level measuring 2.61mmol/l.

Discussion: This case report highlights intricate aetiological complexity underlying what initially appeared to be straightforward case of primary hyperparathyroidism-induced hypercalcaemia. It underscores significance of considering detailed family history and need for persistent follow-up to unravel complex diagnostic scenarios.