The importance of laboratory analyses in unmasking parathyroid adenoma in a patient with breast cancer: a case report of persistent hypercalcaemia with low vitamin D status

<p><strong>Background:</strong> Parathyroid adenoma is a frequent cause of hyperparathyroidism. Its association with D hypovitaminosis can complicate this pathological state, especially in case of delayed surgical intervention. </p> <p><br /><strong>Case presentation:</strong> This case report presents a 77-year-old female patient with a complex medical history including dyslipidemia, hypertension, who developed primary hyperparathyroidism due to a parathyroid adenoma. The persistent hypercalcemia, elevated parathyroid hormone (PTH), and parathyroid scintigraphy led to the diagnosis, but the low 25-hydroxyvitamin D level complicated the picture. Due to personal decisions and the COVID-19 pandemic, surgery was delayed for six years, resulting in complications such as vitamin D deficiency-induced immunosuppression and osteoporosis. Post-surgical outcomes were favorable, with normalization of biochemical markers and stabilization of comorbid conditions. </p> <p><br /><strong>Conclusion:</strong> This case highlights that timely multidisciplinary management is essential in primary hyperthyroidism, as surgical delay worsens complications, yet parathyroidectomy can still reverse outcomes even after years of progression. </p>