In recent years, the understanding of the epidemiology, symptoms and strategies for managing patients with hyperparathyroidism has changed significantly. The most common cases in clinical practice are of sporadic primary hyperparathyroidism, which today ranks third in prevalence among endocrine diseases (the frequency of occurrence in the adult population is, on average, 1–2%). In primary hyperparathyroidism, solitary parathyroid adenoma is detected in up to 85% of all cases. The only treatment is radical surgical removal of pathologically altered parathyroid tissue. Early diagnosis and treatment of hyperparathyroidism makes it possible to avoid severe lesions of the skeletal bones and visceral organs. A diagnostically challenging clinical case of a combined onco-endocrine pathology in a 70-year-old patient is presented. The main difficulties in the initial diagnosis were associated with the absence of pathognomonic symptoms of the disease, which was often completely asymptomatic. The most urgent problem appears to be the topical diagnosis of pathologically altered parathyroid glands. Therefore, there is a need to develop an algorithm for the combining and sequential use of existing medical imaging methods.