Background. The practical interest in the mild form of primary hyperparathyroidism (PHPT) is attributable to the asymptomatic course of the disease and the difficulty of timely diagnosis due to the lack of a widespread study of the blood calcium level. In some cases, the detection of a normocalcemic variant of the mild form of PHPT can be considered as an early diagnosis of overt PHPT.
Description of the clinical case. The article considers a clinical case of diagnosis of normocalcemic variant of PHPT in a 42-year-old woman.
Conclusion. The initial stages of PHPT and mild forms are asymptomatic, patients rarely complain, which often leads to slowly progressive irreversible changes in a number of organs and systems: in the kidneys, causing the possible development of renal failure; in the gastrointestinal tract (GIT) with recurrent erosions and ulcers; in the bone skeleton with development of osteopenia and osteoporosis and, as a result, to a decrease in the quality of life and disability. The description of this clinical case demonstrates the importance of routine determination of calcium levels and vitamin D concentrations in the absence of complaints.

Keywords: normocalcemic variant, mild form, hypercalcemia, primary hyperparathyroidism, parathyroid hormone, calcium