Primary hyperparathyroidism is systemic, polymorphic disease. Authors present a case of woman suffered from primary hyperparathyroidism misdiagnosed as disseminated neoplastic disease. There was shown a clinical picture complex, difficulties in diagnostic process, treatment and factors provided mistakes in therapy. The work lays stress on importance of routine testing of calcium in serum. It makes a contribution in diagnosis of hyperparathyroidism in symptomless or preclinical phase - before appearance metabolic and organ complications.