Primary Hyperparathyroidism: Does a Systematic Treatment Improve the Calcium and Bone Metabolism After Surgery?

Inclusion Criteria: * Postmenopausal women * Male patients * Biochemically proven PHPT, PTX planned * No evidence for osteoporosis Exclusion Criteria: * Postoperative hypocalcemia needing substitution with calcium and vitamin D/ 1-25-OH-Vitamin D * Cancer (lung, breast, prostatic, parathyroid cancer and thyroid carcinoma \>1cm) * Persisting or recurrent PHPT (postoperative hypercalcemia) * Four-gland hyperplasia * Multiple endocrine neoplasia (MEN) or hereditary PHPT * Familial hypercalciuric hypercalcaemia (Ca/creatinine ratio \< 0.01) * Phenylketonuria * Renal impairment (creatinine clearance \<30ml/h) * Severe hepatic disorder * Severe systemic disorder * Thyroid dysfunction * Immobilisation * Intake of drugs with potential effects on BMD like glucocorticoids, lithium, estrogen-replacement therapy, selective Estrogen-receptor modulators (sERMs), bisphosphonates in the last three months * Intake of drugs containing digoxin or digitoxin * Known allergy against any component of the study medication