- Primary hyperparathyroidism (PHPT) is characterised by elevated serum calcium levels due to elevated levels, or insufficient suppression, of parathyroid hormone (PTH).- The incidence of PHPT has increased in recent years. This is mainly the result of more frequently performed routine measurements of serum calcium, e.g. as part of postmenopausal screening.- The classically described features of PHPT - bones and stones - are not always observed and most patients are asymptomatic.- Diagnosis of PHPT is only established by biochemical testing, not by imaging.- Ultrasound and technetium-99m sestamibi SPECT-CT are the first-choice imaging modalities. These investigations are necessary to localize the parathyroid adenomas and thereby facilitate minimal invasive parathyroidectomy (MIP).