Hypercalcaemia can lead to many neuropsychiatric symptoms from fatigue, lethargy, anxiety, irritability, and insomnia to impaired concentration and memory, depression, delirium, and psychosis. Primary hyperparathyroidism (PHPT), which is the most common cause of hypercalcaemia, is a relatively common disorder affecting 1 in 500 women and 1 in 2000 men aged over 40 years. A patient, with a diagnosis of Alzheimer's disease, subtype mixed, had hypercalcaemia on admission which wasn't corrected until 4 months of the admission had passed. Calcium correction precipitated a marked improvement in the patient's mental state. In order to learn from this incident, an audit was carried out to look at possible gaps in performing blood tests, and how abnormal calcium levels can affect patients’ mental states.

Retrospective data collection was performed to obtain blood results for all patients -aged 40 years or above- admitted to inpatient wards in South Essex within a six month period (from April 2022 to September 2022). A total number of 333 patients (173 males and 160 females) were identified.

Bone Profile was checked in 248 patients (127 males and 121 females). Twelve patients were found to have hypercalcaemia on admission - mean age 65.7 years, female: male ratio of 3:1. No patients were found to have hypocalcaemia.

Hypercalcaemia was addressed in only 2 of 12 patients. Parathyroid hormone (PTH) was tested either before or during admission to mental health services in 6 patients, PTH was found to be elevated (greater than 9.3 pmol/L) in 4 patients (2 males and 2 females), below the midpoint of the reference range in one patient, and below the lower limit of the reference range in one patient.

Patients with hypercalcemia had different diagnoses - anxiety, depression, adjustment disorder, mania, psychosis, and dementia. It was the first admission for three patients with a mean age of 76 years. Six patients were known to services but it appeared that the recent admissions were associated with hypercalcaemia. Active management of hypercalcaemia in 2 patients resulted in improvement in their mental state.

We found that risk of PHPT in mental health inpatients aged over 40 years old was increased by 1.45% (95% CI: -0.0620% to 5.6256%, P = 0.0390) in females, and was increased by 1.52% (95% CI: 0.3573% to 5.5031%, P < 0.0001) in males. Hereby, testing for bone profile should be routinely recommended for mental health patients.