Normocalcemic Hyperparathyroidism and Treatment Resistant Depression

Abstract

In years past, primary hyperparathyroidism (pHPT) would often present itself as a problem related to bone disease or to kidney stones. Today, most patients with pHPT are so-called asymptomatic and discovered incidentally because of elevated levels of serum calcium and parathyroid hormone (PTH). Patients suffering from asymptomatic hyperparathyroidism may display a range of neuropsychiatric symptoms, including depression, anxiety, behavioral disturbances and psychosis, and reduced neurocognitive function. Table 1 shows typical signs and symptoms of pHPT, a condition that is more common in the elderly and in women. A prevalence of 21/ 1000 has been found in women aged 55-75 years (Table 1). The diagnosis of pHPT may easily be missed if not suspected by the clinician and if the appropriate biochemical tests are not performed. A high level of albumin-corrected calcium is often the sign that leads to further investigation. Other relevant biochemical tests are ionized calcium, urinary calcium excretion, phosphate, PTH, vitamin D, and creatinine. Patients with pHPT will usually, but not always, have an increased serum calcium level as well as an increased level of PTH. The level of vitamin D may be normal, but patients with pHPT more often have a vitamin D deficiency than matched controls. Figure 1 presents a flow chart that outlines a biochemical examination procedure for patients with treatment-resistant depression, in order to detect whether a patient suffers from HPT. We present a patient with pHPT and treatment-resistant depression, where the level of calcium was in the normal range. His symptoms disappeared after surgery. Our discussion of the case is placed in the context of recent literature on the topic of pHPT and neuropsychiatric symptoms.