Effects of Hyperparathyroidism
When a parathyroid gland enlarges and produces too much PTH, the blood calcium level becomes high, bones may lose calcium, and kidneys may excrete too much calcium. These changes may give rise to symptoms and signs such as polyuria, thirst, fractures, and kidney stones.

Neuropsychiatric symptoms associated with primary hyperparathyroidism include anxiety as well as cognitive and psychotic presentations. However, the most common presentation is depression with associated apathy.⁵ In a prospective study of 34 patients with hyperparathyroidism, Velasco and colleagues⁶ found that approximately one-third of participants had no psychiatric symptoms, one-third had affective symptoms (with or without paranoia), and one-third had cognitive impairment. Affective symptoms were most common in patients with modest elevations in electrolyte levels, while cognitive deficits were more often related to higher calcium concentrations.

Hypercalcemia. The severity of psychiatric symptoms in patients with hyperparathyroidism often correlates with the increase in serum calcium levels. Calcium performs a crucial role in nerve conduction. Consequently, it is no surprise to find out that some common symptoms of parathyroid hyperactivity and high calcium levels are related to the nervous system.

Other symptoms have to do with the muscular system, which uses changes in intracellular calcium concentration to initiate and transmit the command to contract muscle fibers. Improper regulation of calcium levels may result in muscle cramps and weakness. The heart is a muscle, and therefore its conduction system is also vulnerable, with possible shortening of the QT interval, rhythm disturbances, and even cardiac death.

The skeletal system not only functions as the reservoir of calcium for the body, but calcium phosphate(Drug information on calcium phosphate) is an essential ingredient of bone tissue. Consequently, a hyperactive parathyroid system contributes to osteoporosis and vulnerability to bone fractures.

When hypercalcemia is present, it is important not only to screen for hyperparathyroidism but also to rule out other possible underlying conditions, such as malignancy and drug-induced elevations in calcium levels.

Case Note
Already, early in the process of screening for elevated calcium levels in my many patients who are receiving lithium(Drug information on lithium), I have identified a patient with hypercalcemia and a markedly elevated PTH level, which may indicate hyperparathyroidism. She is a 50-year-old woman with schizoaffective disorder who has been receiving long-standing lithium therapy and is undergoing further evaluation by an endocrinologist. All of us are hopeful that her recent cognitive decline and mental apathy will prove to be reversible.