Low blood calcium is a rare problem and one that we had never even considered when we saw him in the clinic. The emergency room doctors hadn’t thought of it either. But because calcium is part of a routine blood test, the abnormal value was right there for us to see.
In seconds, what had been a disjointed clinical story clicked into focus. His heart failure, which we had diagnosed in the clinic? Probably due to a lack of calcium, which helps sustain cardiac muscle contraction. All muscles require calcium to work. When nerve impulses reach muscles, calcium ions flowing into or out of the muscle cells are the key signal allowing that muscle to contract and relax. If calcium levels are low, the signals do not get transmitted correctly.
Low calcium also explained his twitching hands, the symptom that had brought him to clinic in the first place. Without enough calcium around, skeletal muscles can unpredictably go into spasm. Andrew just didn’t happen to have a spasm when we examined him. If we had suspected he had low blood calcium, we could have elicited a spasm by temporarily cutting circulation to his arm with a tourniquet, which would have further decreased the amount of calcium available to his muscles and produced the telltale twitching. But since we assumed he was imagining the spasms, this hadn’t occurred to us.
The diagnosis might even explain Andrew’s feeling of being possessed. It turns out that low calcium levels can make people anxious or even psychotic, probably by changing the way nerve signals are transmitted in the brain.
Before I could help Andrew, though, I still needed to fill in a crucial missing part of the picture. How in the world had he become so severely depleted of calcium?
Calcium is one of the most carefully regulated elements in the body, taken in through food and then sustained, in a steady state, in the bloodstream and bones through a network of hormones. Vitamin D also plays an important role by helping regulate the amount of calcium in the kidneys, bones, and blood. The system is so effective that it will leach calcium from bone, retrieve it from the urine, or absorb it from the intestinal tract rather than allow the blood calcium level to fluctuate. People usually exhibit low calcium levels only if they have suffered a serious breakdown of one or more of these regulatory factors that normally provide checks and balances to keep calcium in the appropriate range.
The normal system that regulates calcium can go wrong in a number of places. Neck surgery can disrupt the production of calcium-regulating hormones made there. Lack of exposure to sun or an extreme lack of vitamin D in a person’s diet can lead to severe calcium deficiency. Kidney problems can also disrupt the action of the calcium-regulating network.
It turned out that Andrew had at least three of these factors at play. Once he was hospitalized, he told us that he rarely if ever went outside, except in emergencies. He therefore had no exposure to sunlight and no skin synthesis of vitamin D. And his diet was extremely limited and bizarre: For years, he had subsisted mainly on white bread and a few other items, none of which had much calcium or vitamin D. To make matters even worse, he was taking furosemide, a medicine for high blood pressure that has the side effect of preventing calcium from being retained by the kidneys.
The result: severe calcium and vitamin D deficiencies, then osteoporosis as his body drained his bones of calcium, and finally, when his reserves were exhausted, the low blood calcium levels, the lack of normal levels of calcium in his nerves and muscles, and the resultant twitching of his hands.
We took him off furosemide and gave him high-dose vitamin D and intravenous calcium, correcting his calcium levels. The treatment worked for his physical symptoms. Within a week his heart function improved, and the telltale hand twitching that had bothered him so much was finally gone. We waited for his anxiety to diminish as well, but he remained agitated.
Andrew left the hospital a few days earlier than we would have liked, and only reluctantly came back to follow up with us and with his psychiatrist. I don’t know if he eventually expanded his diet or started to venture outside. Unfortunately, his psychiatric disease didn’t improve with treatment of his low calcium and was probably the cause, rather than the consequence, of the calcium problem. But at least—if he took the vitamins and calcium supplements we prescribed—his hands would never be possessed again.
Dena Rifkin is a physician at the University of California, San Diego. The cases described in
Vital Signs are real, but names and certain