"I've got what?" exclaimed the incredulous 48-year-old post- office worker upon learning the cause of his recent kidney-stone attack. "You have primary hyperparathyroidism," I repeated and proceeded to explain how a malfunctioning pea-sized gland in his neck could cause that painful kidney stone to form. Like this man, surprisingly few patients are even aware that parathyroid glands exist, let alone how they work and all the problems they can cause. In fact, one of my medical school professors referred to hyperparathyroidism as a disease of "stones, bones, and abdominal groans," based on the body parts most commonly affected in advanced stages of the disease.


There are four tiny parathyroid glands, each nestled into the back of one of the "wings" of the butterfly-shaped and much larger thyroid gland that straddles the windpipe just below the Adam's apple. Their job is to make and secrete parathyroid hormone (PTH)—a protein that keeps the blood calcium level within a narrow normal range. Too much calcium causes kidney stones, dehydration, constipation, nausea, and vomiting. Too little calcium can cause muscle cramps, spasms, and convulsions.

PTH exerts its regulatory command by its effects on three areas of the body—kidneys, bones, and intestines. Once in a while, possibly because of a genetic deficiency, one of the four parathyroids (occasionally two, but rarely all four) begins to produce too much PTH. As a result, calcium is leached from the outer, or cortical, layer of bone. This can lead to osteoporosis of the wrist and hip (the spine is not affected as much because it has less cortical-bone content). The resorbed bone calcium causes the blood level to rise, flooding the kidneys with calcium and increasing the risk of kidney stones and eventual irreversible kidney damage. Other problems linked to the high blood calcium and PTH levels are recurrent stomach ulcers, inflammation of the pancreas, muscle weakness, and sundry cardiovascular disorders.

Before 1971, when the automated blood chemistry analyzer became a routine fixture in hospitals and doctors' offices, physicians had to actually think of the diagnosis and then order the appropriate specialized blood test to prove it. Consequently, by the time a hyperparathyroidism diagnosis was made, the kidneys were beyond repair, the bones were collapsing and fracturing, and the patient was in pain from stomach ulcers, pancreatic inflammation, or severe constipation.

Nowadays, those automated blood tests pick up most cases of hyperparathyroidism in people without symptoms because they measure, among many other things, the high serum calcium level that is the earliest tip-off to the condition. The diagnosis is then cinched by ordering a blood parathyroid hormone level test and finding it elevated. This ease of diagnosis has revealed that parathyroid disease, formerly thought to be rare, actually occurs in more than 2 percent of people over age 50 and is three times more common in women than in men.

The treatment is surgical removal of the guilty parathyroid gland through a small incision in the lower neck, under regional anesthesia. Patients typically go home the same day. Sound easy? Anything but! It takes a skilled and experienced surgeon to identify the overactive gland and remove it without damaging surrounding tissues, muscles, and nerves.

The internist's or endocrinologist's job is to select surgical candidates from the myriad people with the disease. The need for surgery is clear for patients who already have complications or are at increased risk for them (because of very high blood or urine calcium levels or evidence of beginning bone loss). The dilemma concerns those who have no complications and whose risk factors are minimal; a significant minority may never develop problems. The age of 50 seems to be the consensus dividing line since increasing age brings with it other confounding illnesses, some of which might make surgery hazardous.

A medical treatment using a new class of drugs called calcimimetics, such as cinacalcet (Sensipar), is being studied and might prove beneficial. One limited trial has shown promising results, but long-term follow-up studies are needed.

There was not much doubt about what to do with the postal worker; he already had a complication—a painful bout with a kidney stone. He underwent an uneventful operation at the hands of an experienced parathyroid surgeon and likely will have a stone-free future.