Parathyroid Disorders: When the Calcium Balance Goes Wrong

Most people have four pea-sized parathyroid glands, on or near the thyroid gland in the neck. Despite the similar names, the parathyroid and thyroid glands are completely different and unrelated.

What the parathyroid glands do

The parathyroid glands' only job is to make parathyroid hormone (PTH), which keeps the body's balance of calcium and phosphorus right. When blood calcium falls too low, the glands release just enough PTH to bring it back to normal. PTH raises blood calcium by:

• making bone, where most of the body's calcium is stored, release calcium into the blood;
• helping the intestines absorb calcium from food;
• helping the kidneys hold on to calcium rather than flushing it out in urine.

Calcium builds and strengthens bones and teeth and helps the heart, muscles and nerves work normally. If the glands make too much or too little PTH, the balance is upset.

Too much: hyperparathyroidism

When the glands release extra PTH, the condition is hyperparathyroidism and blood calcium rises. Often a benign tumour makes one gland overactive; the extra hormone can also come from enlarged glands; very rarely the cause is cancer.

In the United States, about 100,000 people develop primary hyperparathyroidism — the form that begins in the glands themselves — each year, making it one of the most common hormonal disorders. It most often affects people aged 50 to 60, and women 3 to 4 times as often as men. It is usually caught early through routine blood tests.

It mainly affects bones, which can weaken as they release calcium, and kidneys, where excess calcium can form stones. Most people have no symptoms; when they appear they are often mild — muscle weakness, tiredness, depression, and aches in bones and joints. More severe disease can bring loss of appetite, nausea, vomiting, constipation, confusion, and increased thirst and urination.

Too little: hypoparathyroidism

When there is not enough PTH, the condition is hypoparathyroidism: the blood has too little calcium and too much phosphorus. Causes include injury to the glands, endocrine disorders and genetic conditions. Treatment aims to restore the balance of calcium and phosphorus.

Sources

• MedlinePlus, U.S. National Library of Medicine, "Parathyroid Disorders," drawing on the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). https://medlineplus.gov/parathyroiddisorders.html
• NIDDK, "Primary Hyperparathyroidism," used for how PTH raises calcium, how common the disorder is, who gets it, its effects and symptoms: https://www.niddk.nih.gov/health-information/endocrine-diseases/primary-hyperparathyroidism
• Rewritten in hubnx's own words.