Hypoparathyroidism

What parathyroid hormone does

Most people have four small parathyroid glands, each about the size of a grain of rice, behind the thyroid gland. They release PTH when blood calcium drops. PTH raises calcium by releasing it from bone, reducing calcium loss in the urine, and activating vitamin D in the kidneys so the gut absorbs more calcium. It also helps the kidneys get rid of phosphate.

Without enough PTH, blood calcium falls, phosphate rises, and the kidneys lose calcium in the urine.

Causes

• Neck surgery: the most common cause. Thyroidectomy, parathyroid surgery and surgery for head and neck cancer can damage the glands or their blood supply. It is often temporary (lasting weeks to months) but becomes permanent in a minority of people.
• Autoimmune disease: the immune system attacks the glands, sometimes as part of autoimmune polyglandular syndrome type 1, together with Addison's disease and chronic yeast infections.
• Genetic conditions: including DiGeorge syndrome (22q11.2 deletion), which can cause hypoparathyroidism from birth, and changes in the calcium-sensing receptor gene.
• Low magnesium: severe hypomagnesemia, from alcohol misuse, some medicines (such as long-term proton pump inhibitors) or diarrhea, temporarily stops PTH release. It reverses when magnesium is replaced.
• Rare causes: radiation to the neck, iron or copper overload, and cancer spreading to the glands.

Symptoms

Symptoms come from low calcium (hypocalcemia), which makes nerves and muscles overexcitable:

• Tingling or numbness around the mouth and in the fingers and toes
• Muscle cramps, especially in the legs, feet and hands
• Muscle spasms (tetany), including the hands and wrists bending inward (carpopedal spasm)
• Twitching of the face
• Tiredness, weakness, anxiety, low mood and difficulty concentrating ("brain fog")
• Dry skin, brittle nails and coarse hair
• Seizures in severe cases
• Heart rhythm problems and, rarely, heart failure

Long-term complications

• Cataracts
• Calcium deposits in the brain (basal ganglia)
• Kidney stones, kidney calcification and reduced kidney function, partly from treatment-related high urine calcium
• Dental problems when it starts in childhood

Diagnosis

• Blood calcium: low. Doctors correct for albumin or measure ionized calcium.
• PTH: low or inappropriately normal for the low calcium. This distinguishes it from other causes of low calcium, such as vitamin D deficiency, in which PTH is high.
• Phosphate: high.
• Magnesium, vitamin D levels and kidney function.
• 24-hour urine calcium to guide treatment.
• ECG to check for a prolonged QT interval.
• Genetic or antibody testing when the cause is unclear, especially in children and young adults.
• Bedside signs include Chvostek's sign (tapping the cheek in front of the ear makes the face twitch) and Trousseau's sign (a blood pressure cuff inflated on the arm triggers hand spasm).

Treatment

Emergency treatment

Severe symptoms such as seizures, laryngospasm or heart rhythm problems are treated with intravenous calcium gluconate in hospital, with heart monitoring.

Long-term treatment

• Calcium supplements (calcium carbonate or citrate) several times a day.
• Active vitamin D (calcitriol or alfacalcidol): needed because the kidneys cannot activate vitamin D well without PTH.
• Magnesium if levels are low, and regular vitamin D if deficient.
• Thiazide diuretics in some people to reduce urine calcium.
• PTH replacement therapy: palopegteriparatide, a long-acting form of PTH given by daily injection, is approved in the US for adults with chronic hypoparathyroidism. It can reduce or replace the need for calcium and active vitamin D. Other PTH analogs have been used.

Monitoring

The aim is to keep calcium in the low-normal range, with no symptoms, while avoiding high urine calcium. Blood tests are frequent when treatment starts or changes, then every few months. Kidney function and urine calcium are checked regularly, and kidney imaging is done periodically.

Diet

A diet with adequate calcium from dairy and fortified foods supports treatment. Limiting very high-phosphate foods, such as cola drinks and processed foods with phosphate additives, can help.

Outlook

Temporary hypoparathyroidism after surgery usually recovers within weeks to months. Permanent hypoparathyroidism is lifelong but can be well controlled, allowing most people to live normal lives. Many still notice fatigue or brain fog, which should be discussed with an endocrinologist.

Frequently asked questions

What are the symptoms of hypoparathyroidism?

The main symptoms are tingling around the mouth and in the fingers and toes, muscle cramps and spasms, tiredness and difficulty concentrating. Severe low calcium can cause hand spasms, throat spasm, seizures and heart rhythm problems, which need emergency care.

What causes hypoparathyroidism?

The most common cause is damage to the parathyroid glands during thyroid or other neck surgery. Other causes include autoimmune disease, genetic conditions such as DiGeorge syndrome, severe magnesium deficiency and, rarely, radiation or infiltration of the glands.

Is hypoparathyroidism after thyroid surgery permanent?

Usually not. Most cases after thyroidectomy are temporary and improve within weeks to months as the glands recover. If PTH is still low after about 6 to 12 months, it is considered permanent and needs long-term treatment.

How is hypoparathyroidism treated?

It is treated with calcium supplements and active vitamin D such as calcitriol, plus magnesium if low. Some adults are treated with PTH replacement injections. Severe low calcium needs IV calcium in hospital. Regular blood and urine tests guide the dose.

What is the difference between hypoparathyroidism and hyperparathyroidism?

Hypoparathyroidism means too little parathyroid hormone, causing low calcium with tingling and cramps. Hyperparathyroidism means too much parathyroid hormone, causing high calcium, which can lead to kidney stones, bone loss, tiredness and thirst.