Secondary Hyperparathyroidism (SHPT)

Most people are born with four parathyroid glands. They are very small, about the size of a pea. They sit in your neck, close to your thyroid. These glands make parathyroid hormone (PTH), a natural chemical messenger that helps control the levels of calcium and phosphorus in your blood. If calcium and phosphorus levels are not balanced, your body makes more PTH to try to fix the problem.

People living with chronic kidney disease (CKD), especially those on dialysis, often have trouble keeping calcium and phosphorus in balance. When this happens, the body may make too much PTH. A high PTH level is also called hyperparathyroidism. Over time, too much PTH can weaken your bones and harm your blood vessels and heart.

Most people with secondary hyperparathyroidism (SHPT) do not have symptoms at first. It is more common to find SHPT from blood tests, not symptoms. 

If you do have symptoms, you may notice:

• Bone or joint pain
• Tingling around the mouth
• Pins and needles, numbness, or tingling in your fingers or toes
• Weak bones that break easily
• Muscle cramps or weakness
• Kidney stones
• Pruritis (itchy skin)
• Feeling very tired
• Heart problems

In children, symptoms may show up sooner. This is because their bones are still growing. Symptoms more common in children include not growing as expected (also known as growth faltering) or weak bones that break easily.

SHPT happens mostly because of CKD. The risk is higher in later stages of CKD, and highest in people with kidney failure who are on dialysis. When your kidneys are damaged, they cannot:

• remove extra phosphorus well. This can cause high phosphorus levels in your blood.
• keep calcium levels in a healthy range, leading to hypocalcemia (low blood calcium level)
• make enough active vitamin D, which helps control calcium

Less common causes of SHPT include: 

• Very low vitamin D levels (not enough vitamin D in your body)
• Not getting enough calcium from your diet
• Digestive problems or stomach surgery, such as celiac disease, Crohn’s disease, or gastric bypass surgery

These conditions can affect how your body absorbs calcium and vitamin D. When this happens, your body may make more PTH to try to keep calcium levels balanced.

There are three main types of hyperparathyroidism:

1. Primary: the problem is in the parathyroid glands, like a benign (non-cancerous) tumor
2. Secondary: the problem is caused by another condition in your body, most often CKD
3. Tertiary: parathyroid glands stay overactive even after kidney problems improve (for example, after a transplant)

Over time, making too much PTH is not healthy and can lead to problems with your bones, blood vessels, and heart. If not treated, SHPT can lead to:

• Mineral and bone disorder (CKD-MBD)
• Broken bones (fractures)
• Calcium buildup in your blood vessels (also known as calcifications)
• Heart and blood vessel problems 
• Problems with blood flow
• Anemia
• Calciphylaxis (kal-suh-fuh-LAK-suhs) - a rare but very serious condition that causes painful skin sores and can raise your risk of sepsis (severe infection) and death

Tests

Your healthcare team may order blood tests to check your levels of:

• Parathyroid hormone (PTH) (sometimes called “intact PTH” or “iPTH”)
• Calcium
• Phosphorus
• Vitamin D

You may also have imaging tests, such as an X-ray, bone density scan (DEXA), echocardiogram (ECHO), ultrasound, or CT scan. These tests can help show how strong your bones are, whether calcium is building up in your heart or blood vessels, and the size of your parathyroid glands. In rare cases, a bone biopsy may be needed. This is when a small piece of bone is removed and looked at under a microscope.