CDC73 Genotype

Most people never think about their parathyroid glands, four tiny glands in the neck that quietly manage calcium. But if a specific inherited gene change runs in your family, those glands can start growing tumors decades earlier than expected, and in a small share of cases the growths turn cancerous.

This test reads the gene that normally guards against that scenario. A single result tells you whether you carry an inherited change that raises your lifetime risk of overactive parathyroid glands and a rare parathyroid cancer, something a one-time calcium check cannot tell you.

What This Gene Does

CDC73 (cell division cycle 73), once called HRPT2, carries the instructions for a protein called parafibromin. Parafibromin works inside the cell nucleus as a brake on unchecked growth, the kind of protein scientists call a tumor suppressor. When both working copies of the gene are lost inside a cell, that brake fails and a tumor can form.

People who inherit one damaged copy of this gene start life already halfway to that failure. Every cell carries the single inherited change, and a tumor forms when a cell happens to lose its one remaining good copy. This is why carriers can develop parathyroid problems much younger than the general population.

Overactive Parathyroid Glands

The most common consequence of carrying an inherited change here is primary hyperparathyroidism, a condition where the parathyroid glands pump out too much hormone and drive blood calcium up. In one large study of carriers, about 2 in 3 developed primary hyperparathyroidism by age 50, rising to roughly 3 in 4 by age 70. Onset often comes in adolescence or early adulthood rather than later life.

Carriers also tend to present with more severe biochemical disease than people with ordinary sporadic hyperparathyroidism. That matters because high calcium over time damages bones and kidneys, and knowing you carry the change lets you catch the process early rather than after complications appear.

Parathyroid Cancer Risk

Parathyroid cancer is rare in the general population, but this gene is the single most important driver of it. Across synthesized carrier data, roughly 10 to 15 percent of people with an inherited change in this gene develop parathyroid carcinoma over their lifetime, and some cohorts report figures as high as 30 percent, a risk far above baseline.

The connection runs in the other direction too. Among people who develop what looks like sporadic parathyroid cancer with no family history, about 1 in 4 turn out to carry an inherited change in this gene. Finding it changes their surveillance and flags relatives who may share the same hidden risk.

In people who already have parathyroid cancer, changes in this gene also track with worse behavior. In one tumor study, loss of the parafibromin protein was linked to about 4 times the risk of the cancer spreading, and finding a mutation in the gene itself was linked to about 7 times the risk. A later pooled analysis confirmed the link with parafibromin loss but did not find the gene mutation itself to be a statistically significant predictor. These are prognostic signals in diagnosed disease, not predictions for a healthy carrier.

Jaw, Kidney, and Uterine Tumors

Inherited changes in this gene cause a broader inherited condition called hyperparathyroidism-jaw tumor syndrome. Beyond the parathyroid glands, carriers can develop bony tumors of the jaw, cysts and tumors in the kidneys, and tumors of the uterus, some of which can be malignant.

Not every carrier develops every feature, and the absence of jaw tumors does not rule out the inherited condition. Many affected families look like simple familial hyperparathyroidism, with high calcium as the only visible sign. A positive result is what tells you the wider spectrum is possible and worth watching for.

How Variant Type Shapes Risk

Not all inherited changes in this gene carry the same weight. The clearest pattern from carrier data is that high-impact changes, the kind that cut the protein short or scramble how it is made, carry more cancer risk than subtler single-letter substitutions. In a cohort study of 419 individuals, high-impact changes were linked to about 6.6 times the risk of parathyroid cancer compared with lower-impact changes.

That same study found the risk of developing hyperparathyroidism at all was similar across variant types. The variant class mainly shaped whether the disease turned malignant, not whether it appeared. The extra risk was tied specifically to damage to one end of the protein, its C-terminal region. This is why the exact change you carry, not just a positive or negative call, shapes what your doctor should watch for.

A Result You Only Need Once

This is a fixed genetic result. Your genotype does not change over your lifetime, so unlike a cholesterol or calcium level, there is no trend to track and no reason to repeat the genetic test itself once you have a confident answer.

The value of the result is not in retesting the gene, it is in what you monitor afterward. If you carry a change, the tests that need regular tracking are your blood calcium and parathyroid hormone, ideally at least once a year and often starting in childhood in affected families. That ongoing surveillance is what catches a growing tumor early, while the genotype simply tells you to start.

What to Do With a Positive Result

A positive result is a starting point, not a diagnosis. The first step is usually to confirm the specific change, understand its variant class, and pair it with your calcium and parathyroid hormone levels to see whether disease is already present. If a chip-based or panel test flagged the change, a confirmatory method may be warranted before acting on it.

The right specialists to involve are an endocrinologist and a genetic counselor, who can build a surveillance plan for the parathyroid glands and screen for jaw, kidney, and uterine involvement. Because this is inherited, a positive result also has direct implications for your biological parents, siblings, and children, who each have a meaningful chance of carrying the same change and may benefit from their own testing.

Why a Negative Result Is Not Always the Full Story

The most important caveat is coverage. Standard sequencing reads the letters of the gene, but it can miss large missing chunks of it. In one national cohort, these large deletions accounted for 35 percent of people who actually carried a disease-causing change, and they were found only when doctors specifically looked for missing segments after ordinary sequencing came back negative.

• Panel coverage: a test only detects the variants it is designed to find, so a negative sequencing result does not rule out a large deletion or a rare change the assay does not cover.
• Variants of uncertain meaning: some changes, including deep splice-site changes, are initially labeled uncertain and later reclassified as harmful once additional testing clarifies their effect.
• Ancestry differences: the specific changes seen in this gene vary between populations, so interpretation depends partly on your genetic background.
• Clinical-grade versus consumer testing: a direct-to-consumer report covering this region is not equivalent to clinical-grade analysis and should not be treated as a definitive result.

If your personal or family history strongly suggests this inherited condition but sequencing is negative, the workup is not over. Deletion testing and RNA-based analysis can uncover changes that routine sequencing misses, which is exactly why interpretation belongs with a genetics or endocrine specialist rather than a single lab printout.