Note: UCLA Endocrine Surgery and the Association of Endocrine Surgeons are both excellent sources of information for learning about the various reasons calcium may be high. As primary hyperparathyroid disease is the most common cause of high blood calcium, and that was our experience, Parathyroid Peeps is only addressing this causation.
Primary hyperparathyroidism is diagnosed biochemically, through blood tests. These tests include serum calcium, PTH (parathyroid hormone), and vitamin D-25. Most patients present classically with:
- High serum calcium (normal = 8.7 – 10.1 mg/dl)
- High PTH (normal = 15 – 65 pg/ml)
- Low vitamin D-25 (normal = 30 – 100 ng/ml)
*Note that normal lab ranges may vary from lab to lab.
According to the experts at the Norman Parathyroid Center (NPC), persistent calcium levels 10.1 and above (in an adult) is almost always a parathyroid tumor. Approximately 20-25 percent of cases don’t present classically. Normohormonal primary hyperparathyroidism occurs when calcium is high, but PTH is still within the normal range. Normocalcemic primary hyperparathyroidism occurs when calcium is in the normal range, but PTH is elevated. Additional lab tests including ionized calcium and urine calcium may be helpful in making the diagnosis when the presentation is not classic.
Dr. Norman from NPC recently posted on Parathyroid Disease Awareness, that
PTH levels do not have to be high to diagnose primary hyperparathyroidism. Almost 20% of people with a large parathyroid tumor will have all normal PTH levels. Another 30% have PTH levels that are mildly elevated sometimes and normal sometimes. Another 20% will have only mildly elevated PTH levels. It is a minority of patients who have high calcium and high PTH levels at the same time. If you have high calcium and PTH levels at the same time, then you have had a parathyroid tumor for six or seven years before somebody figured it out. The concept that you need both high calcium and parathyroid hormone levels to make this diagnosis is incorrect. High calcium levels by itself assures the diagnosis at least 99% of the time. PTH levels add almost nothing to it.
According to Lab Tests Online.org, a peer reviewed, public resource on clinical testing that is a result of a collaboration of professional societies representing the laboratory community,
“When an abnormal total calcium result is obtained, it is viewed as an indicator of an underlying problem. To help diagnose the underlying problem, additional tests are often done to measure ionized calcium, urine calcium, phosphorous, magnesium, vitamin D, parathyroid hormone (PTH) and PTH-related peptide (PTHrP). Both PTH and vitamin D are responsible for maintaining calcium concentrations in the blood within a narrow range of values.
If the calcium is abnormal, measuring calcium and PTH together can help determine whether the parathyroid glands are functioning normally. Measuring urine calcium can help determine whether the kidneys are excreting the proper amount of calcium, and testing for vitamin D, phosphorus, and/or magnesium can help determine whether other deficiencies or excesses exist. Frequently, the balance among these different substances (and the changes in them) is just as important as the concentrations.
Total calcium level is often measured as part of a routine health screening as it is included in the comprehensive metabolic panel (CMP) and the basic metabolic panel (BMP). Check that yours is in the tight range that is normal. When parathyroid disease is suspect, Ionized Calcium is considered by experts to be the “gold standard” for rechecking calcium levels. Parathyroid Hormone (PTH) levels are not generally tested unless calcium is found to be high. A problem however, is that doctors often do not order a PTH test or understand the relationship of Vitamin D to Calcium when a patient has primary hyperparathyroid disease. Therefore it may be necessary for patients to request that their PTH and vitamin D be tested.
“Normal” Lab Values
It is our understanding that normal ranges posted on the lab reports may vary slightly among different laboratories. It is important for patients to understand that many labs may not correct the calcium range for the patient’s age. Teenagers and people in their early 20’s can have calcium levels up to 10.7 mg/dl. However, once you are over 30 you should have all calcium levels in the 9’s with the upper limit of normal being 10.0 or 10.1 mg/dl. An adult with calcium levels in the 10’s is very likely to have a parathyroid tumor. Unfortunately, most doctors don’t understand that calcium levels change with age, so they are often confused on this issue. We hope this information is useful when you discuss your lab values with your physician(s).
The CalciumPro app available from the Norman Parathyroid Center which can be downloaded onto an iPhone, iPad or Android, can be a helpful tool to assist in diagnosing this disease. By entering your blood calcium, PTH as well as your vitamin D levels from copies of lab results ordered by your physician that you have requested copies of, you will get a visual image of your chances of having this disease (from very unlikely, unlikely, possible, likely to very likely). The app will also show you your risks for other diseases like osteoporosis, kidney stones, heart disease, heart rhythm problems, certain cancers, and high blood pressure.
To identify the source of the excessive hormone secretion, medical imaging is often performed. There are very different opinions as to the effectiveness and usefulness of imaging as a diagnostic tool. Diagnosis and/or referrals for surgery however are often delayed due to the lack of a visual confirmation of an adenoma resulting from scans. In our experience, a scan was not required prior to being diagnosed and accepted for surgery.