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- 1 What causes very high blood calcium levels
- 2 How can doctors tell parathyroid vs cancer causes of hypercalcemia?
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How can doctors tell parathyroid vs cancer causes of hypercalcemia?
The key test is the serum PTH level — it tells you which fork in the road to take.
Doctors start by measuring serum calcium and intact PTH together. In primary hyperparathyroidism, PTH is elevated or inappropriately normal for the calcium level. In malignancy, the hypercalcemia is driven by PTH-related peptide (PTHrP) or other factors, so PTH is suppressed — low or low-normal [7, 9, 11]. One study of 104 hypercalcemic patients found that a PTH cutoff of 26 ng/L had 95% specificity for detecting malignancy, meaning a low PTH strongly points away from parathyroid disease [7].
When PTH is low, the next step is to measure PTHrP. Elevated PTHrP confirms humoral hypercalcemia of malignancy [7, 9, 10, 12]. Cancers that commonly produce PTHrP include squamous cell lung cancer, head and neck cancers, bladder cancer, ovarian cancer, and penile cancer [4, 5, 10, 12]. Some lymphomas and granulomatous diseases cause hypercalcemia through excess 1,25-dihydroxyvitamin D instead [6, 8].
A few cases are tricky. Rarely, a patient can have both primary hyperparathyroidism and malignancy at the same time, with elevated PTH and elevated PTHrP [3, 8]. And some parathyroid adenomas produce only mildly elevated PTH that falls in the low-normal range, which can cause confusion [1].
The calcium/creatinine clearance ratio helps separate primary hyperparathyroidism from familial hypocalciuric hypercalcemia (FHH), a benign condition that does not need surgery. In FHH, the ratio is below 0.01; in primary hyperparathyroidism, it is above 0.02 [2].
| Test | Primary hyperparathyroidism | Malignancy | FHH |
|---|---|---|---|
| Serum PTH | Elevated or inappropriately normal | Suppressed (low/low-normal) | Normal to mildly elevated |
| PTHrP | Normal | Elevated | Normal |
| Calcium/creatinine clearance ratio | >0.02 | Variable | <0.01 |
| 24-hour urine calcium | High | Variable | Low |
My call: the diagnostic sequence is straightforward — measure PTH first, then PTHrP if PTH is low, and use the calcium clearance ratio to rule out FHH. Confidence: high.
Sources used 12
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Hypercalcemia with low-normal serum intact PTH: A novel presentation of primary hyperparathyroidism
This case report presents a unique instance of primary hyperparathyroidism in a patient with hypercalcemia and low-normal serum intact parathyroid hormone (PTH) levels, challenging the traditional diagnostic criteria for the condition.
DOI: 10.1016/0002-9343(91)90193-2 -
Plasma 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and parathyroid hormone in familial hypocalciuric hypercalcemia and primary hyperparathyroidism
This study compares plasma levels of 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and parathyroid hormone in patients with familial hypocalciuric hypercalcemia and primary hyperparathyroidism, revealing significant differences in vitamin D metabolism and parathyroid hormone lev…
DOI: 10.1530/EJE-08-0440 -
Concomitant Primary Hyperparathyroidism in Patients with Multiple Myeloma: A Possible Link?
This study describes four cases of active multiple myeloma with hypercalcemia and concomitant primary hyperparathyroidism, showing lack of PTHR1 in MM cells and proposing a paracrine role for PTH in MM bone disease and potential links between PHPT and MM that warrant further inv…
DOI: 10.1159/000509768 -
Primary Hyperparathyroidism and Pancreatitis: A Rare Association with Multiple Facets
This study presents five cases of primary hyperparathyroidism (PHPT) revealed by acute pancreatitis, highlighting the association between hypercalcemia and pancreatitis, and the favorable outcomes following surgical intervention in most patients.
DOI: 10.1155/2016/7294274 -
Spontaneous Hemorrhage of A Parathyroid Adenoma Into the Mediastinum
A rare case report describing spontaneous extracapsular hemorrhage of a parathyroid adenoma presenting with acute neck pain and dysphagia in a 56-year-old woman, successfully treated by surgical excision with normalization of calcium and parathyroid hormone levels.
DOI: 10.4158/ep11329.cr -
A Case of Primary Hyperparathyroidism Due to an Oxyphil Cell Adenoma.
This study presents the first reported case in Japan of primary hyperparathyroidism caused by a functioning oxyphil cell adenoma, characterized by histological, immunohistochemical, and ultrastructural evidence, along with the presence of lymphangiectasia.
DOI: 10.1507/endocrj1954.39.499 -
The clinical utility of parathyroid hormone-related peptide in the assessment of hypercalcemia
A retrospective UNC-based study evaluating whether a PTH cutoff can guide PTHrP testing in hypercalcemic patients, finding low sensitivity but high specificity for PTHrP in detecting hypercalcemia of malignancy and supporting a strategy to measure PTH first and limit PTHrP testi…
DOI: 10.1016/j.cca.2008.12.040 -
Refractory Hypercalcemia in Squamous Cell Carcinoma of the Esophagus—a Case Report and Review of Literature
This case report presents a unique instance of refractory hypercalcemia in a patient with metastatic squamous cell carcinoma of the esophagus, characterized by elevated serum levels of both parathyroid hormone (PTH) and parathyroid hormone-related peptide (PTHrP), suggesting a c…
DOI: 10.1007/s12029-018-0124-1 -
Cinacalcet for Hypercalcemia Caused by Pulmonary Squamous Cell Carcinoma Producing Parathyroid Hormone-Related Peptide
This case study explores the efficacy of cinacalcet in treating severe hypercalcemia caused by a parathyroid hormone-related peptide-producing squamous cell lung carcinoma, suggesting its potential value in managing this condition.
DOI: 10.1159/000335676 -
Ovarian carcinoma producing parathyroid hormone-related protein causing hypercalcemia and metastatic calcification detected on 18 F-FDG PET-CT
This study presents two cases of ovarian carcinoma associated with hypercalcemia and metastatic calcification, detected through 18 F-FDG PET-CT, highlighting the role of parathyroid hormone-related protein (PTHrP) in these conditions.
DOI: 10.4103/0972-3919.121973 -
Hypercalcemia associated with early recurrence of vulvar cancer
This study presents a case of a 65-year-old woman with vulvar cancer who developed hypercalcemia as a paraneoplastic syndrome due to early recurrence of the disease, highlighting the rare association between vulvar cancer and hypercalcemia.
DOI: 10.1007/s00404-009-1075-3 -
PARATHYROID HORMONE RELATED PROTEIN PRODUCING PENILE CANCER
This case report documents a 53-year-old man with advanced penile squamous cell carcinoma associated with humoral hypercalcemia of malignancy due to parathyroid hormone-related protein production, confirmed by immunohistochemistry.
DOI: 10.1016/s0022-5347(05)65428-6