Primary hyperparathyroidism: laboratory associations and thyroid pathologies
Kemal Agbaht1, Emrah Eraslan2, Ozlem Karaarslan2 & Sevim Gullu1
Background: Diagnosis of primary hyperparathyroidism (PHP) is sometimes challenging and needs supportive evidence. We aimed to document laboratory findings (ratio of calcium clearance to creatinine clearance, ratio of phosphorus clearance to creatinine clearance, serum chloride to phosphorus ratio, serum alkaline phosphatase) and thyroid pathologies associated with established PHP that may provide supplementary clues to the diagnosis.
Methods: We documented all PHP cases diagnosed at our institution during January 2005November 2009. We analysed preoperative calcium, phosphorus, creatinine values (serum and 24-h urine collections), serum albumin, chloride, alkaline phosphatase, 25(OH)D levels, thyroid function and autoantibodies, and thyroid ultrasonography records.
Results: One hundred forty-five (120 (82.8%) women, age 54.1±14.1 years)) PHP cases (94 surgically treated (72 solitary adenomas, 4 cases with double adenomas, 16 hyperplasia, 2 carcinomas) and 51 medically treated) were identified. The ratio of calcium clearance to creatinine clearance was ≥1% in 90.1% of all cases, ratio of phosphorus clearance to creatinine clearance was ≥10% in 96.7% of all cases, chloride to phosphorus ratio was ≥33 in 88% of cases. Serum alkaline phosphatase levels were elevated in only 29 (20%) of all PHP cases, although it correlated well (r:0.608, P<0.001) with parathyroid hormone levels. Thyroid pathology was present in 62.1% cases (Hashimoto thyroiditis 26 (17.9%), Graves Disease 3 (2.1%), euthyroid nodular goiter 53 (36.6%), toxic nodular goiter 6 (4.1%), papillary carcinoma 2 (1.4%) cases).
Discussion: Elevated ratio of calcium clearance to creatinine clearance, ratio of phosphorus clearance to creatinine clearance and serum chloride to phosphorus ratio may support PHP diagnosis. Additionally, thyroid pathologies are present in two third of PHP cases. All these four parameters may be valuable confirmatory practical tests in unsure cases.