Serum PTH reference values in an adult Brazilian population: implications for the diagnosis of hyperparathyroidism.
ARCHIVES OF ENDOCRINOLOGY AND METABOLISM 2019;
63:182-185. [PMID:
30916167 PMCID:
PMC10522136 DOI:
10.20945/2359-3997000000117]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 01/16/2019] [Indexed: 11/23/2022]
Abstract
OBJECTIVE
To define serum parathyroid hormone (PTH) reference values in carefully selected subjects following the recommended pre-analytical guidelines.
SUBJECTS AND METHODS
First, 676 adults who would be submitted to thyroidectomy were evaluated. Patients using interfering medications or with malabsorption syndrome, hypomagnesemia, hyper- or hypophosphatemia, hypo- or hypercalcemia, 25-hydroxyvitamin D < 30 ng/dL, estimated glomerular filtration rate < 60 mL/min/1.73 m2, urinary calcium/creatinine ratio ≥ 0.25, thyroid dysfunction, parathyroid adenoma detected during surgery were excluded. The sample consisted of 312 subjects.
RESULTS
The median, minimum, maximum, and 2.5th and 97.5th percentiles of the PTH values obtained were 30, 7.2, 78, 10.1, and 52 pg/mL, respectively. Thus, the reference range was 10 to 52 pg/mL. PTH > 65 pg/mL, the upper limit of normal according to the manufacturer of the kit, was observed in only one subject (0.3%). Considering the upper limit proposed by the kit's manufacturer, 1/6 hypercalcemic patients and 4/8 normocalcemic patients with PHPT had normal PTH. Using the upper limit established in this study, only one normocalcemic patient had normal PTH. Thus, the sensitivity of PTH in detecting asymptomatic primary hyperparathyroidism (PHPT) using the values recommended by the kit and established in this study was 64% and 93%, respectively (50% versus 87.5% for normocalcemic PHPT).
CONCLUSION
The upper reference limit of PTH obtained for a rigorously selected sample was 20% lower than that provided by the assay, which increased its sensitivity in detecting PHPT.
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