Diseases (9)

Overview

Parathyroid hormone (PTH) is a peptide produced by the parathyroid gland. PTH principally serves in the maintenance of calcium homeostasis; thus, assessment of PTH can be an important diagnostic aid for diagnosis of calcium metabolism disorders. In healthy individuals, PTH is secreted from the parathyroid gland as a negative feedback response to circulating calcium ion levels. The half-life of intact PTH is 2 to 5 minutes.

Hypercalcemia may be due to hyperparathyroidism, a group of conditions characterized by an overproduction of PTH. Hyperparathyroidism is separated into primary, secondary, and tertiary causes. Primary hyperparathyroidism is most frequently due to a parathyroid tumor (usually benign) that secretes PTH without feedback control, leading to hypercalcemia, kidney stones, calcium deposits in organs, and decalcification of bone. With primary hyperparathyroidism, patients will generally have high calcium and high PTH levels, while phosphate levels are often low.

Secondary hyperparathyroidism is usually due to kidney failure. In secondary hyperparathyroidism, patients will generally have high PTH levels and low or normal calcium levels. Sometimes, persons with secondary hyperparathyroidism develop high serum calcium and still have high PTH; this is sometimes called tertiary hyperparathyroidism.

Hypocalcemia may be due to hypoparathyroidism or a failure of the parathyroid gland to produce sufficient PTH. Hypoparathyroidism may be due to a variety of conditions and may be persistent, progressive, or transient. Causes include an autoimmune disorder, parathyroid damage or removal during surgery, a genetic condition, and severe illnesses. Affected patients will generally have low PTH levels and low calcium levels and will also have high phosphate levels.

Note: because of the physiological relationship of circulating calcium and PTH, it is always important to interpret PTH results in association with serum calcium.

Clinical Utility

  • Diagnosis of hypercalcemia due to primary hyperparathyroidism related to parathyroid tumors
  • Diagnosis hypercalcemia due to secondary hyperparathyroidism related to kidney disorders, malabsorption, and other calcium metabolic disorders
  • Diagnosis of hypocalcemia due to hypoparathyroidism related to autoimmune disorders, injuries, surgery, and other related disorders

Interpretation

Increased in:

  • Primary hyperparathyroidism
  • Secondary hyperparathyroidism due to renal disease
  • Pseudohypoparathyroidism, Types I and II
  • Pseudo-idiopathic Hypoparathyroidism
  • Rickets
  • Osteomalacia
  • Vitamin D deficiency
  • Some drugs: Anticonvulsants, furosemide, propofol, phosphates

Decreased in:

  • Hypercalcemic states other than primary hyperparathyroidism
  • Hypoparathyroidism
  • Parathyroidectomy
  • Thyroid Surgery, some
  • Autoimmune Hypoparathyroidism
  • Sarcoidosis
  • Hyperthyroidism
  • Hypomagnesemia
  • Malignancy with hypercalcemia
  • Nonparathyroid hypercalcemia

Reference Ranges

  pg/ml ng/L
C-terminal &    
midmolecule    
Serum    
1-16 yr:  51-217  51-217
Adults:  50-330  50-330
Plasma (EDTA):    
     
N-Terminal:    
Serum    
2-13 yr:  14-21  14-21
Adult: 8-24  8-24
Intact molecule:    
Serum    
Cord:     
2-20 yr: 9-52  9-52
Adults:  10-65  10-65
Plasma (EDTA): 1.0-5.0 pmol/L  


 

 

Methodology

Chemiluminescent enzyme-labeled immunometric assay, ELISA.

Specimen Collection

Serum (SST) or Plasma EDTA (Lavender)

Fasting morning specimen preferred.
Place on ice; refrigerate during centrifugation, and freeze immediately.

Stability:

  • Store Frozen at -20 to -70°C

Additional Testing

Comprehensive Metabolic Panel (see CMP for listed tests), Calcitonin, Albumin, Creatinine, Phosphorous, Calcium, Magnesium, Vitamin D-25-Hydroxy, Thyroid Stimulating Hormone, Ellsworth-Howard test.

Turnaround Time

1-3 days.

CPT

83970

LOINC

ICD10

C41Malignant neoplasm of bone and articular cartilage of other and unspecified sites
C41.9Malignant neoplasm of bone and articular cartilage, unspecified
C74Malignant neoplasm of adrenal gland
C74.0Malignant neoplasm of cortex of adrenal gland
C74.1Malignant neoplasm of medulla of adrenal gland
C74.9Malignant neoplasm of unspecified part of adrenal gland
C74.90Malignant neoplasm of unspecified part of unspecified adrenal gland
C74.91Malignant neoplasm of unspecified part of right adrenal gland
C74.92Malignant neoplasm of unspecified part of left adrenal gland
E04.1Nontoxic single thyroid nodule
E04.2Nontoxic multinodular goiter
E05.1Thyrotoxicosis with toxic single thyroid nodule
E05.2Thyrotoxicosis with toxic multinodular goiter
E25Adrenogenital disorders
E25.0Congenital adrenogenital disorders associated with enzyme deficiency
E25.8Other adrenogenital disorders
E25.9Adrenogenital disorder, unspecified
E55Vitamin D deficiency
E55.0Rickets, active
E55.9Vitamin D deficiency, unspecified
I10Essential (primary) hypertension
I95.0Idiopathic hypotension
I99Other and unspecified disorders of circulatory system
M83Adult osteomalacia
M83.2Adult osteomalacia due to malabsorption
M83.5Other drug-induced osteomalacia in adults
M83.8Other adult osteomalacia
M83.9Adult osteomalacia, unspecified
M87Osteonecrosis
M89Other disorders of bone
Q78.2Osteopetrosis

References