Sorted By Test Name - Mayo Medical Laboratories

PTHRP
81774
recommended. An elevated PTH in the serum could falsely elevate PTH in the washings if the rinse is
contaminated with blood. In these cases, only PTH values significantly higher than the serum should be
considered as true positives. Cytologic examination and measurement of PTH can be performed on the
same specimen. To measure PTH, the fine-needle aspirate (FNA) needle is rinsed with a small volume of
normal saline solution immediately after a specimen for cytological examination has been expelled from
the needle for a smear or CytoTrap preparation. Specimen collection is critical for the performance of the
assay and the needle should be rinsed with a minimal volume. Each FNA needle from a single biopsied
area is washed with 0.1 to 0.5 mL of normal saline. The washes from a single area are pooled (final
volume 1-1.5 mL). PTH levels are measured in the saline wash.
Useful For: An adjunct to cytology examination of fine-needle aspiration specimens to confirm or
exclude presence of parathyroid tissue in the biopsied area
Interpretation: Parathyroid hormone (PTH) values or =100 pg/mL are suggestive of the presence PTH-secreting
tissue at the site biopsied or along the needle track.
Reference Values:
An interpretive report will be provided.
Clinical References: 1. Erbil Y, Salmaslioglu A, Kabul E, et al: Use of preoperative parathyroid
fine-needle asipiration and parathyroid hormone assay in primary hyperparathyroidism with concomitant
thyroid nodules. Am J Surg 2007;193:665-671 2. Owens CL, Rekhtman N, Sokoll L, Ali SZ: Parathyroid
hormone assay in fine-needle aspirate is useful in differentiating inadvertently sampled parathyroid tissue
from thyroid lesions. Diagn Cytopathol 2008 Apr;36(4):227-331 3. Giusti M, Dolcino M, Vera L, et al:
Institutional experience of PTH evaluation on fine-needle washing after aspiration biopsy to locate
hyperfunctioning parathyroid tissue. J Zhejiang Univ Sci B 2009 May;10(5):323-330 4. Kiblut N, Cussac
J, Soudan B, et al: Fine needle aspiration and intraparathyroid intact parathyroid hormone measurement
for reoperative parathyroid surgery. World J Surg 2004 Nov;28(11):1143-1147
Parathyroid Hormone-Related Peptide (PTHrP), Plasma
Clinical Information: Hypercalcemia of malignancy is a common cause of hypercalcemia in
hospitalized patients. Hypercalcemia of malignancy is typically not due to excess parathyroid hormone
(PTH). In these disorders, PTH is usually suppressed due to elevated serum calcium concentrations. A
variety of other mechanisms lead to inappropriate hypercalcemia in hypercalcemia of malignancy. These
include: -Impaired renal function due to a tumor or its treatment -Osteolytic activity within bony
metastases -Release of calcemic cytokines by non-osteolytic bony metastases -Eectopic 1-alpha
hydroxylase activity in tumor tissues -Secretion of humoral factors mimicking PTH action (humoral
hypercalcemia of malignancy [HHM]), usually associated with secretion of parathyroid hormone-related
peptide (PTHrP) by the primary tumor (or more commonly its metastases) -Other, as yet unknown factors
Frequently, a single cause can not be pinpointed. Amongst the defined causes of the condition, PTHrP
secretion is believed to be the most common culprit. PTHrP is a single monomeric peptide that exists in
several isoforms, ranging from approximately 60 amino acids to 173 amino acids in size, which are
created by differential splicing and post-translational processing by prohormone convertases. PTHrP is
produced in low concentrations by virtually all tissues. The physiological role of PTHrP remains
incompletely understood. Its functions can be broadly divided into 4 categories, not all of which are
present in all PTHrP isoforms or in all tissues: -Transepithelial calcium transport, particularly in the
kidney and mammary gland -Smooth muscle relaxation in the uterus, bladder, gastrointestinal tract, and
arterial wall -Regulation of cellular proliferation -Cellular differentiation and apoptosis of multiple tissues
-As an indispensable component of successful pregnancy and fetal development (embryonic gene deletion
is lethal in mammals) PTHrP's diverse functions are mediated through a range of different receptors,
which are activated by different portions of PTHrP. Among the many receptors that respond to PTHrP is
the PTH receptor, courtesy of the fact that 8 of the 13 N-terminal amino acids of PTH and of 3 common
PTHrP isoforms are identical. Since most of PTHrP's actions in normal physiology are autocrine or
paracrine, with circulating levels being very low, this receptor cross-talk only becomes relevant when
there is extreme and sustained over-production of PTHrP. This is seen occasionally in pregnancy,
lactation and, rarely, in a variety of non-malignant diseases. However, most commonly it is observed
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