{"id":4422021,"date":"2024-12-31T11:36:42","date_gmt":"2024-12-31T17:36:42","guid":{"rendered":"https:\/\/myendoconsult.com\/learn\/?p=4422021"},"modified":"2024-12-31T11:38:46","modified_gmt":"2024-12-31T17:38:46","slug":"normal-pth-levels-by-age","status":"publish","type":"post","link":"https:\/\/myendoconsult.com\/learn\/normal-pth-levels-by-age\/","title":{"rendered":"Normal PTH levels by Age"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\"><strong>Parathyroid Hormone (PTH) Blood Test<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Parathyroid hormone (PTH) is an <strong>84\u2013amino-acid peptide<\/strong> secreted predominantly by <strong>two pairs of parathyroid glands<\/strong>, located behind or adjacent to the thyroid gland in the neck. Occasionally, ectopic <a href=\"https:\/\/myendoconsult.com\/learn\/anatomy-of-the-parathyroid-gland\/\"  data-wpil-monitor-id=\"25\">parathyroid glands<\/a> may be found along their developmental route from the mediastinum to the neck. The 84-amino-acid PTH is packaged into <strong>dense secretory granules<\/strong> for regulated secretion.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"960\" height=\"672\" src=\"https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/PTH-Molecule.png\" alt=\"\" class=\"wp-image-4422027\" srcset=\"https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/PTH-Molecule.png 960w, https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/PTH-Molecule-300x210.png 300w, https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/PTH-Molecule-768x538.png 768w\" sizes=\"auto, (max-width: 960px) 100vw, 960px\" \/><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Figure 1. Structure of <a href=\"https:\/\/myendoconsult.com\/learn\/parathyroid-hormone-action-a-comprehensive-review\/\"  data-wpil-monitor-id=\"26\">Parathyroid hormone<\/a> (1-84)<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Clinically, <strong>measurement of PTH in serum or plasma<\/strong> is vital for the <strong>evaluation and management<\/strong> of:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Thyroid disorders<\/strong> (e.g., in the context of thyroid surgery),<\/li>\n\n\n\n<li><strong>Kidney disorders<\/strong> (particularly chronic renal failure [CRF] and secondary Hyperparathyroidism),<\/li>\n\n\n\n<li><strong>Various causes of hyper- or hypocalcemia<\/strong> (to differentiate parathyroid vs. nonparathyroid etiologies).<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Since <strong>PTH<\/strong> directly influences <strong>calcium and phosphate<\/strong> homeostasis, this assay is <strong>routinely monitored<\/strong> in patients with <strong>chronic renal failure<\/strong> and in suspected or established <strong>primary Hyperparathyroidism<\/strong>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Reference Ranges<\/strong> of PTH by Age<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Because PTH assays measure <strong>different fragments<\/strong> of the hormone (or the intact molecule), reference ranges may <strong>vary<\/strong> based on the methodology. Standard reported ranges include:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Adults (Serum)<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>C-terminal <\/strong>: 50\u2013330 pg\/mL (50\u2013330 ng\/L)<\/li>\n\n\n\n<li><strong>N-terminal<\/strong>: 8\u201324 pg\/mL (8\u201324 ng\/L)<\/li>\n\n\n\n<li><strong>Intact PTH<\/strong>: 10\u201365 pg\/mL (10\u201365 ng\/L)<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Adults (Plasma)<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>C-terminal <\/strong>: &lt;50 microLEq\/mL (&lt;50 mLEq\/L)<\/li>\n\n\n\n<li><strong>N-terminal<\/strong>: &lt;6.1 pmol\/L<\/li>\n\n\n\n<li><strong>Intact PTH<\/strong>: 1\u20135 pmol\/L<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Pediatrics<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>C-terminal <\/strong>(ages 1\u201316): 51\u2013217 pg\/mL (51\u2013217 ng\/L)<\/li>\n\n\n\n<li><strong>N-terminal<\/strong> (ages 2\u201313): 14\u201321 pg\/mL (14\u201321 ng\/L)<\/li>\n\n\n\n<li><strong>Intact PTH<\/strong> (ages 2\u201320): 9\u201352 pg\/mL (9\u201352 ng\/L)<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">Table 1. Laboratory ranges for fractions of the PTH molecule<\/p>\n\n\n\n<table id=\"tablepress-137\" class=\"tablepress tablepress-id-137\">\n<thead>\n<tr class=\"row-1\">\n\t<th class=\"column-1\"><strong><\/strong><\/th><td class=\"column-2\"><\/td><td class=\"column-3\"><\/td><td class=\"column-4\"><\/td>\n<\/tr>\n<\/thead>\n<tbody class=\"row-striping row-hover\">\n<tr class=\"row-2\">\n\t<td class=\"column-1\"><\/td><td class=\"column-2\"><\/td><td class=\"column-3\"><\/td><td class=\"column-4\"><\/td>\n<\/tr>\n<tr class=\"row-3\">\n\t<td class=\"column-1\"><strong>Assay<\/strong><\/td><td class=\"column-2\"><strong>Assay Includes<\/strong><\/td><td class=\"column-3\"><strong>Conventional Normal Values (pg\/mL)<\/strong><\/td><td class=\"column-4\"><strong>SI Units (ng\/L)<\/strong><\/td>\n<\/tr>\n<tr class=\"row-4\">\n\t<td class=\"column-1\">PTH Intact (whole)<\/td><td class=\"column-2\">Intact PTH<\/td><td class=\"column-3\">10\u201365<\/td><td class=\"column-4\">10\u201365<\/td>\n<\/tr>\n<tr class=\"row-5\">\n\t<td class=\"column-1\">PTH N-terminal<\/td><td class=\"column-2\">N-terminal<\/td><td class=\"column-3\">8\u201324<\/td><td class=\"column-4\">8\u201324<\/td>\n<\/tr>\n<tr class=\"row-6\">\n\t<td class=\"column-1\">PTH C-terminal<\/td><td class=\"column-2\">C-terminal<\/td><td class=\"column-3\">50\u2013330<\/td><td class=\"column-4\">50\u2013330<\/td>\n<\/tr>\n<tr class=\"row-7\">\n\t<td class=\"column-1\">Midmolecule<\/td><td class=\"column-2\">Midregion<\/td><td class=\"column-3\">Not routinely measured<\/td><td class=\"column-4\">Not routinely measured<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<!-- #tablepress-137 from cache -->\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Physiology and Secretory Regulation of PTH<\/strong><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Parathyroid Glands and PTH Synthesis<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>PTH is synthesized as a <strong>115-amino-acid pre-pro-peptide<\/strong> but <strong>84\u2013amino-acid PTH<\/strong> is the primary secreted form.<\/li>\n\n\n\n<li>The <strong>major regulatory signal<\/strong> for PTH secretion is <strong>serum calcium<\/strong>. When <strong>ionized calcium<\/strong> rises, PTH secretion <strong>falls<\/strong>. When calcium levels drop, PTH levels <strong>increase<\/strong>.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Calcium-Sensing Receptor (CaSR)<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The <strong>parathyroid glands<\/strong> express a <strong>cell-surface calcium-sensing receptor (CaSR)<\/strong>, which detects extracellular calcium.<\/li>\n\n\n\n<li><strong>Gain-of-function mutations<\/strong> of the CaSR can lead to <strong>autosomal dominant hypocalcemia (ADH)<\/strong>, while <strong>loss-of-function<\/strong> mutations cause <strong>familial hypocalciuric hypercalcemia (FHH)<\/strong>.<\/li>\n\n\n\n<li><strong>Calcimimetics<\/strong> (e.g., cinacalcet, etelcalcetide) activate the CaSR to reduce PTH secretion, useful in secondary Hyperparathyroidism (CKD) and certain severe <a href=\"https:\/\/myendoconsult.com\/learn\/primary-hyperparathyroidism-a-comprehensive-guide-for-patients\/\"  data-wpil-monitor-id=\"27\">primary hyperparathyroid<\/a> cases.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Magnesium and Vitamin D Impact<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Magnesium<\/strong> also plays a role: severe or prolonged hypomagnesemia can <strong>blunt<\/strong> PTH secretion.<\/li>\n\n\n\n<li><strong>1,25-Dihydroxyvitamin D (1,25-D)<\/strong> also <strong>inhibits<\/strong> PTH gene transcription.<\/li>\n\n\n\n<li>Serum phosphate may <strong>directly<\/strong> or <strong>indirectly<\/strong> modulate PTH, although data are somewhat mixed.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Metabolism and Clearance of PTH<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>PTH<\/strong> has a <strong>circulating half-life<\/strong> of about <strong>&lt;5 minutes<\/strong>.<\/li>\n\n\n\n<li>Hormone fragments (N-terminal, midregion, C-terminal) are produced mainly in the <strong>liver<\/strong> and <strong>kidney<\/strong>.<\/li>\n\n\n\n<li><strong>C-terminal<\/strong> fragments are cleared by <strong>glomerular filtration<\/strong>, so they <strong>accumulate in renal failure<\/strong>.<\/li>\n\n\n\n<li>Only the <strong>amino terminus<\/strong> (PTH 1\u201334) has <strong>full biological<\/strong> activity.<\/li>\n\n\n\n<li><strong>Intact PTH<\/strong> assays measure PTH 1\u201384 plus certain fragments (e.g., 7\u201384). \u201cWhole\u201d or \u201cbio-intact\u201d assays aim to detect only <strong>PTH 1\u201384<\/strong>, but many labs still use the <strong>intact PTH<\/strong> test.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Biologic Effects of PTH<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Bone<\/strong>: In high levels (as in Hyperparathyroidism), PTH <strong>increases osteoclastic bone resorption<\/strong>. Intermittent low-dose PTH can <strong>increase osteoblastic bone formation<\/strong> (used therapeutically for osteoporosis, e.g., teriparatide).<\/li>\n\n\n\n<li><strong>Kidney<\/strong>: PTH <strong>increases calcium reabsorption<\/strong> in the distal tubule and <strong>decreases phosphate reabsorption<\/strong> in the proximal tubule, contributing to <strong>hypercalcemia<\/strong> and <strong>hypophosphatemia<\/strong>.<\/li>\n\n\n\n<li><strong>Intestine<\/strong>: PTH indirectly <strong>enhances calcium<\/strong> and <strong>phosphate<\/strong> absorption <strong>via<\/strong> increased renal synthesis of <strong>1,25-dihydroxyvitamin D<\/strong>.<\/li>\n\n\n\n<li><strong>Major Receptor<\/strong>: PTH\/PTHrP receptor, activating cAMP and phospholipase C pathways.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Indications &amp; Uses<\/strong><\/h2>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Parathyroidectomy for Primary Hyperparathyroidism<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Intraoperative PTH monitoring<\/strong>: a drop of >50% post-resection suggests surgical success.<\/li>\n\n\n\n<li><strong>Long-term cure<\/strong> is also linked to normal serum calcium (&lt;10.2 mg\/dL) within six months after surgery.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Hypocalcemia Secondary to Thyroidectomy<\/strong>\n<ul class=\"wp-block-list\">\n<li>A <strong>single intraoperative or postoperative<\/strong> intact PTH measurement can predict development of symptomatic hypocalcemia and guide <strong>vitamin D supplementation<\/strong>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Suspected Hypercalcemia due to Hyperparathyroidism<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Mild hypercalcemia<\/strong> + <strong>high-normal or elevated PTH<\/strong> suggests primary Hyperparathyroidism.<\/li>\n\n\n\n<li><strong>Decreased PTH<\/strong> is typical in <strong>nonparathyroid hypercalcemic disorders<\/strong> (e.g., malignancy).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Chronic Kidney Disease (CKD)<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Elevated PTH<\/strong> and <strong>secondary Hyperparathyroidism<\/strong> are common, especially in stage 3 or worse (GFR &lt;60 mL\/min\/1.73 m^2).<\/li>\n\n\n\n<li><strong>Target ranges<\/strong> of intact PTH vary by CKD stage. For example:\n<ul class=\"wp-block-list\">\n<li>Stage 3: 35\u201370 pg\/mL<\/li>\n\n\n\n<li>Stage 4: 70\u2013110 pg\/mL<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>Patients with repeated iPTH >800 pg\/mL who fail standard interventions may be candidates for <strong>parathyroidectomy<\/strong>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Hypocalcemia<\/strong>\n<ul class=\"wp-block-list\">\n<li>Elevated PTH in the face of low serum calcium can be seen with <strong>intestinal malabsorption, vitamin D deficiency, renal failure, or hereditary vitamin D resistance<\/strong>.<\/li>\n\n\n\n<li>If PTH is <strong>not<\/strong> elevated in hypocalcemia, consider <strong>primary parathyroid failure<\/strong>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Suspected or Known Bone Disease<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Elevated PTH<\/strong> is associated with <strong>hyperparathyroid bone disease<\/strong>.<\/li>\n\n\n\n<li>CKD patients often require <strong>2\u20133 times<\/strong> normal PTH for normal <a href=\"https:\/\/myendoconsult.com\/learn\/bone-turnover-markers-in-osteoporosis\/\"  data-wpil-monitor-id=\"28\">bone turnover<\/a>.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Chronic Kidney Disease and PTH Monitoring<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>In CKD, the test helps distinguish <strong>secondary Hyperparathyroidism<\/strong>, especially in:\n<ul class=\"wp-block-list\">\n<li>Stage 3: GFR 30\u201359 mL\/min\/1.73 m^2 \u2192 measure PTH every 12 months<\/li>\n\n\n\n<li>Stage 4: GFR 15\u201329 mL\/min\/1.73 m^2 \u2192 measure PTH every 3 months<\/li>\n\n\n\n<li>Stage 5: GFR &lt;15 or on dialysis \u2192 measure PTH every 3 months<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Dietary phosphorus<\/strong> restriction (800\u20131,000 mg\/day) is recommended if iPTH levels exceed target.<\/li>\n\n\n\n<li><strong>Elevated iPTH<\/strong> (>500\u2013600 pg\/mL) can indicate moderate\/severe secondary Hyperparathyroidism.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Clinical Application<\/strong> Of pTH monitoring<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>PTH is secreted in <strong>response to hypocalcemia<\/strong>, returning serum calcium to normal. When serum calcium normalizes, PTH secretion <strong>diminishes<\/strong>.<\/li>\n\n\n\n<li>This test is <strong>critical<\/strong> for diagnosing <strong>Hyperparathyroidism<\/strong> and differentiating <strong>parathyroid vs. nonparathyroid<\/strong> causes of <strong>hypercalcemia<\/strong>.<\/li>\n\n\n\n<li><strong>Simultaneous measurement<\/strong> of <strong>serum calcium<\/strong> is essential for interpretation. Many labs provide <strong>PTH\/calcium nomograms<\/strong>.<\/li>\n<\/ul>\n\n\n\n<table id=\"tablepress-138\" class=\"tablepress tablepress-id-138\">\n<thead>\n<tr class=\"row-1\">\n\t<th class=\"column-1\"><strong>Condition<\/strong><\/th><th class=\"column-2\"><strong>PTH Levels<\/strong><\/th><th class=\"column-3\"><strong>Calcium Levels<\/strong><\/th><th class=\"column-4\"><strong>Underlying Mechanism<\/strong><\/th>\n<\/tr>\n<\/thead>\n<tbody class=\"row-striping row-hover\">\n<tr class=\"row-2\">\n\t<td class=\"column-1\">Primary Hyperparathyroidism<\/td><td class=\"column-2\">Elevated<\/td><td class=\"column-3\">Elevated<\/td><td class=\"column-4\">Adenoma or carcinoma autonomously producing PTH<\/td>\n<\/tr>\n<tr class=\"row-3\">\n\t<td class=\"column-1\">Secondary Hyperparathyroidism<\/td><td class=\"column-2\">Elevated<\/td><td class=\"column-3\">Normal\/Low<\/td><td class=\"column-4\">CRF or malabsorption causing compensatory PTH increase<\/td>\n<\/tr>\n<tr class=\"row-4\">\n\t<td class=\"column-1\">Tertiary Hyperparathyroidism<\/td><td class=\"column-2\">Elevated<\/td><td class=\"column-3\">Elevated<\/td><td class=\"column-4\">Autonomous PTH production in prolonged secondary hyperparathyroidism<\/td>\n<\/tr>\n<tr class=\"row-5\">\n\t<td class=\"column-1\">Hypoparathyroidism<\/td><td class=\"column-2\">Decreased<\/td><td class=\"column-3\">Low<\/td><td class=\"column-4\">Surgical\/autoimmune ablation or compensatory response to hypercalcemia<\/td>\n<\/tr>\n<tr class=\"row-6\">\n\t<td class=\"column-1\">Pseudohyperparathyroidism<\/td><td class=\"column-2\">Elevated<\/td><td class=\"column-3\">Low<\/td><td class=\"column-4\">Congenital renal resistance to PTH<\/td>\n<\/tr>\n<tr class=\"row-7\">\n\t<td class=\"column-1\">Malignancy-related Hypercalcemia<\/td><td class=\"column-2\">Decreased\/Normal<\/td><td class=\"column-3\">Elevated<\/td><td class=\"column-4\">Ectopic PTH-related protein or bone metastasis<\/td>\n<\/tr>\n<tr class=\"row-8\">\n\t<td class=\"column-1\">Vitamin D Deficiency<\/td><td class=\"column-2\">Elevated<\/td><td class=\"column-3\">Low<\/td><td class=\"column-4\">Impaired intestinal calcium absorption<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<!-- #tablepress-138 from cache -->\n\n\n\n<p class=\"wp-block-paragraph\">In patients with <strong>secondary<\/strong> or <strong>tertiary hyperparathyroidism (HPT)<\/strong>, especially those with <strong>chronic renal failure (CRF)<\/strong> or post\u2013renal transplant, <strong>intraoperative parathyroid hormone (IOPTH) monitoring<\/strong> offers a valuable tool for guiding surgical management. By measuring the <strong>drop in PTH levels<\/strong> immediately after resecting hyperfunctioning parathyroid tissue, clinicians can confirm <strong>adequate gland removal<\/strong> and reduce the likelihood of missed or supernumerary glands.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Clinical Pearls<\/strong>:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Indicator of Surgical Success<\/strong>\n<ul class=\"wp-block-list\">\n<li>A <strong>significant decline<\/strong> in IOPTH (for example, <strong>>50\u201380%<\/strong> at 10 to 20 minutes) strongly predicts <strong>operative cure<\/strong> in both secondary (CRF-related) and tertiary (post-transplant) HPT.<\/li>\n\n\n\n<li>In some studies, a <strong>\u226590% drop<\/strong> has been associated with nearly <strong>100% specificity<\/strong>, indicating near-certain success if that threshold is met.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Practical Advantages<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Prevents Reoperation<\/strong>: Rapid IOPTH feedback helps detect any remaining hyperfunctioning parathyroid tissue, reducing the risk of persistent or recurrent disease.<\/li>\n\n\n\n<li><strong>Flexible Cutoffs<\/strong>: Different thresholds (e.g., <strong>70%\u201380%<\/strong> at 20 minutes versus <strong>>90%<\/strong> at 40 minutes) can be tailored to the clinical setting, surgical timing, and renal clearance considerations.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Role in Renal HPT<\/strong>\n<ul class=\"wp-block-list\">\n<li>Patients with <strong>CKD<\/strong> often accumulate inactive PTH fragments, affecting standard assays. Despite this, IOPTH still improves the overall cure rate when thresholds are adjusted for delayed PTH clearance.<\/li>\n\n\n\n<li><strong>Total parathyroidectomy with autotransplantation<\/strong>, guided by IOPTH, remains a mainstay for refractory secondary\/tertiary HPT.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">Overall, <strong>IOPTH monitoring<\/strong> allows surgeons to <strong>confirm complete parathyroid resection intraoperatively<\/strong>, thus minimizing failure rates and improving outcomes for renal HPT patients whose disease is resistant to medical therapy.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Test Procedure &amp; Specimen Requirements<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">For the <strong>12 hours preceding specimen collection<\/strong>, the patient should <strong>avoid taking<\/strong> any <strong>multivitamins or dietary supplements<\/strong> (including <strong>hair, skin, and nail supplements<\/strong>) that contain <strong>biotin (vitamin B7)<\/strong>. The patient should also <strong>remain fasting<\/strong> for <strong>12 hours<\/strong> before providing the specimen.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The recommended <strong>supply<\/strong> is the <strong>Sarstedt Aliquot Tube (5 mL; T914)<\/strong>. The <strong>preferred collection container<\/strong> is a <strong>serum gel tube<\/strong>, although a <strong>red-top tube<\/strong> is also acceptable. For submission, a <strong>plastic vial<\/strong> is required with a <strong>specimen volume<\/strong> of <strong>1 mL<\/strong>. After collection, <strong>centrifuge<\/strong> the sample and <strong>transfer<\/strong> the serum to the plastic vial for final submission.<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Sample Tube<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Red top<\/strong> or <strong>serum separator tube<\/strong> for serum PTH.<\/li>\n\n\n\n<li><strong>Plasma<\/strong> samples often drawn in <strong>EDTA tubes<\/strong> (check lab protocol).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Drawing the Sample<\/strong>\n<ul class=\"wp-block-list\">\n<li>Typically, an <strong>8 AM fasting<\/strong> sample is drawn.<\/li>\n\n\n\n<li><strong>PTH<\/strong> has a <strong>diurnal variation<\/strong>: highest ~2 AM, lowest ~2 PM. Adjust if the patient works nights.<\/li>\n\n\n\n<li>Obtain a <strong>serum calcium<\/strong> level simultaneously, if ordered.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Patient Instructions<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Explain<\/strong> the procedure.<\/li>\n\n\n\n<li>Generally, the patient is <strong>NPO<\/strong> (nothing by mouth except water) after midnight.<\/li>\n\n\n\n<li>Apply <strong>pressure\/pressure dressing<\/strong> to the site post-venipuncture.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Additional Insights from Research<\/strong><\/h2>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Regulation of PTH Secretion<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>CaSR<\/strong> (calcium-sensing receptor) is pivotal in <strong>familial hypocalciuric hypercalcemia<\/strong> and other genetic variants.<\/li>\n\n\n\n<li><strong>Calcimimetics<\/strong> (e.g., cinacalcet, etelcalcetide) are helpful in <strong>CKD<\/strong>-related Hyperparathyroidism or <strong>parathyroid carcinoma<\/strong>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Metabolism and Clearance<\/strong>\n<ul class=\"wp-block-list\">\n<li>The <strong>liver<\/strong> and <strong>kidney<\/strong> degrade PTH, producing multiple fragments with varying half-lives.<\/li>\n\n\n\n<li>In <strong>renal failure<\/strong>, <strong>C-terminal fragments<\/strong> accumulate, which can affect certain PTH assays.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Biologic Activity<\/strong>\n<ul class=\"wp-block-list\">\n<li>The <strong>N-terminal region<\/strong> (especially residues 1\u201334) has the main <strong>biologic effect<\/strong>.<\/li>\n\n\n\n<li>The <strong>C-terminal<\/strong> portion may have a minor or antagonistic action.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Bone Effects<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>High PTH<\/strong> => osteoclastic bone resorption (hyperparathyroid bone disease).<\/li>\n\n\n\n<li><strong>Intermittent, low-dose<\/strong> => osteoblastic bone formation (therapeutic usage in <strong>osteoporosis<\/strong>).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Clinical Relevance<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Hyperparathyroidism<\/strong>: elevated PTH with hypercalcemia.<\/li>\n\n\n\n<li><strong>Hypoparathyroidism<\/strong>: low or inappropriately normal PTH with hypocalcemia.<\/li>\n\n\n\n<li><strong>Secondary Hyperparathyroidism<\/strong> in CKD: often very <strong>high PTH<\/strong> with <strong>hypercortical<\/strong> bone changes and electrolyte derangements.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Reference<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Einbinder Y, Benchetrit S, Golan E, Zitman-Gal T. Comparison of Intact PTH and Bio-Intact PTH Assays Among Non-Dialysis Dependent Chronic Kidney Disease Patients. Ann Lab Med. 2017 Sep;37(5):381-387. doi: 10.3343\/alm.2017.37.5.381. PMID: 28643486; PMCID: PMC5500736.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Parathyroid Hormone (PTH) Blood Test Parathyroid hormone (PTH) is an 84\u2013amino-acid peptide secreted predominantly by two pairs of parathyroid glands, located behind or adjacent&hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[47],"tags":[],"class_list":["post-4422021","post","type-post","status-publish","format-standard","hentry","category-endocrine-disease-parathyroid-calcium-and-bone-metabolism"],"_links":{"self":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/posts\/4422021","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/comments?post=4422021"}],"version-history":[{"count":13,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/posts\/4422021\/revisions"}],"predecessor-version":[{"id":4422039,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/posts\/4422021\/revisions\/4422039"}],"wp:attachment":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/media?parent=4422021"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/categories?post=4422021"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/tags?post=4422021"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}