{"id":4422519,"date":"2025-01-11T22:33:26","date_gmt":"2025-01-12T04:33:26","guid":{"rendered":"https:\/\/myendoconsult.com\/learn\/topics\/hypercalcemia\/"},"modified":"2025-01-11T22:38:52","modified_gmt":"2025-01-12T04:38:52","slug":"hypercalcemia","status":"publish","type":"oen_topic","link":"https:\/\/myendoconsult.com\/learn\/topics\/hypercalcemia\/","title":{"rendered":"Hypercalcemia"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">INTRODUCTION<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Most common causes of hypercalcemia<\/strong>:\n<ol class=\"wp-block-list\">\n<li><strong><a href=\"https:\/\/myendoconsult.com\/learn\/topics\/primary-hyperparathyroidism\/\"  data-wpil-monitor-id=\"258\">Primary hyperparathyroidism<\/a> (HPT)<\/strong><\/li>\n\n\n\n<li><strong>Malignancy<\/strong><\/li>\n<\/ol>\n<\/li>\n\n\n\n<li><strong>Initial Steps<\/strong>\n<ul class=\"wp-block-list\">\n<li>Recheck <strong>serum calcium<\/strong> to confirm it is persistently elevated.<\/li>\n\n\n\n<li><strong>Review past lab values<\/strong>:\n<ul class=\"wp-block-list\">\n<li>Long-standing mild hypercalcemia (&lt;11 mg\/dL) \u2192 typical of <strong>primary HPT<\/strong><\/li>\n\n\n\n<li>Sudden onset of severe hypercalcemia (>13 mg\/dL) \u2192 typical of <strong>malignancy<\/strong><\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>Evaluate <strong>diet<\/strong> and <strong>medications<\/strong> to exclude:\n<ul class=\"wp-block-list\">\n<li><strong>Milk\u2013alkali syndrome<\/strong><\/li>\n\n\n\n<li><strong>Medication-induced<\/strong> hypercalcemia (e.g., thiazides, lithium)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">DIFFERENTIATING PTH-MEDIATED VS. NON\u2013PTH-MEDIATED HYPERCALCEMIA<\/h2>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Measure Serum PTH<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Elevated or inappropriately normal PTH<\/strong> \u2192 indicates <strong>PTH-mediated<\/strong> hypercalcemia (primary HPT).<\/li>\n\n\n\n<li><strong>Low PTH<\/strong> \u2192 suggests <strong>non\u2013PTH-mediated<\/strong> hypercalcemia (e.g., malignancy, granulomatous disease, excess vitamin D).<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">PARATHYROID HORMONE\u2013MEDIATED HYPERCALCEMIA<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Primary Hyperparathyroidism (HPT)<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Serum PTH<\/strong>: Above normal range in most, or inappropriately high-normal if hypercalcemia is present.<\/li>\n\n\n\n<li><strong>Other Lab Findings<\/strong>:\n<ol class=\"wp-block-list\">\n<li><strong>Serum inorganic phosphate (Pi)<\/strong>: Typically low (due to PTH effect on renal tubules).<\/li>\n\n\n\n<li><strong>24-hour urinary <a href=\"https:\/\/myendoconsult.com\/learn\/fractional-excretion-of-calcium-calculator\/\"  data-wpil-monitor-id=\"259\">excretion of calcium<\/a><\/strong>: Usually normal-high or above reference range in most HPT patients.\n<ul class=\"wp-block-list\">\n<li>But <strong>low urinary calcium (&lt;100 mg\/24 hr)<\/strong> suggests other causes (milk\u2013alkali syndrome, familial hypocalciuric hypercalcemia [FHH], thiazide use).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Serum 1,25-dihydroxyvitamin D [1,25(OH)\u2082D]<\/strong>: Usually increased (PTH enhances renal 1\u03b1-hydroxylation of 25[OH]D).<\/li>\n<\/ol>\n<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">NON\u2013PARATHYROID HORMONE\u2013MEDIATED HYPERCALCEMIA<\/h2>\n\n\n\n<p>When <strong>PTH is low<\/strong> in a hypercalcemic patient:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Measure PTHrP, 25(OH)D, 1,25(OH)\u2082D<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>High PTHrP<\/strong> \u2192 common in <strong>humoral hypercalcemia of malignancy<\/strong> (e.g., squamous cell carcinoma).\n<ul class=\"wp-block-list\">\n<li>Note: PTHrP does <strong>not<\/strong> stimulate 1,25(OH)\u2082D production.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>25(OH)D<\/strong> markedly increased \u2192 <strong>vitamin D intoxication<\/strong>.<\/li>\n\n\n\n<li><strong>1,25(OH)\u2082D<\/strong> elevated \u2192 suggests extrarenal 1\u03b1-hydroxylation (e.g., <strong>granulomatous disorders<\/strong>, <strong>lymphoma<\/strong>).\n<ul class=\"wp-block-list\">\n<li>Common cause: <strong>sarcoidosis<\/strong> (check chest X-ray\/CT for bilateral hilar adenopathy).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>If PTHrP, vitamin D levels are low<\/strong>\n<ul class=\"wp-block-list\">\n<li>Look for other causes of bone resorption:\n<ul class=\"wp-block-list\">\n<li><strong>Multiple myeloma<\/strong> (serum protein electrophoresis).<\/li>\n\n\n\n<li><strong>Hyperthyroidism<\/strong> (TSH).<\/li>\n\n\n\n<li><strong>Vitamin A intoxication<\/strong>.<\/li>\n\n\n\n<li><strong>Immobilization<\/strong> (especially in young patients).<\/li>\n\n\n\n<li><strong>Milk\u2013alkali syndrome<\/strong> (increased Ca\u00b2\u207a intake + decreased renal excretion).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">OTHER CAUSES OF APPARENT HYPERCALCEMIA<\/h2>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Pseudohypercalcemia<\/strong>\n<ul class=\"wp-block-list\">\n<li>Lab artifact: total calcium is high but <strong>ionized calcium is normal<\/strong>.<\/li>\n\n\n\n<li>Often from elevated proteins (e.g., multiple myeloma paraproteins).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Familial Hypocalciuric Hypercalcemia (FHH)<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Rare autosomal dominant<\/strong> inactivating mutation of the <strong>calcium-sensing receptor (CaSR)<\/strong>.<\/li>\n\n\n\n<li>Typical labs:\n<ul class=\"wp-block-list\">\n<li>Mild hypercalcemia, borderline high\/normal PTH, <strong>hypocalciuria<\/strong> (&lt;1% fractional excretion).<\/li>\n\n\n\n<li>Normal or slightly elevated serum magnesium.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Clinical<\/strong>: usually asymptomatic, benign course.<\/li>\n\n\n\n<li><strong>Management<\/strong>: No surgery needed. Testing family members is important to avoid unnecessary parathyroidectomy.<\/li>\n<\/ul>\n<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"<p>INTRODUCTION DIFFERENTIATING PTH-MEDIATED VS. NON\u2013PTH-MEDIATED HYPERCALCEMIA PARATHYROID HORMONE\u2013MEDIATED HYPERCALCEMIA Primary Hyperparathyroidism (HPT) NON\u2013PARATHYROID HORMONE\u2013MEDIATED HYPERCALCEMIA When PTH is low in a hypercalcemic patient: OTHER CAUSES OF APPARENT HYPERCALCEMIA<\/p>\n","protected":false},"featured_media":0,"template":"","oen_topic_chapter":[687],"class_list":["post-4422519","oen_topic","type-oen_topic","status-publish","hentry","oen_topic_chapter-parathyroid-gland","post-wrapper","thrv_wrapper"],"_links":{"self":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic\/4422519","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic"}],"about":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/types\/oen_topic"}],"version-history":[{"count":3,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic\/4422519\/revisions"}],"predecessor-version":[{"id":4422522,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic\/4422519\/revisions\/4422522"}],"wp:attachment":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/media?parent=4422519"}],"wp:term":[{"taxonomy":"oen_topic_chapter","embeddable":true,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic_chapter?post=4422519"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}