{"id":4422529,"date":"2025-01-11T22:50:48","date_gmt":"2025-01-12T04:50:48","guid":{"rendered":"https:\/\/myendoconsult.com\/learn\/topics\/hypoparathyroidism\/"},"modified":"2025-01-13T06:30:40","modified_gmt":"2025-01-13T12:30:40","slug":"hypoparathyroidism","status":"publish","type":"oen_topic","link":"https:\/\/myendoconsult.com\/learn\/topics\/hypoparathyroidism\/","title":{"rendered":"Hypoparathyroidism"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">PATHOPHYSIOLOGY OF HYPOPARATHYROIDISM<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Key Biochemical Findings<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Low serum calcium<\/strong> (usually &lt;7 mg\/dL)<\/li>\n\n\n\n<li><strong>High serum inorganic phosphorus (Pi)<\/strong> (typically >5 mg\/dL)<\/li>\n\n\n\n<li><strong>Decreased urinary excretion<\/strong> of both calcium and phosphate<\/li>\n\n\n\n<li><strong>Absence of PTH actions<\/strong> explains these laboratory results.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Underlying Mechanisms<\/strong>\n<ol class=\"wp-block-list\">\n<li><strong>Decreased Bone Resorption<\/strong>: <a href=\"https:\/\/myendoconsult.com\/learn\/normal-pth-levels-by-age\/\"  data-wpil-monitor-id=\"350\">PTH normally<\/a> stimulates osteoclasts. Without PTH, there is minimal release of calcium into the bloodstream.<\/li>\n\n\n\n<li><strong>Diminished Calcium Absorption<\/strong>: PTH deficiency \u2192 decreased renal 1\u03b1-hydroxylation of 25-hydroxyvitamin D (25[OH]D) to 1,25-dihydroxyvitamin D (1,25[OH]\u2082D) \u2192 reduced GI calcium absorption.<\/li>\n\n\n\n<li><strong>Excess Phosphate Retention<\/strong>: Without PTH, the renal tubules reabsorb phosphate excessively, elevating serum phosphate. High Pi itself also depresses serum calcium.<\/li>\n<\/ol>\n<\/li>\n\n\n\n<li><strong>Diagnostic Triad<\/strong><ol><li><strong>Low serum calcium<\/strong><\/li><li><strong>High serum phosphate<\/strong><\/li><li><strong>Normal serum alkaline phosphatase<\/strong> (in the absence of renal failure or malabsorption)<\/li><\/ol>This triad is essentially pathognomonic for hypoparathyroidism.<\/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\">CAUSES OF PTH DEFICIENCY<\/h2>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Postsurgical Hypoparathyroidism (Most Common)<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Neck Surgery<\/strong>: Subtotal or total thyroidectomy, parathyroid surgery, or other neck cancer surgery.<\/li>\n\n\n\n<li>Often <strong>transient<\/strong> if some viable parathyroid tissue remains or if the parathyroid glands recover from surgical trauma.<\/li>\n\n\n\n<li><strong>Permanent<\/strong> if all parathyroid tissue was removed or irreversibly damaged.<\/li>\n\n\n\n<li><strong>Hungry Bone Syndrome<\/strong>: Occurs after removal of a hyperfunctioning parathyroid adenoma (bone avidly takes up calcium postoperatively).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Autoimmune Hypoparathyroidism<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Autoimmune Destruction<\/strong> of parathyroid glands, often associated with <strong><a href=\"https:\/\/myendoconsult.com\/learn\/topics\/polyglandular-syndrome\/\"  data-wpil-monitor-id=\"347\">polyglandular autoimmune syndrome<\/a> type 1<\/strong> (with adrenal insufficiency + chronic mucocutaneous candidiasis).<\/li>\n\n\n\n<li>Rarely, activating autoantibodies to the Ca\u00b2\u207a-sensing receptor (CaSR) can cause hypoparathyroidism.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Developmental or Regulatory Defects<\/strong>\n<ul class=\"wp-block-list\">\n<li>Abnormal parathyroid gland <strong>embryologic development<\/strong> or <strong>PTH synthesis<\/strong>.<\/li>\n\n\n\n<li>Mutations affecting regulation of <strong>PTH production<\/strong>, <strong>secretion<\/strong>, or <strong>action<\/strong>.<\/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\">GENETIC CAUSES OF HYPOPARATHYROIDISM<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Abnormal Parathyroid Development<\/strong>\n<ul class=\"wp-block-list\">\n<li>X-linked or autosomal recessive mutations (e.g., GCM2 gene, encoding a key transcription factor).<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>PreproPTH Gene Mutations<\/strong>\n<ul class=\"wp-block-list\">\n<li>Defects in the PTH precursor protein \u2192 no biologically active PTH.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Autosomal Dominant Activating Mutations of the CaSR<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Lower calcium set point<\/strong> for PTH release \u2192 PTH not secreted until hypocalcemia is severe.<\/li>\n\n\n\n<li><strong>High urinary <a href=\"https:\/\/myendoconsult.com\/learn\/fractional-excretion-of-calcium-calculator\/\"  data-wpil-monitor-id=\"348\">calcium excretion<\/a><\/strong> (unlike other forms of hypoparathyroidism, which generally show low urinary calcium).<\/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\">PSEUDOHYPOPARATHYROIDISM (HYPOCALCEMIA DESPITE HIGH PTH)<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Definition<\/strong>: Serum PTH is <strong>high<\/strong>, but hypocalcemia persists because of <strong>end-organ (bone, kidney) resistance<\/strong> or other defects in vitamin D metabolism.<\/li>\n\n\n\n<li><strong>Key Features<\/strong>:\n<ul class=\"wp-block-list\">\n<li>Inadequate PTH-induced bone resorption<\/li>\n\n\n\n<li>Decreased renal 1,25(OH)\u2082D production<\/li>\n\n\n\n<li>Hypocalcemia remains despite elevated PTH.<\/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\">CLINICAL MANIFESTATIONS OF ACUTE HYPOCALCEMIA<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Range of Symptoms<\/strong>\n<ul class=\"wp-block-list\">\n<li>Minor: Anxiety, mild muscle spasms or cramps, perioral and acral paresthesias<\/li>\n\n\n\n<li>Severe: Tetany, seizures, laryngospasm, papilledema, heart failure<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Acute Tetany<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Neuromuscular Irritability<\/strong>: Early signs include perioral numbness, tingling (hands\/feet), muscle cramps, hyperreflexia, photophobia, diplopia.<\/li>\n\n\n\n<li>Advanced symptoms:\n<ul class=\"wp-block-list\">\n<li><strong>Carpopedal Spasm<\/strong> (adduction of thumb, finger extension, wrist flexion)<\/li>\n\n\n\n<li><strong>Laryngospasm<\/strong> (stridor due to glottic spasm)<\/li>\n\n\n\n<li><strong>Seizures<\/strong> (grand mal, petit mal, focal)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Clinical Tests<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Trousseau Sign<\/strong>: Carpopedal spasm induced by inflating a blood pressure cuff above systolic BP for ~3 minutes.<\/li>\n\n\n\n<li><strong><a href=\"https:\/\/myendoconsult.com\/learn\/positive-chvostek-sign\/\"  data-wpil-monitor-id=\"349\">Chvostek Sign<\/a><\/strong>: Ipsilateral facial muscle contraction when tapping the facial nerve below the zygoma. (Not fully specific for hypocalcemia; can also be positive in alkalosis.)<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Other Findings<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Chronic Hypocalcemia<\/strong>: Cataracts, basal ganglia calcification, extrapyramidal issues, abnormal dentition (enamel\/dental hypoplasia).<\/li>\n\n\n\n<li><strong>Skin\/Hair Changes<\/strong>: Brittle nails with transverse grooves, dry\/coarse skin, sparse\/coarse scalp hair.<\/li>\n\n\n\n<li><strong>Cardiac Effects<\/strong>: Prolonged Q-T interval on ECG, possible arrhythmias (e.g., torsades de pointes), heart failure in severe cases.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Common Causes<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Postsurgical<\/strong> hypoparathyroidism remains the leading cause of severe acute hypocalcemia.<\/li>\n\n\n\n<li><strong>Diagnosis<\/strong>: Recognized as an endocrine emergency \u2192 prompt IV calcium therapy to prevent life-threatening complications (seizures, laryngospasm, etc.).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>PATHOPHYSIOLOGY OF HYPOPARATHYROIDISM CAUSES OF PTH DEFICIENCY GENETIC CAUSES OF HYPOPARATHYROIDISM PSEUDOHYPOPARATHYROIDISM (HYPOCALCEMIA DESPITE HIGH PTH) CLINICAL MANIFESTATIONS OF ACUTE HYPOCALCEMIA<\/p>\n","protected":false},"featured_media":0,"template":"","oen_topic_chapter":[687],"class_list":["post-4422529","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\/4422529","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\/4422529\/revisions"}],"predecessor-version":[{"id":4422867,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic\/4422529\/revisions\/4422867"}],"wp:attachment":[{"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/media?parent=4422529"}],"wp:term":[{"taxonomy":"oen_topic_chapter","embeddable":true,"href":"https:\/\/myendoconsult.com\/learn\/wp-json\/wp\/v2\/oen_topic_chapter?post=4422529"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}