{"id":5077,"date":"2025-11-26T19:19:57","date_gmt":"2025-11-27T00:19:57","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/?post_type=chapter&#038;p=5077"},"modified":"2025-12-07T21:50:02","modified_gmt":"2025-12-08T02:50:02","slug":"endocrine-system-thyroid-parathyroid-and-adrenal-gland","status":"web-only","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/chapter\/endocrine-system-thyroid-parathyroid-and-adrenal-gland\/","title":{"raw":"9p3 Endocrine System \u2013 Thyroid, Parathyroid, and Adrenal Gland","rendered":"9p3 Endocrine System \u2013 Thyroid, Parathyroid, and Adrenal Gland"},"content":{"raw":"<h1><strong>The Thyroid Gland<\/strong><\/h1>\r\n<ul>\r\n \t<li>Located in the neck region.<\/li>\r\n \t<li>Produces two main thyroid hormones: <strong>T<sub>4<\/sub> (Thyroxine)<\/strong>\u00a0and\u00a0<strong>T<sub>3<\/sub> (Triiodothyronine)<\/strong>.<\/li>\r\n<\/ul>\r\n<strong>a) Function of Thyroid Hormones:<\/strong>\r\n<ul>\r\n \t<li style=\"list-style-type: none\">\r\n<ul>\r\n \t<li>Regulate\u00a0<strong>metabolic rate<\/strong>.<\/li>\r\n \t<li>Control the\u00a0<strong>basal metabolic rate<\/strong>, which is the rate of reactions throughout the body.<\/li>\r\n \t<li>Play a key role in\u00a0<strong>thermoregulation<\/strong>\u00a0(body heat regulation).<\/li>\r\n \t<li>Influence\u00a0<strong>cellular function<\/strong>\u00a0by dictating enzymatic reaction rates.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<strong>Importance in Development<\/strong>\r\n<ul>\r\n \t<li>Essential during childhood for\u00a0<strong>growth<\/strong>\u00a0and\u00a0<strong>nervous system development<\/strong>.<\/li>\r\n \t<li>Regulating cellular reactions helps prevent large issues in growth and function.<\/li>\r\n<\/ul>\r\n<strong>b) Calcitonin<\/strong>\r\n<ul>\r\n \t<li>Secreted by the thyroid gland.<\/li>\r\n \t<li><strong>Function:<\/strong>\r\n<ul>\r\n \t<li>Regulates\u00a0<strong>calcium ion levels<\/strong>\u00a0in the blood.<\/li>\r\n \t<li>When blood calcium is\u00a0<strong>high<\/strong>: Calcitonin is released to\u00a0<strong>lower<\/strong> calcium levels by inhibiting osteoclast activity.<\/li>\r\n \t<li>Critical for\u00a0<strong>bone health<\/strong>,\u00a0<strong>heart function<\/strong>,\u00a0<strong>nervous system<\/strong>, and\u00a0<strong>skeletal muscle<\/strong>\u00a0activity.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<strong>c) Parathyroid Glands<\/strong>\r\n<ul>\r\n \t<li>Four small glands located on top of the thyroid gland.<\/li>\r\n \t<li>Secrete\u00a0<strong>parathyroid hormone (PTH)<\/strong>.<\/li>\r\n \t<li><strong>Function:<\/strong>\r\n<ul>\r\n \t<li>Opposes calcitonin.<\/li>\r\n \t<li>When blood calcium is\u00a0<strong>low<\/strong>:\r\n<ol>\r\n \t<li>PTH is released to\u00a0<strong>increase<\/strong> calcium levels by stimulating osteoblasts to release RANKL which increases osteoclast activity.<\/li>\r\n \t<li>PTH stimulates an increase in <strong>calcitriol<\/strong> release by the kidneys.\r\n<ul>\r\n \t<li><strong>Calcitriol<\/strong> is a hormone that increase the <strong>absorption<\/strong> of <strong>dietary calcium<\/strong> by intestinal cells.<\/li>\r\n<\/ul>\r\n<\/li>\r\n \t<li>PTH stimulates <strong>kidneys<\/strong> to <strong>reabsorb<\/strong> more calcium, resulting in less calcium being excreted in urine.<\/li>\r\n<\/ol>\r\n<\/li>\r\n \t<li>Vital for\u00a0<strong>bone<\/strong>,\u00a0<strong>nerve<\/strong>, and\u00a0<strong>muscle<\/strong>\u00a0function.<\/li>\r\n \t<li>Maintains\u00a0<strong>serum calcium homeostasis<\/strong>.<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<h1><strong>The Adrenal Glands<\/strong><\/h1>\r\n<ul>\r\n \t<li>Located on top of the kidneys.<\/li>\r\n \t<li>Consist of two main parts:<\/li>\r\n<\/ul>\r\n<h1><strong>a) The Adrenal Medulla (Inner part)<\/strong><\/h1>\r\n<ul>\r\n \t<li>Secretes\u00a0<strong>epinephrine (adrenaline)<\/strong>\u00a0and\u00a0<strong>norepinephrine<\/strong>.<\/li>\r\n \t<li>These act as both\u00a0<strong>neurotransmitters<\/strong>\u00a0and\u00a0<strong>hormones<\/strong>.<\/li>\r\n \t<li><strong>Function during \"Fight or Flight\":<\/strong>\r\n<ul>\r\n \t<li>When in SNS mode, these hormones are released into the bloodstream.<\/li>\r\n \t<li>Prepare the body for rapid activity (increased heart rate, energy mobilization).<\/li>\r\n<\/ul>\r\n<\/li>\r\n<\/ul>\r\n<h1><strong>b) The Adrenal Cortex (Outer part)<\/strong><\/h1>\r\n<ul>\r\n \t<li>Produces\u00a0<strong>cortisol<\/strong>,\u00a0<strong>aldosterone<\/strong>, and\u00a0<strong>androgens<\/strong>.<\/li>\r\n<\/ul>\r\n<strong>Functions of Adrenal Cortex Hormones<\/strong>\r\n\r\n<strong>Cortisol (a glucocorticoid)<\/strong>\r\n<ul>\r\n \t<li><strong>Anti-inflammatory<\/strong>.<\/li>\r\n \t<li>Suppresses\u00a0<strong>immune response<\/strong>.<\/li>\r\n \t<li><strong>Catabolic:<\/strong>\u00a0Breaks down proteins into glucose for energy.<\/li>\r\n \t<li>Involved in\u00a0<strong>metabolic control<\/strong>\u00a0and\u00a0<strong>resistance to stress<\/strong>\u00a0(e.g., during starvation).<\/li>\r\n \t<li><strong>Categories:<\/strong>\u00a0Cortisone and cortisol.<\/li>\r\n<\/ul>\r\n<strong>Aldosterone<\/strong>\r\n<ul>\r\n \t<li>Regulates\u00a0<strong>salt-water balance<\/strong>\u00a0in blood.<\/li>\r\n \t<li>Works alongside\u00a0<strong>antidiuretic hormone<\/strong>\u00a0and\u00a0<strong>cortisol<\/strong>.<\/li>\r\n \t<li>Supports\u00a0<strong>metabolic processes<\/strong>.<\/li>\r\n<\/ul>\r\n<strong>Androgens<\/strong>\r\n<ul>\r\n \t<li>Include hormones like\u00a0<strong>testosterone<\/strong>.<\/li>\r\n \t<li>Secreted by the adrenal cortex.<\/li>\r\n \t<li>In females, provide a small amount of\u00a0<strong>testosterone<\/strong>.<\/li>\r\n \t<li>Important for\u00a0<strong>skeletal muscle maintenance<\/strong>\u00a0and\u00a0<strong>growth<\/strong>.<\/li>\r\n<\/ul>\r\n<h1><strong>The Adrenal Gland - Stress Response and Catabolism<\/strong><\/h1>\r\n<ul>\r\n \t<li>During biological stress (such as starvation),\u00a0<strong>glucocorticoids<\/strong>\u00a0promote\u00a0<strong>catabolism<\/strong>, generating glucose from proteins.<\/li>\r\n \t<li>This process helps\u00a0<strong>survive stressful conditions<\/strong>.<\/li>\r\n<\/ul>\r\n<h1><strong>The Adrenal Medulla and Fight or Flight<\/strong><\/h1>\r\n<ul>\r\n \t<li>During SNS activation, the medulla secretes\u00a0<strong>epinephrine<\/strong>\u00a0and\u00a0<strong>norepinephrine<\/strong>.<\/li>\r\n \t<li>These hormones prepare the body for rapid response during\u00a0<strong>fight or flight<\/strong>\u00a0situations.<\/li>\r\n<\/ul>","rendered":"<h1><strong>The Thyroid Gland<\/strong><\/h1>\n<ul>\n<li>Located in the neck region.<\/li>\n<li>Produces two main thyroid hormones: <strong>T<sub>4<\/sub> (Thyroxine)<\/strong>\u00a0and\u00a0<strong>T<sub>3<\/sub> (Triiodothyronine)<\/strong>.<\/li>\n<\/ul>\n<p><strong>a) Function of Thyroid Hormones:<\/strong><\/p>\n<ul>\n<li style=\"list-style-type: none\">\n<ul>\n<li>Regulate\u00a0<strong>metabolic rate<\/strong>.<\/li>\n<li>Control the\u00a0<strong>basal metabolic rate<\/strong>, which is the rate of reactions throughout the body.<\/li>\n<li>Play a key role in\u00a0<strong>thermoregulation<\/strong>\u00a0(body heat regulation).<\/li>\n<li>Influence\u00a0<strong>cellular function<\/strong>\u00a0by dictating enzymatic reaction rates.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><strong>Importance in Development<\/strong><\/p>\n<ul>\n<li>Essential during childhood for\u00a0<strong>growth<\/strong>\u00a0and\u00a0<strong>nervous system development<\/strong>.<\/li>\n<li>Regulating cellular reactions helps prevent large issues in growth and function.<\/li>\n<\/ul>\n<p><strong>b) Calcitonin<\/strong><\/p>\n<ul>\n<li>Secreted by the thyroid gland.<\/li>\n<li><strong>Function:<\/strong>\n<ul>\n<li>Regulates\u00a0<strong>calcium ion levels<\/strong>\u00a0in the blood.<\/li>\n<li>When blood calcium is\u00a0<strong>high<\/strong>: Calcitonin is released to\u00a0<strong>lower<\/strong> calcium levels by inhibiting osteoclast activity.<\/li>\n<li>Critical for\u00a0<strong>bone health<\/strong>,\u00a0<strong>heart function<\/strong>,\u00a0<strong>nervous system<\/strong>, and\u00a0<strong>skeletal muscle<\/strong>\u00a0activity.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><strong>c) Parathyroid Glands<\/strong><\/p>\n<ul>\n<li>Four small glands located on top of the thyroid gland.<\/li>\n<li>Secrete\u00a0<strong>parathyroid hormone (PTH)<\/strong>.<\/li>\n<li><strong>Function:<\/strong>\n<ul>\n<li>Opposes calcitonin.<\/li>\n<li>When blood calcium is\u00a0<strong>low<\/strong>:\n<ol>\n<li>PTH is released to\u00a0<strong>increase<\/strong> calcium levels by stimulating osteoblasts to release RANKL which increases osteoclast activity.<\/li>\n<li>PTH stimulates an increase in <strong>calcitriol<\/strong> release by the kidneys.\n<ul>\n<li><strong>Calcitriol<\/strong> is a hormone that increase the <strong>absorption<\/strong> of <strong>dietary calcium<\/strong> by intestinal cells.<\/li>\n<\/ul>\n<\/li>\n<li>PTH stimulates <strong>kidneys<\/strong> to <strong>reabsorb<\/strong> more calcium, resulting in less calcium being excreted in urine.<\/li>\n<\/ol>\n<\/li>\n<li>Vital for\u00a0<strong>bone<\/strong>,\u00a0<strong>nerve<\/strong>, and\u00a0<strong>muscle<\/strong>\u00a0function.<\/li>\n<li>Maintains\u00a0<strong>serum calcium homeostasis<\/strong>.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h1><strong>The Adrenal Glands<\/strong><\/h1>\n<ul>\n<li>Located on top of the kidneys.<\/li>\n<li>Consist of two main parts:<\/li>\n<\/ul>\n<h1><strong>a) The Adrenal Medulla (Inner part)<\/strong><\/h1>\n<ul>\n<li>Secretes\u00a0<strong>epinephrine (adrenaline)<\/strong>\u00a0and\u00a0<strong>norepinephrine<\/strong>.<\/li>\n<li>These act as both\u00a0<strong>neurotransmitters<\/strong>\u00a0and\u00a0<strong>hormones<\/strong>.<\/li>\n<li><strong>Function during &#8220;Fight or Flight&#8221;:<\/strong>\n<ul>\n<li>When in SNS mode, these hormones are released into the bloodstream.<\/li>\n<li>Prepare the body for rapid activity (increased heart rate, energy mobilization).<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h1><strong>b) The Adrenal Cortex (Outer part)<\/strong><\/h1>\n<ul>\n<li>Produces\u00a0<strong>cortisol<\/strong>,\u00a0<strong>aldosterone<\/strong>, and\u00a0<strong>androgens<\/strong>.<\/li>\n<\/ul>\n<p><strong>Functions of Adrenal Cortex Hormones<\/strong><\/p>\n<p><strong>Cortisol (a glucocorticoid)<\/strong><\/p>\n<ul>\n<li><strong>Anti-inflammatory<\/strong>.<\/li>\n<li>Suppresses\u00a0<strong>immune response<\/strong>.<\/li>\n<li><strong>Catabolic:<\/strong>\u00a0Breaks down proteins into glucose for energy.<\/li>\n<li>Involved in\u00a0<strong>metabolic control<\/strong>\u00a0and\u00a0<strong>resistance to stress<\/strong>\u00a0(e.g., during starvation).<\/li>\n<li><strong>Categories:<\/strong>\u00a0Cortisone and cortisol.<\/li>\n<\/ul>\n<p><strong>Aldosterone<\/strong><\/p>\n<ul>\n<li>Regulates\u00a0<strong>salt-water balance<\/strong>\u00a0in blood.<\/li>\n<li>Works alongside\u00a0<strong>antidiuretic hormone<\/strong>\u00a0and\u00a0<strong>cortisol<\/strong>.<\/li>\n<li>Supports\u00a0<strong>metabolic processes<\/strong>.<\/li>\n<\/ul>\n<p><strong>Androgens<\/strong><\/p>\n<ul>\n<li>Include hormones like\u00a0<strong>testosterone<\/strong>.<\/li>\n<li>Secreted by the adrenal cortex.<\/li>\n<li>In females, provide a small amount of\u00a0<strong>testosterone<\/strong>.<\/li>\n<li>Important for\u00a0<strong>skeletal muscle maintenance<\/strong>\u00a0and\u00a0<strong>growth<\/strong>.<\/li>\n<\/ul>\n<h1><strong>The Adrenal Gland &#8211; Stress Response and Catabolism<\/strong><\/h1>\n<ul>\n<li>During biological stress (such as starvation),\u00a0<strong>glucocorticoids<\/strong>\u00a0promote\u00a0<strong>catabolism<\/strong>, generating glucose from proteins.<\/li>\n<li>This process helps\u00a0<strong>survive stressful conditions<\/strong>.<\/li>\n<\/ul>\n<h1><strong>The Adrenal Medulla and Fight or Flight<\/strong><\/h1>\n<ul>\n<li>During SNS activation, the medulla secretes\u00a0<strong>epinephrine<\/strong>\u00a0and\u00a0<strong>norepinephrine<\/strong>.<\/li>\n<li>These hormones prepare the body for rapid response during\u00a0<strong>fight or flight<\/strong>\u00a0situations.<\/li>\n<\/ul>\n","protected":false},"author":1370,"menu_order":9,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["zoe-soon"],"pb_section_license":"cc-by-nc-sa"},"chapter-type":[],"contributor":[60],"license":[57],"class_list":["post-5077","chapter","type-chapter","status-web-only","hentry","contributor-zoe-soon","license-cc-by-nc-sa"],"part":63,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/5077","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/users\/1370"}],"version-history":[{"count":8,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/5077\/revisions"}],"predecessor-version":[{"id":5253,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/5077\/revisions\/5253"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/parts\/63"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapters\/5077\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/media?parent=5077"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/pressbooks\/v2\/chapter-type?post=5077"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/contributor?post=5077"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathophysiology\/wp-json\/wp\/v2\/license?post=5077"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}