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Chapter 32 Disorders of Endocrine Control of Growth and Metabolism Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins HypothalamusPituitary Axis • Releasing hormones from hypothalamus tell the pituitary what to release into the blood • Trophic hormones from the pituitary tell specific peripheral glands to grow and produce their hormones Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Hormone Disorders Tertiary: abnormality in stimulation from the hypothalamus Secondary: abnormality in stimulation from the pituitary Primary: abnormality in the gland Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Pituitary Hormones Growth hormone FSH and LH TSH stimulate gonads stimulates thyroid ACTH stimulates adrenal cortex Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Question Which hormone(s) is/are secreted by the ovaries and testes? a. GH b. FSH & LH c. TSH d. ACTH & GH Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer b. FSH & LH Gonads are sex organs (ovaries and testes). These organs secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins The Hypothalamus Controls Growth Hormone Release Hypothalamus • GH secretion stimulated by: – Hypoglycemia, fasting, starvation GHRH stimulates – Stress Somatostatin inhibits • GH inhibited by: – Increased glucose levels, free fatty acid release, and obesity – Cortisol Anterior pituitary Growth hormone Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Functions of Growth Hormone Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Growth Hormone Deficiency • Idiopathic GH deficiency – Lacks hypothalamic GHRH • Pituitary tumors, agenesis of the pituitary – Cannot produce GH • Laron-type dwarfism – Hereditary defect in IGF production Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Growth Hormone Excess • In childhood: gigantism • In adulthood: acromegaly Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Question Tell whether the following statement is true or false: GH deficiency may result in dwarfism. Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer True Laron-type dwarfism is caused by a genetic inability to produce normal amounts of GH. Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins The Hypothalamus Controls Gonadal Hormone Release Hypothalamus • Excessive GnRH secretion can be stimulated by: – Hypothalamus tumors – Pituitary tumors • Giving high levels of GnRH causes the pituitary to become less responsive and reduces the effects of abnormal GnRH secretion GnRH stimulates anterior pituitary FSH LH production of gametes and gonadal hormones Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Thyroid Control • Thyroid releases T3 and T4 • Both are carried by binding proteins • T3 stimulates metabolism • T4 is inactive until converted into T3 in the tissues • Both exert negative feedback on the hypothalamus Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Thyroid Insufficiency Due to Lack of I• T3 and T4 are not made • There is no negative feedback to the hypothalamus • TRH and TSH continue to be made • If it is able, the thyroid will grow in response to the TSH Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Thyroid Imbalances • Hypothyroidism – Congenital – Acquired º Hashimoto thyroiditis º Thyroidectomy • Hyperthyroidism (thyrotoxicosis) – Graves disease – Thyroid tumors Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Question Tell whether the following statement is true or false: Simple goiter is caused by increased production of thyroid hormone. Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Answer False Simple goiter is the result of iodine (I) insufficiency. Since I is necessary in order to produce thyroid hormone, a deficiency results in low serum levels of T3/T4. This causes TSH to stimulate the thyroid gland to make more hormone (which it cannot do because it needs I). The cells of the thyroid gland hypertrophy in an effort to function (make thyroid hormone). Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Major Adrenal Cortical Hormones Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Actions of Cortisol cortisol catabolism increased plasma proteins increased muscle breakdown free fatty acids increased immune/ inflammatory systems suppressed SNS response increased blood glucose increased Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Adrenal Cortical Disorders • Adrenal cortical insufficiency: inability to make all 3 hormones – Primary adrenal cortical insufficiency (Addison disease) – Secondary adrenal cortical insufficiency – Acute adrenal crisis • Excessive adrenal secretion – Glucocorticoid hormone excess (Cushing syndrome) – Hyperaldosteronism • Congenital adrenal hyperplasia – Decreased cortisol synthesis; other hormones may be increased or decreased Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Clinical Manifestations of Addison Disease Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Clinical Manifestations of Cushing Syndrome Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Scenario Three men have adrenal problems… • One has hypoaldosteronism, one has an inability to make cortisol, and one has an inability to make testosterone. Question • Which of them is most likely to develop: • Hypotension? • High CRH levels? • Hypoglycemia? • Hypervirilization? • Decreased libido? • Hyperkalemia? Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins Scenario Two women have benign pituitary tumors… • One woman has lost weight and complains of being hot all the time; she presents as thin and nervous, with tachycardia and exophthalmos • The second woman has gained weight in her abdomen and presents with a round face and thin arms and legs with stretch marks; she says that at her last checkup her doctor told her she was prediabetic Question • What hormones are being secreted by the pituitary tumors in these patients? Why? Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins