1 Endocrine Pathophysiology I Kyong Soo Park Dept of MMBS & Dept of Internal Medicine, Seoul National University College of Medicine

Introduction The endocrine system assists the nervous system with communication and control of the body Endocrine glands They are ductless They secrete hormones into bloodstream There are also similar glands called paracrine and autocrine glands that are quasi-endocrine Exocrine glands They have ducts They deliver their products directly to a specific site

Hormone: is a chemical messenger secreted by one endocrine gland or cell into the bloodstream and targeted toward cells in another organ

General Characteristics of the Endocrine System The endocrine and nervous systems communicate using chemical signals

Endocrine Gland

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8 Chemistry of Hormones Chemically, hormones are either: Steroid or steroid-like hormones such as: Sex hormones Adrenal cortex hormones Non-steroid hormones such as: Amines Proteins Peptides Glycoproteins

Action of Steroid Hormones

Action of Non-Steroid Hormones

Control of Hormonal Secretions Hormones can be short-lived or may last for days Amines (2-3 minutes) polypeptides (4-40 minutes) steroid and proteins (4-170 minutes), thyroid hormones ( days) Primarily controlled by negative feedback mechanism Hormone secretions are precisely regulated Nervous system (a) (b) (c) Target cells Action Target cells Action – ––– Anterior pituitary gland Action Hypothalamus Peripheral endocrine gland Target cells Endocrine gland Changing level of substance in plasma Endocrine gland

Optic nerve Sphenoid bone Hypothalamus Optic chiasma Sella turcica Third ventricle Trochlear nerve Basilar artery Anterior cerebral artery Pituitary stalk (Infundibulum) Anterior lobe of pituitary gland Sphenoidal sinus Posterior lobe of pituitary gland Oculomotor nerve Pituitary Gland Lies at the base of the brain in the sella turcica Consists of two distinct portions: Anterior pituitary (adenohypophysis) Posterior pituitary (neurohypophysis)

Anterior Pituitary Hormones Hypothalamic releasing hormones stimulate cells of anterior pituitary to release hormones Hypophyseal veins Optic chiasma Capillary bed Third ventricle Anterior lobe of pituitary gland Capillary bed Hypophyseal portal veins Secretory cells of anterior pituitary gland Neurosecretory cells that secrete releasing hormones Superior hypophyseal artery Anterior pituitary Peripheral endocrine gland Hypothalamus Target cells (Hormone 3) + –– – + + Inhibition Stimulation Releasing hormone (Hormone 1) Anterior pituitary hormone (Hormone 2) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

ThyroidMammary glandOvaryTestisBoneMuscle Hormones fromAnterior Pituitary Hormones from Hypothalamus GHRH Growth hormone- releasing hormone SS Somatostatin PRF Prolactin- releasing factor PIH Prolactin- release inhibiting hormone TRH Thyrotropin- releasing hormone CRH Corticotropin- releasing hormone GnRH Gonadotropin- releasing hormone GH Growth hormone PRL Prolactin TSH Thyroid- stimulating hormone ACTH Adrenocorticotropic hormone LH Luteinizing hormone FSH Follicle- stimulating hormone Adipose tissue Adrenal cortex

Posterior Pituitary Hormones Structurally consists of nerve fibers and neuroglia v. glandular epithelial cells of the anterior pituitary gland The nerve fibers originate in the hypothalamus Two hormones are produced: Antidiuretic hormone (vasopressin) Oxytocin Hypophyseal veins Optic chiasma Capillary bed Posterior lobe of pituitary gland Third ventricle Hypothalamus Neurosecretory cells that secrete releasing hormones Superior hypophyseal artery Neurosecretory cells that secrete posterior pituitary hormones Inferior hypophyseal artery Sella turcica of sphenoid bone

Thyroid Gland Follicular cells Colloid Extrafollicular cells Larynx Colloid Isthmus (a) (b) Thyroid gland Follicular cell Extrafollicular cell The thyroid gland has two lateral lobes and lies just below the larynx It produces three hormones: T4 (thyroxine), T3 (triiodothyronine), Calcitonin

Thyroid Hormones OH O II CH 2 II OH O I CH 2 II NH 2 CHCOOH Thyroxine (T 4 )Triiodothyronine (T 3 )

Parathyroid Glands The parathyroid glands are on the posterior surface of the thyroid gland There are typically four parathyroid glands It secretes one hormone: PTH (parathyroid hormone or parathormone) Posterior view Esophagus Pharynx Thyroid gland Parathyroid glands Trachea Secretory cells Capillaries

Target cells Action – Changing level of substance in plasma Endocrine gland

Adrenal Glands The adrenal glands are closely associated with the kidneys The gland sits like a cap on each kidney Hormones are secreted from two different areas of the gland, the adrenal cortex and the adrenal medulla Numerous hormones are secreted by the adrenal glands Adrenal gland Kidney Adrenal cortex (a) Zona glomerulosa Connective tissue capsule (b) Zona fasciculata Zona reticularis Adrenal medulla Adrenal cortex Adrenal medulla Surface of adrenal gland

Hormones of the Adrenal Gland

Cushing’s syndromeAddison’s disease

Pancreas The pancreas has two major types of secretory tissue This is why it is a dual functioning organ as both an exocrine gland and endocrine gland Pancreatic islet (Islet of Langerhans) GallbladderCommon bile duct Pancreatic duct PancreasDuct Capillary Small intestine Digestive enzyme- secreting cells Pancreatic islet (Islet of Langerhans) Hormone-secreting islet cells

Hormones of the Pancreatic Islets

Other Endocrine Glands Pineal Gland Secretes melatonin Regulates circadian rhythms Thymus Gland Secretes thymosins – Promotes development of certain lymphocytes Important in role of immunity after puberty, it starts to shrink and become replaced by fat Reproductive Organs Ovaries produce estrogens and progesterone Testes produce testosterone Placenta produces estrogens, progesterone, and gonadotropin Other organs: digestive glands, heart, and kidney