MT 201-BIOCHEMISTRY FOR MEDICAL LABORATORY SCIENCE LESSON: 2_FINALS THE ENDOCRINE SYSTEM FIRST SEMESTER | AY 2023-2024 membrane it will enter the nucleus. ➢ Bind to a specific protein within the nucleus ➢ Bind to specific sites on the cell's DNA Activate genes that result in synthesis of new proteins. OVERVIEW ENDOCRINE SYSTEM - Network of ductless gland Devoid of ducts to carry products to the surface Directly secrete to the bloodstream Regulatory system 2nd messenger system of the body Uses chemical messages (Hormones) that are released into the blood Hormones control several major processes: 1. Reproduction 2. Growth and development 3. Mobilization of body defenses 4. Maintenance of much of homeostasis 5. Regulation of metabolism HORMONES Comes from a Greek word meaning "to arouse" Produced by specialized cells (secrete hormones into extracellular fluids) Blood transfers hormones to target sites. Once binding happen, hormones regulate the activity of OTHER CELLS Regulate the activity of other cells Chemical classification of hormones: ➢ ➢ ➢ ➢ SECOND-MESSENGER SYSTEM: NONSTEROID HORMONE MECHANISM ➢ ➢ - ➢ CONTROL OF HORMONE RELEASE ❖ ❖ ❖ ● ● ● Amino acid-based hormones (proteins, peptides, amines) Steroids (cholesterol) Prostaglandins (highly active lipids) ❖ Hormone levels in the blood are maintained by negative feedback. A stimulus/low hormone levels in the blood triggers the release of more hormones Hormone release stops once an appropriate level in the blood is reached Hormone levels is inhibited by hormone itself 3 STIMULUS MECHANISM OF HORMONE ACTION Hormones affect only certain tissues/organs (target cells or organs) ❖ Target cells must have specific protein receptors ❖ Hormone binding influences the working of the cells Effects caused by hormones: 1. Changes in plasma membrane permeability/electrical state 2. Synthesis of proteins, such as enzymes 3. Activation/inactivation of enzymes 4. Stimulation of mitosis 5. Promotion of secretory activity ❖ HORMONAL STIMULUS Prepared by:Jtablo - Utilized by steroid hormone - Action of hormones is directed to the nucleus where genetic material is stored. - Steroid hormone crosses the cytoplasm and once it enters the plasma - The hypothalamus secretes hormones that stimulate the anterior pituitary gland to secrete hormones that stimulate other endocrine glands to secrete hormones. - Endocrine glands are activated by other hormones Ex. Hypothalamus – secretes hormones that can stimulate the pituitary gland to release hormones that would signal the other gland (thyroid, adrenal and gonads) in the endocrine system. TWO TYPES OF MECHANISM DIRECT GENE ACTIVATION: STEROID HORMONE MECHANISM Most hormone utilized the 2nd mechanism Opposite of the previous mechanism Nonsteroid can only be in the plasma membrane Hormone binds to a membrane receptor & it does not enter the cell Sets off a series of reactions that activates an enzyme catalyzing a reaction that produces a second messenger molecule The receptor protein activates an enzyme, which produces the 2nd messenger. It promotes specific responses. Oversees additional intracellular changes to promote a specific respons. HUMORAL STIMULUS - Capillary blood contains low concentration of Ca, which stimulates secretion of parathyroid hormone (PTH) by parathyroid MT 201-BIOCHEMISTRY FOR MEDICAL LABORATORY SCIENCE LESSON: 2_FINALS THE ENDOCRINE SYSTEM FIRST SEMESTER | AY 2023-2024 glands. - Changing blood levels of certain ions stimulate hormone release Ex. Calcium Level – sensed by capillary gland, signals the parathyroid gland to secrete hormone to stabilize the calcium level. - Preganglionic sympathetic fiber stimulates adrenal medulla cells to secrete catecholamines; epinephrine and norepinephrine (Fight or Flight hormones). NEURAL STIMULUS HYPOTHALAMUS -2nd major - Neuroendocrine organ - Master of the master gland - Secretes releasing and inhibiting hormones - Hormonal release of the anterior pituitary is controlled by releasing hormone & inhibiting hormones produced by hypothalamus THYROID GLAND - Found at the base of the throat - Two lobes; Both are connected to the isthmus (bridge of tissues). Hormones: 1. Thyroid Hormone (Major metabolic hormones) ❖ T3/Triiodothyronine ❖ T4/Thyroxine Note: The number indicates the number of iodine present in the particular hormone. 2. Calcitonin – secreted by the parafollicular gland (c-cell. Involves in some calcium regulation. ENDOCRINE SYSTEM MAJOR ENDOCRINE GLANDS “Hypophysis” - Small gland (pea sized) - Hangs by a stalk from the hypothalamus - Protected by the sphenoid bone Has 2 functional lobes: PITUITARY GLAND Anterior pituitary/Adenohypophysis ❖ Glandular tissue ❖ "Master endocrine gland" ❖ All hormones are released here. ❖ Releases 6 hormones (2 affect non-endocrine targets & 4 stimulate other endocrine glands [tropic hormones]) ❖ Involves a secondary messenger. ❖ Proteins (or peptides) Act through second-messenger systems ❖ Regulated by hormonal stimuli, mostly negative feedback. Posterior pituitary ❖ Nervous tissue ❖ Storage area for hormones made by hypothalamic neurons. ❖ Nervous tissue and extension of the brain. ❖ Not an endocrine gland. Note: ❖ ❖ Prepared by:Jtablo Oxytocin - Acts on mammary and uterine gland Antidiuretic hormone (ADH) or vasopressin – decreases urination for the body to retain fluid. Acts on the kidney tubules. PARATHYROID GLANDS - Tiny masses on the posterior of the thyroid - Chief cells secrete parathyroid hormone (chemical class: peptide) ❖ Stimulate osteoclasts to remove calcium from bone ❖ Stimulate the kidneys & intestine to absorb more calcium ❖ Raise calcium levels in the blood Main Function: Calcium regulation (more efficient than calcitonin) Ad – adjacent Renal – Kidneys - Triangular shaped - Two small glands located superior/top of the kidney ADRENAL GLANDS TWO GLANDS: ❖ Adrenal Medulla - Inner neural tissue region; produces catecholamines (epinephrine & norepinephrine) ❖ Adrenal Cortex - outer glandular region; produces 3 major groups of steroid hormones (corticosteroids) MT 201-BIOCHEMISTRY FOR MEDICAL LABORATORY SCIENCE LESSON: 2_FINALS THE ENDOCRINE SYSTEM FIRST SEMESTER | AY 2023-2024 Endocrine – Islets (Little masses/portion) - 5-6 inches in length - Secretes hormones - Curved of duodenum - Protein in nature Hormones: ❖ Insulin ❖ Glucagon ❖ Somatostatin These three functions in glucose levels. Other Hormones: ❖ Androgens (most common is testosterone) ❖ Estrogen ❖ Aldosterone – helps regulate blood volume, blood pressure, and levels of Na, K, and H in the blood. Process: Cell Types in the Pancreatic Islets 1. Alpha (A) cells ➔ 17% of pancreatic islet cells & secrete glucagon that acts on tissue to form energy (glycogen). ➔ Lead to increase blood glucose level. 2. Beta (B) cells ➔ 70% of pancreatic islet cells & secrete insulin that causes the entry of glucose in the cell ➔ Decreases blood glucose level. ➔ A Hypoglycemic agent. 3. Delta (D) cells ➔ 7% of pancreatic islet cells & secrete somatostatin. Controls the production of insulin and glucagon via paracrine action. ➔ Paracrine action, binding of release hormones to adjacent cells. ➔ Inhibits the release of insulin and glucagon. Regulatory hormones. 4. F cells ➔ 6% of pancreatic islet cells & secrete pancreatic polypeptide. ➔ Stimulate the activity of gastric chief-cells and inhibits bile secretions Notes: Renin - produced by juxtaglomerular cells from the kidney. Angiotensinogen - secreted from the liver ❖ PANCREATIC ISLETS Release of angiotensin 1 activated by ACE from the lungs converts angiotensin 1 to 2 in order to function for the release of aldosterone. Pancreas is a mixed gland ❖ Flattened organ that measures about 12.5-15 cm (5-6 in.) in length, located in the curve of the duodenum. ❖ Functions as exocrine and endocrine glands Pancreatic islets (islet of Langerhans) ❖ Chemical class: protein ❖ Little masses of hormone-producing tissue scattered among the enzyme-producing acinar tissue of the pancreas Exocrine - Acinar (Big portion) -Secretes digestive enzymes (amylase and lipase) Prepared by:Jtablo PINEAL GLAND - A small, pine/cone-shaped gland found hanging from the roof of the 3rd ventricle of the brain. - Secretes melatonin ❖ Chemical class: amine ❖ Contribute to the setting of the body's biological clock ❖ Peak levels is at night & lowest levels MT 201-BIOCHEMISTRY FOR MEDICAL LABORATORY SCIENCE LESSON: 2_FINALS THE ENDOCRINE SYSTEM FIRST SEMESTER | AY 2023-2024 is during daylight (noon) May have other as-yet-unsubstantiated functions Hormones: ❖ Melatonin - Amine that contributes to the body's biological clock. - Peak: High at night - Lowest: Daytime (noontime) OTHERS: ❖ Unsubstantiated Action: Was believe to decrease the LSH and FSH, which inhibits the production of reproductive system THYMUS GLAND - Located posterior to the sternum, between the lungs, adjacent to the heart - Unique since it is largest in infants & children but decreases in size as we age. - Produces thymosin ❖ Chemical class: peptide ❖ Promotes maturation of some types of WBCS ❖ May retard aging process ❖ Important in developing the immune system PLACENTA Hormone: Thymosin – Maturation of wbc in developing the immune system. May retard the aging process. KIDNEY - Produce sex cells and sex hormones that are identical to those produced by adrenal cortex cells GONADS Prepared by:Jtablo Two Components: 1. Ovaries ➔ Estrogen and Progesterone Females produces that affects the sexual characteristics 2. Testes ➔ Testosterone Produced by male that affects their sexual characteristics Note: Main sex hormone: Testosterone Androgen: General term for hormones that contribute to growth and reproduction in both men and women. OTHERS: Produces: ❖ Human chorionic gonadotropin (hCG) ➔ Stimulates corpus luteum in the ovary to continue production of estrogens & progesterone to maintain pregnancy. ❖ Estrogen & progesterone ➔ Maintain pregnancy; help prepare mammary glands to secrete milk. ❖ Human placental lactogen (hPL) ➔ Works cooperatively with estrogen & progesterone in preparing the breasts for lactation ❖ Relaxin and Oxytocin ➔ For the peace in giving birth ➔ Causes the mother's pelvic ligaments & the pubic symphysis to relax & become more flexible, which eases birth passage Note: Oxytocin is released from the posterior pituitary gland Produces: Erythropoietin - stimulates the production of RBC in the bone marrow during hypoxia. MT 201-BIOCHEMISTRY FOR MEDICAL LABORATORY SCIENCE LESSON: 2_FINALS THE ENDOCRINE SYSTEM FIRST SEMESTER | AY 2023-2024 MOST COMMON DISORDERS - Imbalances are caused by: ➔ Hyposecretion (decrease) and hypersecretion (increase) ➔ Faulty hormone receptors ➔ Defect in 2nd messenger system ➔ Inadequate number of receptors. DIABETES INSIPIDUS ❖ Excessive urine output due to hyposecretion of ADH ❖ People are continually thirsty & drink huge amounts of water. ❖ Was called diabetes due to its cardinal signs. Cardinal Signs: ➔ Polyuria – Excessive urination ➔ Polydipsia - Excessive drinking of water PITUITARY DWARFISM ❖ Hyposecretion of GH during childhood slows bone growth, & the epiphyseal plates close before normal height is reached. GIGANTISM ❖ Hypersecretion of GH during childhood, an abnormal increase in the length of long bones Acromegaly: ➔ Hypersecretion of GH occurs after long-bone growth has ended. Occurs in adults, certain parts elongate. STERILITY ❖ Hyposecretion of FSH or LH in both males and females ❖ Decrease concentration or secretion in the reproductive system. ❖ No fertilization (pregnancy) Note: Luteinizing hormone (LH) plays a key role in gonadal function. LH in synergy with follicle stimulating hormone (FSH) stimulates follicular growth and ovulation. GOITER ❖ Enlargement of thyroid gland that results when the diet is deficient in iodine. ❖ Since no metabolic hormones will be secreted. ❖ Common CRETINISM ❖ Congenital hypothyroidism ❖ Hyposecretion of thyroid hormones that is present at birth, causes severe mental retardation & stunted bone growth ❖ Part of the newborn screening is the hormonal imbalances. MYXEDEMA ❖ Hypothyroidism occurring in adults ❖ Occurs 5x more often in females. Hallmark: edema (Mucus swelling) Prepared by:Jtablo GRAVES' DISEASE ❖ Most common form of hyperthyroidism ❖ Autoimmune disorder in which the person produces antibodies that mimic the action of TSH Clinical manifestation: ➔ Enlarged thyroid ➔ Exophthalmos (protruding eyes) HYPOPARATHYROIDISM ❖ Too little parathyroid hormone-leads to a deficiency of blood Ca2+, leading to twitches, spasms, & tetany of skeletal muscle ADDISON'S DISEASE ❖ Hyposecretion of glucocorticoids & aldosterone ❖ Majority of cases are autoimmune disorders, characterized by a peculiar bronze tone of skin HYPER- ALDOSTERONISM ❖ Overproduction of the hormone aldosterone by adrenal glands ❖ Excessive water & sodium are retained, leading to high blood pressure & edema. CUSHING'S SYNDROME ❖ Hypersecretion of cortisol by the adrenal cortex ❖ Causes include a tumor of the adrenal gland that secretes cortisol, or a tumor elsewhere that secretes ACTH, which in turn stimulates excessive secretion of cortisol. ❖ “Hypercortisolism” Clinical manifestation: ➔ Swollen moon shaped face ➔ Redistribution of fat in the abdomen and posterior neck (Buffalo hump) ➔ Easily bruised and poor wound healing MASCULINIZATION ❖ Hypersecretion of the sex hormones, regardless of sex ❖ In females: beard develops & masculine pattern of body hair distribution occurs DIABETES MELLITUS ❖ Inability to produce/use insulin ❖ Blood glucose level is high & glucose "spills" into the urine (glucosuria) Hallmarks: ➔ Polyuria - Excessive urination ➔ Polydipsia - Excessive drinking of water ➔ Polyphagia - Excessive hunger, leads to excessive eating HYPERINSULINISM ❖ Often results when a diabetic injects too much insulin Main symptom: ➔ Hypoglycemia - blood sugar (glucose) level is lower than the standard range.
