The Endocrine System Dr. Tamie Lieto

Endocrine Endo=within Krino= separate The word implies that intercellular chemical signals are produced within and secreted from endocrine glands, but that the chemical signal have effects at locations that are away from or or separate from the endocrine glands that secrete them. The chemical signals are transported by way of the blood

Hormones Hormones – the intercellular chemical signals that are secreted by the endocrine glands Hormone means “set in motion” because hormones set things in motion Hormones are distributed in the blood to all parts of the body BUT only certain tissues called Target tissues respond

Regulation of Hormone Secretion Negative Feed Mechanism based on the following: blood levels of chemicals eg glucose and insulin hormones eg some hormones control other hormones Nervous System eg epinephrine is released from adrenal medulla because of nervous stimulation

Endocrine Glands and Their Hormones Look at Table 10.3 Endocrine Glands, Hormones and their Target Tissues

Classification of Hormones Proteins/ Amino Acids thyroid posterior pituitary Lipids Steroids Eicosanoids

Pituitary Gland The pituitary gland is located posterior to the optic chiasm and beneath the hypothalamus. It is connected to the hypothalamus by a stalk called the infundibulum It is divided into anterior and posterior parts It is part of the Hypothalamus Pituitary Axis

Pituitary Gland

Pituitary The Pituitary Gland is divided into Anterior and Posterior Parts Hormones from the pituitary control control the function of many other endocrine glands such as the ovaries , testes, thyroid gland and adrenal coortex Also secretes hormones that affect growth, kidney function, birth and milk production by the breast Release of Hormones from the Pituitary is under the control of the Hypothalamus

Hormones secreted by the Pituitary Growth Hormone- stimulates growth of bone and organs by increasing protein synthesis It resists protein breakdown during food deprivation and promotes fat breakdown instead Growth hormone is under the control of Growth hormone releasing factor (GHRF) and Growth Hormone Inhibiting Factor)

Hormones secreted from the pituitary gland AnteriorPituitary Posterior Pituitary Antidiuretic Hormone Growth Hormone Oxytocin Thyroid stimulating hormone (TSH) Adrenocorticotrophic hormone ( ACTH) Melanocyte Stimulating hormone Luteinizing Hormone Follicle Stimulating Hormone Prolactin

Growth Hormone (GH) Growth Hormone- increases protein synthesis and growth of tissue and organs, breakdown of lipids, and release of fatty acids, increase blood glucose levels Target Tissue : Most Tissue

Deficient of Growth Hormone Pituitary Dwarfism

Excess Growth Hormone Gigantism Exces growth hormone can result from hormones secreting tumors of the pituitary gland

Acromegaly IF growth hormone continues to be in excess after the growth plates are closed bones will grow wider . This condition is called acromegaly

Thyroid Stimulating Hormone (TSH) Target tissue: binds to the receptors on the thyroid gland and causes the thyroid gland to secrete thyroid hormone Too much TSH over stimulates the Thyroid gland ( enlarges) Too little TSH under stimulates the Thyroid gland (Shrinks) TSH is under the control of the Thyroid Releasing Hormone released form the hypothalmus

Adrenocorticotropic Hormone ACTH Target Tissue: Binds to receptors on the adrenal cortex gland and stimulates release of the Glucocorticoid hormones such as cortisol Target Tissue: Binds to melanocytes in the skin and increase skin pigmentaion ACTH is under the control of the ACTH releasing hormone secreted by the hypothalmus

Gonadotropins Target Tissue: Bind to the receptors on the gonads(ovaries and testes) Luteinizing Hormone Follicle Stimulating Hormone Under control by the GNRH or gonadotropin releasing hormones of the hypothalamus

Luteinizing Hormone (LH) Females- target tissue ovary, promotes ovulation and progesterone in the ovary Males- target tissue testis, causes testosterone synthesis and supports sperm cell production in testis t

Follicle Stimulating Hormone (FSH) -Female Target tissue :Follicles in ovary. Promotes follicle maturation and estrogen secretion in ovary. - Male Target tissue- Seminiferous tubules in male causing Sperm production

Prolactin Female- Target Tissue: receptors in the breast and ovary Helps promote breast development during pregnancy and stimulates the production of milk. Prolongs progesterone secretion following ovulation and during pregnancy. Male - Target tissue-testis increses sensitivity to LH Under control of the releasing hormones from the hypothalamus

Site of Prolactin Action is the Mammary Gland

Melanocyte Stimulating Hormone (MSH) Target Tissue: MSH binds to receptors on the skin and increase the production of melanocytes causing them to synthesize melanin Causes the skin to darken Under the control of releasing hormones that increase or decrease its production

Antidiuretic Hormone ADH Target Tissue: binds to receptors in the kidney that increase water reabsorption by kidney tubules. This results in less water loss as urine.

Oxytocin Target Tissue: Binds to membrane bound receptors in uterus and mammary glands. Causes contraction of the smooth muscle in the uterus and milk let down in breast

The Thyroid made up of two lobes connected by a narow band called the ithmus lobes are on either side of the trachea highly vascular contains follicles filled with the protein hormone Secretes Thyroid Hormone

Thyroid Hormone Target Tissue : most cells of the body regulates your rate of metabolism also important for growth and development The thyroid gland requires iodine to synthesize thyroid hormone deficiency of iodine in the diet can lead to thyroid hormone deficiency regulation is through feed back mechanism Fig10.14

Hypothalamus-Pituitary- Thyroid Axis

Lack of thyroid hormone is called Hypothyroidism

Excess amout of thyroid hormone can lead to GRAVES DISEASE

Parathyroid Gland Four glands that are embedded in the posterior wall of the thyroid Secretes Parathyroid hormone Calcitonin hormones which regulates calcium metabolism

Parathyroid Hormone Target tissue : bone and kidney PTH binds to membrane bound receptors of cells and increases the absorption of calcium from the intestines which increases active Vitamin D PTH also causes the resorption by incresing the rate of bone breakdown by osteoclasts of bone tissue to release Ca (calcium) into the circulation and decreases the rate at which Ca is lost in the urine PTH acts on tissue to raise blood Calcium Levels to normal

Calcitonin Target Tissue – Bone Decreases the rate of bone breakdown, prevents large increase in blood calcium levels following a meal

Adrenal Gland Divided into Adrenal Cortex (outer) Glucocorticoids (cortisol) Aldosterone Adrenal Androgens Adrenal Medulla Epinephrine and Norepinephrine

Layers of the Adrenal Gland

Arenal Cortex Hormones Mineralocorticoids- Aldosterone – regulation of NA and K and water balance. Glucorticoids- Cortisol – decreases inflammation, increases glucose Adrenal Androgens DHEA- axillary and pubic hair in females

Excess Adrenal Androgens (DHEA) in females

Cushing Syndrome ( excess cortisol)

The Pancreas Both Endocrine and Exocrine Gland The Endocrine part pancreatic Islets which secrete insulin (beta cells) glucagon( alpha cells)

Pancreatic Islet cells

Blood Glucose control Under the control of insulin and glucagon It is very important to maintain blood glucose levels within a normal range of values. A decline in blood glucose level below its normal range causes the nervous system to malfunction because glucose is the nervous system’s main source of energy

Insulin Insulin is released from the beta cells primarily in response to the elevated blood glucose levels and increased parasympathetic stimulation that is associated with the digestion of a meal. Increased blood levels of certain amino acids also stimulate insulin secretion. Decreased insulin secretion results from decreasing blood glucose and from stimulation by the sympathetic division of the nervous system This allows blood glucose to be conserved to provide the brain with glucose.

Glucagon Binds to receptors on liver cells and causes the release of glucose from glycogen The glucose is then released in the blood to increase blood glucose levels Glucagon secretion is reduced after a mealb

Diabetes Mellitus Two Types Type I - secretion of too little insulin from the pancreas - onset childhood, very thin , require insulin Type 2 - insufficient numbers of insulin receptors on target cells or defective recepetors - adult onset, usually overweight, can take medications that help increase endogenous insulin activity.

Diabetes Mellitus Type I The signs and symptoms As a result, tissues can not take up glucose and the blood becomes Hyperglycemic Satiety center responds as if there is no glucose and patients feeel hungry Excess glucose is secreted in urine and they become dehydrated Fats and protein become energy source and body wasting occurs

Table 10.4 Effects of Insulin and Glucagon on Target Tissue

Testes and Ovaires Testes secrete testosterone- growth of male and development of male reproductive structures, muscle enlargement, hair, voice change and male sexual drive Ovaries secrete estrogen and progesterone- female characteristics Both are under control of FSH and LH form the pituitary

Pineal Gland Small gland superior and posterior to the thalamus Secretes a hormone called melatonin which decreases LH and FSH by decreasing GNRH which may help regulate the onset of puberty by acting on the hypothalmus

Thymus Secretes thymosin which enhances the ability of the immune system Thymosin helps in the production of the white cells ( called T cells)

Other Hormones Prostaglandins- role in inflammation Erythropoietin-comes from kidney and stimulates red blood cell production HCG ( human chorionic gonadotropin) – secreted by the placenta during pregnancy to maintain the pregnacy.

Age Related Changed in the Endocrine System Age related changes include a gradual decrease GH inpeople who do not exercise Melatonin Thyroid Hormone Reproductive Hormones Thymus Hormones Increase in Diabetes