Endocrine System PDF

Endocrine System Karen Gil MD, MHSN Objectives 1. Provide an overview of what the endocrine system, his components, and its role in maintaining homeostasis 2. Explain the function of hormones in the body, including how they are produced, released, and their target organs or tissues 3. Discuss the ma...

Endocrine System Karen Gil MD, MHSN Objectives 1. Provide an overview of what the endocrine system, his components, and its role in maintaining homeostasis 2. Explain the function of hormones in the body, including how they are produced, released, and their target organs or tissues 3. Discuss the major endocrine glands, detailing their structure and primary hormones 4. Describe the mechanisms of hormonal regulation, including feedback loops and the role of hypothalamus-pituitary axis 5. Discuss common disorders of the endocrine system, specifically at the anterior pituitary gland and their association with eye diseases and treatment Endocrine System The nervous and endocrine systems act together to coordinate functions of all body systems The endocrine system controls body activities by releasing mediator molecules called hormones Hormones are released in one part of the body but regulates the activity of cells in other parts of the body Nervous and Endocrine System Nervous system Endocrine system Neurotransmitter are the mediator molecules Locally released in response to nerve impulses Site of action close to the site of released fast travel Target cells are muscle, cells, glands, neurons Time of onset of action milliseconds Duration of action milliseconds Hormones are the mediator molecules Delivered to tissues throughout the body by the blood Site of action far from site of released up tours Target cells are cells throughout the body Time to onset of action seconds to hours or days Duration of action seconds to days · can take. Endocrine Glands Function Help regulate– – – – Chemical composition and volume of interstitial fluid Metabolism and energy balance Contraction of smooth and cardiac muscle fibers Glandular secretions and some immune system activities thyroidgland (T33TH) – Control growth and development Humangouth – Regulate operation of reproductive systems Gonadotrophs – Help establish circadian rhythms ex : homore in children : eX : ex Endocrine System Two kinds of glands – Exocrine glands Secrete their products into ducts that carry the secretions into body cavities, into the lumen of an organ or to an outer surface of the body – – – – Sudoriferous glands Sebaceous glands Mucous glands Digestive glands motility [prod. Hel – Endocrine glands Secrete their products into the interstitial fluid surrounding the to enter bloodstream secretory cells rather than into ducts Circulating blood delivers the hormones to target tissues Endocrine System Endocrine Glands: – – – – – Pituitary works w/hypothalamus Thyroid located neck (coundt ↓ metabolicactivity/ Parathyroid 4 glands locatedbehind thyroid Adrenal located top of kidneys prod grocorticoids (important a Pineal glands or in ~ on fo ~ CNS , behind hypothalamus Organs that contain cells that secrete hormones – – – – – – – – – – – – – Hypothalamus Thymus (Myasthenia Mavis) disappear during of Pancreas polypeptide FHEFSH Ovaries production of Testes plod, of spam Kidneys eythropoietin enythrocytes Stomach gastrin Liver pod. of growth protein important Small intestine produce Skin of melanocytes Heart lipids energy Adipose tissue Placenta important of passage proteins during pregnancy - adolescent should ~ T production insulin cells , ovals , - secutin cholesteral stimulation , in Human to breakdown Melanin to make lives All endocrine glands and hormonesecreting cells constitute the endocrine system Hormone ~ ~ cannot emit an autoimmune 50 hormones Affect only target cells * binding to specific receptors e specific organ Endocrine secretion alters the physiologic activity of target cells Powerful effect even at low concentrations Target cells can have 5,000 to 100,000 receptor for a particular hormone action e diseases a appear diff. cell wo wo the a receptor receptor Functional Types Endocrine most common ↑ Circulating Secrete hormone e travel Autocrinecell? make action e ~ through specific cell for it to far bloodstreamto travel specific in same cell Paracrine short distance , neighbor Local 2 cell Types of local hormones Paracrines Act on neighboring cells Autocrines Act on the same cell that produce them Hormone Interactions Responsiveness of a target cell to a hormone depends on: 1. Hormone concentration 2. Abundance of the target cell’s hormone receptors if receptor 3. Influences exerted by other hormones no , will not make action eX' ~ - autoimmune diseases thatworktogether/stop response glucagon & insWin hypoglycemia work together to or hypoglycemia prevent Control of Hormone Secretion Regulated by: 1. Signals from CNS 2. Chemical changes in blood 3. Other hormones Most systems that regulate secretion of hormones work by – Feedback mechanism positive (stimulating secretion) negative (inhibiting secretion) most common * Feedback Mechanism Hormone level low or hormone required Negative feedback mechanism – Works when high levels of a hormone in question turns off its own secretion – Controlled by hypothalamus or pituitary gland Hormone released Blood hormone levels become high Hypothalamus releases inhibitory hormone or hypothalamus and/or pituitary secretions stopped Feedback Mechanisms Positive Feedback – results in amplification of the stimulus and increased release of the hormone involved until a particular process is complete ~ Hormone required and released Process stimulated and hormone release continues during laber , sends signal to pit. gland then to muscle to make contractions · oxytocin continuously made until to get baby out is contract muscles Process complete Hormone release stop Hypothalamus center Important regulatory center for the Nervous and Endocrine Systems Hormones secreted by the hypothalamus and the Pituitary Gland regulate: – virtually all aspects of growth, development, metabolism and homeostasis of - brain Hypothalamic Hormones only 2 inhibiting Negative ~ GHRH hormones – Growth hormone releasing hormone stimulate inhibit N GHIH – Growth hormone inhibiting hormone) TRH elit a stimulus to pit. gland to produce TSH by thyroid – Thyrotropin releasing hormone GnRH sex produced by pit. gland – Gonadotropin releasing hormone PRH – Prolactin releasing hormone ↓ PIH – Prolactin inhibiting hormone CRH. thyroid stim hormone prod. of mith hamenes ACTH : > glucocorticosteroids advenal gland - – Corticotropin releasing hormon PRI growth homore feedback controls the other most important in babies & adoles. 2: : Pituitary Gland Anatomically rest on the sphenoid bone (sella turcica) in the cranial vault 1-1.5 cm Connected by the infundibulum to the of diff hypothalamus Histologically is divided into three lobes but functionally into two lobes D allows 1. 2. 3. passage. oculomoto trocklea trigeminal Vessels Adenohypophysis (anterior lobe) 75 % Pars intermedia (intermediate lobe) Neurohypophysis (posterior lobe) ↑ pass · media no generation of hormone , just divides it Pituitary Gland Adenohypophysis Produces 7 hormones: hGH - human Growth Hormone produced in anterior on pituitary gland ACTH - Adrenocorticotropic hormone minimum adrenal contex - important for prod of glucocorticoids TSH -Thyroid-stimulating hormone NTT4 PRL - Prolactin goes to breast to produce with who ejects/contracts ? Oxycitin MSH - Melanocyte-stimulating you're exposed hormone Stimulated when Gonadotropins sexual hormones ▪ FSH - Follicle-stimulating hormone ▪ LH - Luteinizing hormone to run GH (something) Pituitary Gland Neurohypophysis Produce 2 hormones ADH - Antidiuretic hormone or vasopressin during Oxytocin labor stimulated ~ ~ highest amounts when baby is during labor getting breastfed anterior m nuclei. of hypoth to hypothalamus Histology of the Adenohypophysis all are located in pituitary gland Somatotrophs – Produce human growth hormone (hGH) pituitary gland – stimulating general body growth and regulating aspects of metabolism Canterio Thyrotrophs – Produce thyroid stimulating hormone (TSH) – involved in control of secretion and other activities of the thyroid gland T3ET Histology of the Adenohypophysis Gonadotrophs cells that produce (I/FSH lovaies/testes) – Produce and release follicule stimulating hormone (FSH) and lutenizing hormone (LH) Together stimulate secretion of estrogen and progesterone stimulating oocyte maturation in the ovaries and production of sperm in the testes Histology of the Adenohypophysis Lactotrophs – Synthesize prolactin (PRL) production of – initiates milk production by mammary glands milk Corticotrophs – Produce adrenocorticotropic hormone (ACTH) and melanocyte-stimulating hormone – which stimulates the adrenal gland to secrete glucocorticoids Control of secretion by the Anterior Pituitary Regulated in two ways 1. Neurosecretory cells in the hypothalamus secrete releasing and inhibiting hormones 2. Negative feedback inhibits – Rising blood levels of hormones released by target glands decrease secretions of some anterior pituitary cells http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter20/ani mation__hormonal_communication.html Control of secretion by the Anterior Pituitary * Hormone Secreted by Releasing hormone Inhibiting hormone Somatotrophs GHRH GHIH Thyrotrophs TRH GHIH Gonadotrophs GnRH - LH Gonadotrophs GnRH - PRL Lactotrophs PRH PIH ACTH Corticotrophs CRH - Corticotrophs CRH Dopamine hGH human Growth Hormone TSH nating FSH MSH Sing ice Melanochea Harmant low amounts will elicit of dopamine of MSH response Control of secretion by the Anterior Pituitary Human Growth Hormone (hGH or Somatotropin) Most abundant hormone of the anterior lobe It is released every 2 hours It promotes cell growth and regulates metabolism Human Growth Hormone (hGH or Somatotropin) DIRECT ACTION Stimulates protein synthesis Promotes synthesis of small proteins that are powerful insulin-like growth factors (IGF’s or somatomedins) - – Mainly produced by the liver * Human Growth Hormone (hGH or Somatotropin) INDIRECT ACTION Stimulates lipolysis (breakdown of triglycerides into fatty acids and glycerol) energy – for ATP production through fatty acids oxidation Also stimulates glucose release from the liver (insulin antagonist or diabetogenic effect) DIc it ↑ glucose in blood Human Growth Hormone (hGH or Somatotropin) REGULATION MECHANISM Mainly controlled by 2 hypophysiotropic hormones – GHRH (growth hormone releasing hormone) – GHIH (growth hormone inhibiting hormone) Major regulator of GHRH and GHIH secretion is blood glucose level Other factors which promote secretion includes – – – – – Decreased fatty acids increased amino acids proteins sleep helps stimulating growth deep sleep size stress or vigorous exercise other hormones as glucagon, estrogen, cortisol and insulin = Dic in babies , too much for nomone to increasein Hypothalamus is stimulated to secret GHRH during hypoglycemia and GHIH during hyperglycemia 790 mg < 100 mg Follicle Stimulating Hormone (FSH) Women Stimulates development of follicles for secretion of estrogen - ovulation Men Stimulates production of sperms Luteinizing Hormone LH In females together with FSH stimulates secretion of estrogen and bring about ovulation Also stimulates the formation of the corpus luteum (structure formed after ovulation) in females – in the ovary and produces progesterone – This help in the preparation of the uterus for implantation of a fertilized ovum as well as mammary gland for milk secretion In males stimulates the interstitial cells to secret large amounts of testosterone Regulation mechanism GnRH release is under a negative feedback http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter20/animation__posi tive_and_negative_feedback__quiz_1_.html Gonadotropins FSH and LH the FSH stimulated for prod. of ↑ degladation of ovale progesterone is ovale L I prepares for pregnancy after follicular phase Prolactin Together with other hormones initiate and controlled by presence of maintain milk secretion exytocin by the mammary gland Ejection of milk depends on oxytocin raise during pregnancy Sucking of the infant reduces the hypothalamic secretion of PIH – Increase prolactin secretion (PRH elevated) Prolactin increases ~ during whole pregnancy with to preparing the · contractions breast of eject uterus also ↑ help Regulation – The hypothalamus secretes Stimulating hormone - PRH (prolactin-releasing hormone) inhibitory hormones – PIH (prolactin-inhibiting hormone) PIH diminish before menstruation and prolactin rises, as the menstrual cycle begins new PIH increase and prolactin decrease of breastfeeding after momschoose Prolactin levels ~ this may occur bl 1 y10 , to stop breastfeeding for a childe Lyo X should stop e yoo Endocrine Disorders Disorders results form – Dysfunction originating in the peripheral endocrine gland itself (primary disorders) – Understimulation or overstimulation by the pituitary (secondary disorders) Overproduction (hyperfunction) Underproduction (hypofunction) HYPERSECRETION – Functional Adenoma HYPOSECRETION – – – – Ischemic damage Inflammation Radiation Non-functional adenomas Pituitary Adenoma lactotrophs Pituitary Adenomas Prolactinoma Most common type of benign tumors Lactotroph cells secrete prolactin nasal Fibers decussate temporal – High prolactin levels (hyperprolactinemia) ~ chances in menstrual cycle , women who ar producing mithw/o pregn., Characterized by – – – – – – – Headaches ceubrospinal Amenorrhea Galactorrhea Loss of libido or impotence Infertility blcof ovulation Visual disturbances Visual field defect 42) fluid ncreases no bitemporal hemaniopeia Lab test (look slide – High Prolactin levels – Low FSH and LH men who lactate Pituitary Adenomas Si ↑ temporal fibers Pituitary Adenomas Head MRI Visual Field Pituitary Adenomas Treatment – Macroadenomas >10mm Surgery – Microadenomas < 10 mm Dopamine agonists control prolactin release Cabergoline 0.5mg (Dostinex) – QD or BID Bromocriptine 2.5mg (Parlodel) – BID or TID Pituitary Adenomas Growth-hormone-producing adenoma Elevated growth hormone (GH) Elevated somatomedin C or IGF-1 – GIGANTISM – ACROMEGALY excessive GH Pituitary Adenomas Gigantism Occurs in children and adolescent's prior fusion of the growth plates Hypersecretion of GH Characterized by closure - – symmetrical increase in stature and visceral enlargement Dx. – GH quantification ( > GH) E Pituitary Adenomas flathead big S [ nose mandible is Acromegaly Functional adenoma – organs can grow in size bigge (bign) M Hypersecretion of GH during adulthood big hands Physical findings – – – – – – Coarse facial features Prominent jaw Flat, broad forehead Enlarged hands and feet Broad fingers and toes Headache and visual field defects (bitemporal hemianopsias) Enlarged sella turcica Internal organs enlarged Most common cause of death is cardiac failure Dx: – excessive GH enlarged Tx. – sella tucica GH quantification ~ enlargement of Surgery ~removal ~ feet Pituitary Adenomas Acromegaly Pituitary Adenomas Hypopituitarism Destructive lesion of Pituitary gland (75% of parenchyma) result in panhypopituitarism Characterized – Thyroid, adrenal gland and reproductive organs abnormalities Common causes 1. Adult Pan-hypopituitarism – Expansile pituitary tumors 2. Sheehan’s Syndrome ischemia of ea – Postpartum necrosis of the pituitary gland during pregnancy , high BP blc of predampsia ↓ prod of. GH nomenstru elbradycardia , loss of hair ,.) a sexual orient Pituitary Adenomas Panhypopituitarism Tx. Hormone replacement Pituitary Insufficiency in Children In most cases no lesions are identified Other causes is a Craniopharingioma – Most common manifestation is dwarfism – Rare – Characteristics Headache 60-80 % ↓ of intracranial pressure (iictsvoitway) Vomiting (projectile vomiting) 35-70 % Vision loss – 20-60 % – Anterior extension to the optic chiasm result in bitemporal hemianopsia, unilateral temporal hemianopsia, papilledema or decrease in visual acuity unilateral or bilateral Endocrine dysfunction – Tx. Surgery removal of Humor all homones should be quantified Pituitary Adenomas Carcinoma Pituitary Carcinoma Exceedingly rare tumors only diagnosed after metastasis has occur – mostly from breast, lung, renal, prostate, and colon cancers Surgical Removal of Pituitary Tumors Endoscopic skull base surgery Open Craniotomy