Intro. to Endocrinology

Endocrine Gland
a ductless glad that secretes hormones directly into the blood stream.
Endocrine Hormone
a chemical substance produced by an endocrine gland, once released they bind to a target organ cell.
Exocrine Gland
secretes its product via a duct onto laminal surface
Target Organ/Cells
cell having a specific receptor that reacts with a specific hormone, antigen, antibody, antibiotic, sensitized T cell, or other substance.
Second Messenger
intracellular signals acting at or situated within the plasma memrane and translating electrical or chemical messages from the environment into cellular responses.
Autocrine Signaling
form of hormonal signaling in which a cell secretes a hormone, called the autocrine agent, that binds to autocrine receptors.
Paracrine Signaling
hormone function in which a hormone synthesized binds to its receptor in nearby cells and affects their function. Not released into the bloodstream, but into the surrounding tissues.
Endocrine Signaling
signaling in which endocrine cells release hormones that act on distant target cells.
a chemical substance that is produced and secreted into the blood by an organ or tissue, and has a specific effect on target tissue.
General Description of the Hypothalamus
Located inferior and to the thalamus & just above the brain stem. Receive input from other regions of the brain, the internal orans, and the visual system.
Function of the Hypothalamus
controls body temperature, hunger, thirst, fatigue, anger, circadianc ycles and helps control sexual behavior and defensive reactions such as fear and rage.
General Description of the Pituitary Gland
a pea sized structure attached to the bottom of the hypothalamus. Divided into two lobes, anteror and posterior.
Function of the Pituitary Gland
secretes hormones regulating homeostasis.
What 9 hormones does the hypothalumus produce?
Gonadotropin Releasing Hormone (GnRH)
Thyrotropin Releasing Hormone (TRH)
Corticotropin Releasing Hormone (CRH)
Prolactin Inhibiting Hormone (PIH)
PRolactin Releasing Hormone (PRH)
Melanocyte Stimulatin Hormone Inhibitin Factor (MIF)
MElanocyte Stimulating Hormone Releasing Factor (MRF)
GRowth Hormone Inhibiting Hormone (GHIH)
Growth Hormone Releasing Hormone (GHRH)
Gonadotropin Releasing Hormone (GnRH)
stimulates the release of the follicle stimulating hormone(FSH) and leutinizing hormone(LH).
Thyrotropin Releasing Hormone (TRH)
Thyrotropin Releasing Hormone (TRH)
stimulates the release of thyroid stimulatin hormone (TSH) and prolactin.
Corticotropin Releasing Hormone (CRH)
hormone & neurotransmitter involved in stress response. Stimulates the secretion of adrenocorticotropin (ATCH)
Prolactin Inhibiting Hormone (PIH)
inhibits prolactin production. inhibits milk production at the mammary gland.
Prolactin Releasing Hormone (PRH)
stimulates prolactin PRoduction
Melanocyte Stimulating Hormone inhibiting FActor (MIF)
inhibits melanocytes stimulating hormone (MSH) production
Melanocyte Stimulating Hormone Releasing Factor (MRF)
incluences melanocyte stimulating hormone (MSH) production.
Growth Hormone Inhibiting Hormone (GHIH)
also called somatostatin (SS) hormone. inhibits the secretion of Human Growth Hormone (hGH)
Growth Hormone Releasign Hormone (GHRH)
also called Somatocrinin-Hormones that stimulates Human Growth Hormone (hGH).
What are the hormones produced by the anterior pituitary?
Follicle Stimulating Hormone (FSH)
Leutinizing Hormone (LH)
PRolactin (PRL)
Thyroid Stimulating Hormone (TSH)
Adrenocorticotropic Hormone (ACTH)
Human Growth Hormone (hGH)
Melanocyte Stimulating Hormone (MSH)
Follicle Stimulating Hormone (FSH)
regulates the development, growth, onset of puberty, and reproductive processes of the human body.
Leutiniing Hormone (LH)
essential for reproduction.
Prolactin (PRL)
primarily associated with lactation
Thyroid Stimulating Hormone (TSH)
regulates the endocrine function of the Thyroid gland.
Andrenocorticotropic Hormone (ACTH)
stimulates the cortex of the adrenal gland, boosts synthesis of corticosterodis and sex steroids. related to the circadian rhythm in many organisms.
Human Growth Hormone (hGH)
stimulates growth and cell reporduction in humans.
Melanocyte Stimulating Hormone (MSH)
stimulates the production and release of melanin in skin and hair. When released in the brain it has an effect of appetite and sexual arousal.
How are the anterior pituitary hormones controlled?
through negative feedback from the target gland as well as hypothalimic releasing and inhibiting hormones.
How does hGH affect metabolism?
Promotes protein anabolism. Promotes lipid mobilization and catabolism. Inditectly inhibits glucose metabolism.
Stimulators for release of hGH
GHRH, deep sleep, hypoglycemia, exercise, elevation of amino acids, stress, high levels of insulin.
Inibitors of hGH release
hyperglycemia, GHIH, obesity, increased glucocotricoids.
hypersecretion of hGH, abnormal rapid rate of skeletol growth in childhood, height of up to 8 feet.
hypersecretion of hGH, condtion in whihc carilage continues to form new bones in adulthood, enlargement of hands, feet, face, jaw. most often caused by a tumor.
Pituitary dwarfism
Hyposecretion of hGH, extreme dwarfism. can be corrected if diagnosed in infancy.
Posterior Pituitary
extension of the nerve tissue of the hypothalamus.
Posterior Pituitary Hormones
first synthesized by the hypothalamus, then stored and secreted by the posterior pituitary.
How are posterior pituitary hormones controlled?
Initally stimulated by nerve impuses from the hypothalamus, maintained through positive feedback.
General Description of the Adrenal Glands
2. one superior to each kidney. divided into 2 structures, the arenal cortex and adrenal medulla.
Adrenal cortext
outer portion of the adrenal glands. protices steroid hormons derives from cholesterol.
Adrenal medulla
inner central portion of the adrenal glands.
Zona Glomerulosa
Outter most layer of the adrenal cortex, produces mineralocorticoids, main one being aldosterone.
Zona fasciculata
Middle layer of the adrenal cortexm produces glucocorticoids, main one being cortisol.
Zona reicularis
inner most layer of the adrenal cortex, produces gonadocorticoids, main hormones are, dehydroepiandrasterone(DHEA), androgens, estrogen and testosterone.
primarily regulate sodium homeostasis. Aldosterone is the main mineralocorticoids.
Functions of Aldosterone
controls the kidneys ability to regulate sodium, chlride, potassium and water. Increased levels of aldosterone causes kidneys to excrete potassium in urine and reasborb sodium and water.
help regulate lood glucose homeostasis. Cortisol is the main glucocorticoids. Refulated by negative feedback except during stress.
Function of Cortisol
Promotes gluconeogenesis with low glucose levels. Lipid metabolsim, excess cortisol leads to lipolysis. Meaintains normal blood pressure, excess cortisol increases, low lowers. Anti-immunity or anti-allergy effect. antiinflammatory effects. can be chronically elevated due to stress.
incude androgens and to a much lesser extent estrogen
Adrenal Insufficiency
also called addisons disease, adrenocortical hyperfunction, hypercortisolism. Occurs when underactive adrenal glands produce insufficent cortisol and occasionaly aldosterone.
Primary Adrenal Insufficiency
often due to autoimmune conditions. rarer cases include adrenal tumors, tuberculosis or other infections.
Secondary Adrenal Insuffiecy
due to decreased levels of adrenocorticiotropic hormone (ACTH) there is a drope in cortisol.
Symptoms of Adrenal Insufficency
Fatigue, constpiation, loss of appetite, diarrhea, craving salty food, weakness, muscle and joint pain, weight loss, darkening of the skin, nausea, vomiting, abdominal pain, diziness.
Treatment for Adrenal Insufficiency
Hydrocortisone, Prednisone.
Adrenocorticol hyperfunction
also called Cushing’s disease or hypercortisolism. often occurs when a person is exposed to chronically high levels of glucocorticoids. overproduction, highdoses of corticosteroids, tumors.
symptoms of adrenocortical hyperfunction
weight gain, thinning of skin, tiredness, weak muscles, increased acne, easy bruising, round face, high blood pressure, mood swings, increased thirst, poor wound healing, weak bones, high blood sugar, depression.
Treatment for adrenocorticol hyperfunction
high doses of treatment: dose adjustment
tumors: surgery radiation, medication
Symptons of Hyperaldosteronism
high blood pressure, excessive thirst, headaches, muscle weakness, excessive urination, cramps.
Treatment of hyperaldosteronism
surgical removal of tumor
What initiates the “fight or flight” response? How?
Adrenal Medulla.
Increases Blood pressure, increases heart rate, increases rate of respiration, decreases digestion rate,
hypersecretion of epinephrine, norepinephrine and dopamine. caused by a tumor on the adrenal medulla.
Symptoms of Pheochromocytoma
sudden tachycardia, extreme anxiety with a sense of impending death, cold perspiration, blurred vision, headache and chest pain, stroke, or heart failure.
Treatment of Pheochromocytoma
Prompt surgical removal of the tumor.
epinephrine, norepinephrine,dopamine.
General description of the Thyroid Gland
bi-lobed butterfly shaped gland located in the front and sides of the trachea below the larynx, connected by the isthmus.
What hormones are produced by the Thyroid Gland?
Thyroxine (T4)
Triiodothyronine (T3)
Functions of the Thyroid Hormones
T3 & T4 control the body’s metabolic rate.
Calcitonin regulates calcium homeostasis.
Thyroid Hormone Synthesis
1) ionized iodide is absorbed from the diet.
2) iodide trapped in the thyroid reacts with the tyrosines present on the surface of thyroglobin.
3) Iodination of tyrosine
4) coupling of T1 & T2
5) Digestion of Thyroid Hormones
6) Transport in blood.
How are thyroid hormones regulated?
Through Negative Feedback. hypothalamus secretes TRH stimulating the pituitary to secrete TSH, when thyroid levels rise, hypothalamus and pituitary stop producing TSH and TRH.
Physiologic Effects of the Thyroid Hormones on the body (T3 & T4)
Regulate the body’s BMR.
Increase Fat and carbohydrate metabolism
Stimulates Protein synthesis
Increase heart rate
Key role in growth and development of the brain in children
Enhance actions of th Catecholamines.
used to describe the signs and symptoms assoicated with the lack of sufficien thyroid hormones.
Sings and symptoms of hypothyroidism
fatigue, constipation, weight gain, coarse, dry hair, hair loss, weakness, muscle cramps and aches, irritability, dry, rough pale skin, abnormal menses, cold intolerance, depression, memory loss, decreased libido.
Primary Hypothyroidism
thyroid doesn’t produce enough T4. thyroid has failed, pituitary and hypothalamus functioning.
Hashimoto’s Thyroiditis
autoimmune disease, body attacks thyroid gland, often associated with goiter.
congenital defect in newborns that lack a properly functioning thyroid gland, low BMR, very slow growth and sexual development, mental retardation.
Hashimoto’s Thyroiditis
autoimmune disease, body attacks thyroid gland, often associated with goiter.
decreased metabolic rate which cases mental slowness, dry skin, hair loss, swollen skin, enlarged tongue, slowed speech, yellow skin, weight gain is common. older children or adults.
Iodine Deficiency
lack of iodine in the diet. causes decreased production of T3 and T4, causes goiter.
Other common causes of hypothyroidism
radiation, surgery, viral and bacterial infection.
Secondary hypothyroidism
pituitary gland does not release enough TSH. pituitary or hypothalamus have failed, thyroid is functioning. Often caused by tumors or destruction of the pituitary.
Treatment for hypothyroidism
thyroid hormone replacement therapy. LEvothyroxine synthetic T4
term used to describe the signs and symptoms associated with an over production of thyroid hormones.
Signs and symptoms of hyperthyroidism
palpitations, nervousness, light or absent menses, breathlessness, increased bowel, insomnia, fatigue, fast heart rate, trembling hands, weight loss, muscle weakness, warm moist skin, hair loss, staring gaze, heat intolerance.
Graves Disease
Most common type of hyperthyroidism. autoimmune disease, antibodies are directed against the TSH receptor sites. thyroid is stimulated to increase grwoth and function. symptoms include goiter, and exophtalmos.
Other causes of hyperthyroidism
overproduction of T3 and T4 from single or multiple nodules, excess secretion of TSH
Treatment for hyperthyroidism
anti-thyroid drug therapy, radioactive iodine, and/or surgical removal of all or part of the thyroid.
General Description of the Parathyroid Gland
4-5 parathryid glands are embedded in the thyroid gland. Primary hormone is Parathyroid Hormone (PTH) Not dependent on pituitary or hypothalamus.
Physiological effects of the bones of PTH
reduces the effect of new bone formation. Increases the amount of bone degradation which yields calcium and phosphate.
Physiological effects of the kidneys of PTH
causes calcium to be reabsorbed from urine and renter the blood. PTH causes phosphate to be removed from bone into the bloodstream. PTH inhibits the reabosrption of phosphate.
PTH effects in the intestines
PTH increases the body absorption of calcium from food. Vitamin D permits calcium ions to e transported into blood.
protein produced by the parafollicular cells of the thyroid. These cells are located next to the thyroid secreting cell hormones in the thyroid gland.
Physiological effects of calcitonin in the body.
Removes excess calcium from blood sends it to bones to increase bone formation. Inhibits bone breakdown. promtoes conservation of hard bone matrix.
Calcium homeostasis
acheived through combined action of PTH and calcitonin.
Low blood levels of calcium
stimulate secretion of PTH,
inhibits secretion of Calcitonin
High Blood Levels of Calcium
inhibit PTH
stimulate secretion of calcitonin
Physiological Importance of Calcium homeostasis
leads to normal:
blood clotting, strong teeth and bones, cell membrane permeability.
hyposecretion of PTH, causes low calcium levels, high phosphate levels. Treated with vitamin D and calcium supplements.
hypersecretion of PTH, high calcium, low phosphate, caused by tumors, treatment is removal of tumor.
surgical removal of all four parathyroid glands.
General description of the Testes
paired organs found within the scrotum. composed of coils of sperm-producing seminiferous tubules, between these are the interstitial cells of Leydig that produce testosterone.
responsible for growth and maitenance of male sexual characteristics, regualtes spermatogenesis, stimulates descent of the testis.
Inhibin (MEN)
secreted by the Sertoli Cells (sperm attaches to it until they are mature) inhibits secretion of the Follicle stimulating hormone. (FSH)
What hormone stimulates the testes to produce sperm?
Folicle Stimulating Hormone (FSH)
What hormone stimulates interstitial cells in the testes to develop and produce testosterone?
Leutinizing hormone (LH)
Increased Testosterone Levels
Can be caused by testicular, adrenal, or pituitary tumors. In young males could be precocious puberty.
Decreased Testosterone Levels
Hypogonadism, Klinefelter’s Syndrome, Orchiectomy, Delayed Puberty, Elderly Men, Alcohol use and Abuse.
What cells produce estrogen and progesterone?
Granulosa cells and thecal cells.
secreted by the follicle cells.
promotes the maturation of the ovum
stimulates growth of blood vessels in the endometrium
responsible for secondary sex characteristics in women.
Fundamental reproductive unit which consists of one oocyte(egg) surrounded by a cluster of granulosa cells.
Function of the Follicle
Maintain and nurture the oocyte and release it at the proper time. PRovide hormonal support for the fetus.
stimulated by LH, promotes storage of glycogen and further growth of blood vessels which become a placenta, influences the cells of the mammory glands.
Inhibin (WOMEN)
secreted by the corpus luteum, decreases the secretion of FSH and GnRH.
activity of the ovaries and the anterior pituitary gland and the resultant changes in the ovaries and uterus. involves FSH, LH, estrogen and progesterone.
Menstrual Phase of Mensus
loss of the functional layer of the endometrium, lasts 2-8 days, secretion of FSH increases.
Follicular Phase of Mensus
growht of follicles and secretion of estrogen is stimulated by FSH, functional layer regenerating, ends at OVulation.
Luteal Phase of Mensus
Under the influence of LH, the ruptured follicle becomes the corpus luteum, which secretes progesterone
conception. takes place in the fallopian tubes when a sperm enters an ovum.
developing human individual from the time of implantation to about 8 weeks of gestation.
developing human from 9 weeks to birth.
composed of both maternal and fetal tissue, serves as the site of nutrient exchange, oxygen and co2 exchange, secretes numerous hormones.
Umbilical Cord
conencts the fetus to the placenta
Placental Hormones
Human Chorionic Gonadotropin (hCG)
Placental Progesterone
Placental Estrogens
Humon Chorionic Somatommamotropin(hCS)
Human Chorionic Gonadotropin (hCG)
first hormone secreted by the blastocyst, detected in maternal plasma and urine about 3-9 days after conception.
Function of hCG
matins the corpus luteum, stimulates secretion of progesterone and estradiol, stimulates fetal adreanal glads, in male fetuses, stimulates the early secretion of testosterone which is critical to masculinize the genital tract.
Placental Progesterone
essential for successful implantation, inital sustenance and long term maitenance of the fetus, induces prolactin and mammory gland development, increases ventilation, quiets uterine muscle activity,
Placental Estrogens
Progessive increases in estradiol, estrone, estriol throught pregnancy, stimulates growth of uterine muscles, relax and softens the pelvic ligaments, augment growth of the duct system int he breasts.
Human Chorionic Somatomammotropin (hCS)
human placental lactogen, stimulates lipolysis and is an insulin antagonist,
stimulates lactogenesis of the breasts, and suppreses reproductive function of the mother.
relaxes the mother’s pelvis, softens the cervvix, decreases uterine muscle contraction.
10-15% of all conceptions, majority occurs within 14 days, later miscarriages refelct bad attatchement or abnormalities, Dx is made ith beta hCG assasy and ultrasound.
Ectopic Pregnancy
fertilized egg implants in the fallopian tube, leading cause of maternal mortality, Dx made with beta hCG assays, ultrasound, and laparascopy.
What are the laboratory tests to Dx Adrenal Cortex Disorders?
Plasma cortisol levels, Basal ACTH, Cortisol 24-hour Urine and ACTH stimulation test.
What are the laboratory tests to Dx Adrenal Medulla Disorders?
Plasma epinephrine, norepinephrine, and dopamine levels, urine 24 hour, metanephrine and vanillylmandelic Acid (VMA) levels.
When is the peak and trough for Plasma Cortisol?
peak : 0800-0900
Trough: 2300-0000
What is the most sensitive test for hypothyroidism, speciment requirements and reference range?
Thyroid Stimulating Hormone
Serum or plasma nonlipemic non hemolyzed
.4-8.9 mU/L
Total T4
measures Thyroxine in Serum.
Rules out hypo or hyper thyroidism, used to diagones any congenital defects in neonates.
Serum or heel stick (neonate screen)
Referance range Adult 5-12 ug/dL
neonate 32-216 ug/dL
Total T3
useful in hyperthyroidsim, limited value for hypothyroidism.
Serum is preferred
Adult 88-150 ng/dL
Neonate 32-216 ng/dL
FT3 – Free triiodothyronine
evaluates thyroid function, measures FREE t3 in blood. USed to rule out T3 thyrotoxicosis, evaulate thyroid replacement therapy and clarify protein-binding abnormalities.

.2-.52 ng/dL

TBG Thyroxine Binding Globulin
distinguishes between hyperthyroidism causing elevated T4 and euthyroid patients iwth increased T4 binding, hereditary deficiences of TBG
16-34 ug/mL
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