The study of hormones, their effects and the organs that produce them.
Endocrine System: Interacts with nervous system
Influences metabolic activity with hormones
Hormones: are chemical messengers
Lag time: seconds or even days
Response is more prolonged
Widespread and diverse effects
Widespread and Diverse Effects One hormone can affect more than one of
these at the same time. Several hormones
Reproduction may work together to affect one of these. We
Growth and development will learn these as we go.
Electrolyte, water and nutrient balance
Metabolism Our job here is to learn
which hormone does what.
Exocrine glands: 1. have ducts 2. produce nonhormonal substances 3. released in localized areas
Endocrine glands: 1. have no ducts 2. produce hormones 3. circulate all over the body
Autocrines – chemicals that exert effects on the same cells that secrete them
Paracrines – affects cell types other than those that secrete them (but these cells are very close)
Are these hormones part of the endocrine system?
Hormones chemical substances (chemical messengers)
Amino acid based – amino acids, peptides or proteins. Examples: _____________________
Steroids – made from cholesterol. Examples: ______________________________________
Eicosanoids – biologically active lipids. Examples __________________________________
Tumors: Some cancerous tumors of lungs, pancreas… synthesized hormones identical to those made by
glands but in uncontrolled and excessive amounts.
Assignment: for every chapter:
Mechanisms of Hormone Action about all the diseases!
How is it that hormones circulate throughout the body but effect only certain target cells?
What are target cells? ______________________________________________
The same hormone can cause different effects in different cells.
Hormones alter a target cells normal activity by increasing or decreasing it.
ex: Epinephrine causes smooth muscle to contract, but
causes sweat cells to increase production of sweat.
How is the target cell one time stimulated and another time inhibited? _______________
What if a cell does not have a receptor for that hormone? _________________________
Two Main Mechanisms Hormones Communicate to Target Cells
1. Amino acid based hormones involve the G proteins - 2nd messenger Mechanism
(a.) cAMP signaling mechanism
(b.)PIP-calcium signaling mechanism Be able to explain how each
2. Steroid Hormones: involve Direct Gene Activation of these systems work
1. Why such a complicated mechanism? Hormones that are proteins cannot pass through the cell
membrane. The signal is greatly amplified with each step, One molecule of TSH can cause the
thyroid gland to produce millions of molecules of thyroid hormone!
2. What stops the reaction caused by a hormone once it is started? Degradation of hormone, or
hormone slips out of the receptor and AMP is rapidly degraded within the cell
3. What keeps the reaction going longer, if that is needed? More of the hormone is released.
4. How is it that all cells are not affected by hormones that circulate throughout the body? The cell
has different receptors for different hormones
5. What if a cell does not have a receptor for that hormone? The cell will be unaffected by that
6. For “Direct gene activation” by steroid hormones, how is it that only this part of the DNA is
affected so that only this particular protein is synthesized? The receptors are located on this
specific segment of the DNA strand so that only this part of the DNA is activated.
All three are dynamic
Target Cell Activation Depends on: 1. Blood levels of hormone
and can change!
2. Relative numbers of target receptors
3. Affinity (strength) of bond between hormone and receptor
High affinity receptors hold tight to the hormone, once bonded, so that the hormone stays there for a
long time while the cell becomes more and more affected.
Low affinity receptors: hormone slips out of the receptors before the cell has been fully affected by the
Large numbers of high affinity receptors produce increased hormonal affects and smaller number of low
affinity receptors result in reduced target cell response
a. Up regulation - target cell forms more receptors
and/or exchanges low affinity for high affinity ones
b. Down regulation - target cell loses receptors and/or exchanges high affinity for low affinity ones
Why would cells do this up or down regulation? __________________________________________
Half Life, Onset and Duration of Hormone Activity
Concentration of hormone in the blood depends on:
1. Rate of release
2. Speed of deactivation and removal
a. Some are degraded quickly by enzymes within target cells
b. Most are removed by kidney or liver
Each hormone has its own half life,
Half-life – Length of time hormone remains in the blood onset and duration and must be
Onset – time required for hormone effects to appear very precisely controlled.
Duration – how long the effects last
Interaction of Hormones at Target Cells
Several different hormones may be acting on the same target cells at the same time: (3 ways)
Permissiveness one hormone is necessary for another hormone to be produced.
Example: TH effect on production of sex hormones
Synergism: More than one hormone produces the same effects on target cells and their
combined effect is greater than either one alone.
Example: Glucagon and epinephrine
Antagonism: hormones with opposite effects or one hormone inhibits the effect of another.
Example: glucagon and insulin.
Example: progesterone-estrogen interaction in the uterus.
Control of Hormone Release
1. Negative Feedback (2401) – Most hormones
Be able to explain what a negative feedback system is: Study the picture of insulin and
glucagon production in response to blood sugar levels and be able to explain how it all works.
2. Endocrine stimuli
a. Humoral – in response to changing levels of ions or nutrients in the blood
b. Neuronal – Neural fibers stimulate hormone release
c. Hormonal – Glands release hormone in response to hormone released by another endocrine gland.
Nervous System Modulation
Give an example of a hormone for each of these controls completely explaining each one.
All those things that stimulate or inhibit (humoral, hormonal or neural) can be modulated by the nervous
system.If they were not, the endocrine system would be no better than a thermostat - maintaining a set
value, taking nothing else into consideration. Explain this.
1. Body temperature: negative feedback systems keep body temperature at 37C. However, when we
are exercising or sleeping, temperature is modified so metabolism can keep pace with our activities
2. Blood glucose is maintained at 88-120, but in times of stress, the brain can over-ride by
stimulating a gland to release a hormone that increases blood sugar.
Pituitary gland (Hypophysis)
Anterior Pituitary (adenohypophysis) Summary
Posterior Pituitary (neurohypophysis) Produces 6 major hormones
and some minor ones
TSH – Thyroid Stimulating Hormone
(anterior pituitary) ACTH – Adrenocorticotropic Hormone
FSH – Follicle Stimulating Hormone
LH – Leutinizing Hormone
TSH GH – Growth Hormone
ACTH Tropic Hormones PRL – Prolactin
FSH POMC - Pro-opiomelanocortin
LH Can be split into:
PRL MSH – Melanin Stimulating Hormone
POMC ACTH Enkephalins and endorphins
Enkephalins and endorphins
POMC can be split into
MSH – Melanin stimulating hormone - a neurotransmitter in humans
Enkephalins and Endorphins which are natural opiates (pain killers)
GH stimulates cells to increase in size and divide (mostly bone and skeletal muscle cells
a. Promotes protein synthesis
b. Encourages use of fats for fuel (conserving glucose)
c. Raises blood glucose levels GH secretion is highest during sleep.
GH peaks during adolescence and
Growth hormone is mediated by IGFs * declines with age.
Growth hormone is regulated by GHRH and GHIH*
Insulin-like Growth Factors
IGFs (insulin-like growth factors) are produced by the liver, skeletal muscle and other tissues.
Production of IGFs is stimulated by GH.
1. Stimulate the uptake of amino acids from blood to make proteins
2. Stimulates uptake of sulfur for chondroitin sulfate for cartilage construction
3. Increases blood levels of fatty acids
4. Decreases rate of glucose uptake
5. Encourages glycogen à glucose in the liver to raise glucose levels in the blood
Homeostatic Imbalance of Growth Hormone – Read more!
Pituitary dwarfism __________________________________________________________
Gonadotropins are virtually absent from prepubertal children.
At puberty, these cells of the adenohypophysis activate and gonadotropin
levels rise and gonads are stimulated to mature.
What produces GnRH? _______________________________________
(PRL) High estrogen levels
PRL Stimulates milk production stimulates the release of ____
Low estrogen levels
PRH (Prolactin Releasing Hormone) Stimulates release of prolactin stimulates the release of ____
PIH (Prolactin Inhibiting Hormone) Inhibits the release of prolactin.
PIH dominates in males
Homeostatic Imbalance: of PRL
Hypersecretion of PRL (more common) _______________________________________________
Symptoms - __________________________________________________________________
Cause - ______________________________________________________________________
Hyposecretion of PRL _____________________________________________________________
Symptoms - __________________________________________________________________
Posterior Pituitary and Hypothalamic Hormones
1. ADH - Antidiruetic Hormone: influences water balance. How? Makes you retain water.
2. Oxytocin – stimulates smooth muscle contraction of uterus and breasts (ejection of milk)
Read other effects of oxytocin in both males and in females
ADH deficiency ________________________________________________________________
Cause – ____________________________________________________________________
Hypersecretion of ADH __________________________________________________________
Cause – ____________________________________________________________________
Differentiate between diabetes insipidus and diabetes mellitus. ______________________________
(Is really two hormones)
T4 – has four bound iodine atoms
T3 – has three bound iodine atoms
1. Increases metabolism and heat production of nearly all cells My
2. Maintains blood pressure. Baby Plays &
3. Proper skeletal proportions, Sings
4. Development of nervous system Nursery
5. Maturation of reproductive capabilities Rhymes
Homeostatic Imbalance (Thyroid hormones)
Hypothyroidism – ______________________________________________________
Hypethyroidism – ______________________________________________________
Goiter - ______________________________________________________________
Calcitonin is secreted by parafollicular cells in thyroid gland
Decreases calcium levels in blood (learned this in 2401)
Calcitonin Secreted by parafollicular cells in thyroid gland
Rising Ca2+ Thyroid gland Encourages deposition of
levels releases calcitonin Ca2+ in bone to decrease
Ca2+ levels in blood
Release Ca2+ from Parathyroid Falling blood
bone into blood releases PTH Ca2+ levels
The Parathyroid gland is located on posterior of thyroid gland
Chief cells – secretes PTH
PTH – elevates blood Calcium levels (be able to explain how it works)
1. Takes calcium out of bones
2. Kidneys activate vitamin D so intestine can absorb Calcium
3. Kidneys reabsorb Calcium
Homeostatic Imbalance (of Parathyroid hormone)
There are over a dozen corticoid hormones. All adrenal hormones help us cope with stress
1. Top of kidneys
2. Each are two glands
a. adrenal medulla (inner part)
b. adrenal cortex (outer part)
Mineralocorticoids (aldosterone) – secreted from zona glomerulosa
Glucocorticoids (cortisol) – secreted from zona fascicularis
Gonadocoricoids (androgen and progesterone) – secreted from zona reticularis
Maintains Na balance, thus maintains water balance by stimulating Na in the blood.
Increasing water will increase blood volume which increases BP
Cells: stimulates transcription of Na+/K+ pump Where Na goes, water follows.
Kidneys: reduces excretion and increases re-absorption of Na+ So aldosterone indirectly causes:
from kidney and increases output of K+ into urine 1. Water retention
Sweat: resbsorption of Na+ from sweat back into blood 2. Decreased urine output
Stomach: resorption of Na+ from gastric juice back into blood 3. Increased blood pressure
Other tissues: resorption of Na+ from saliva back into blood 4. pH changes
Homeostatic Imbalance of corticoids
Hypersecretion – aldosteronism __________________________________________________
Hyposecretion – Addison’s Disease _______________________________________________
1. Influence energy metabolism
2. Essential to life:
a. Keeps blood sugar constant
b. Maintains blood volume
Excessive amounts: ___________________________________________________
Stress, hemorrhage, Release of Increase glucose, fatty acids and amino
or infection glucocorticoids acids in blood stimulates fluid retention.
What are the consequences for long term stress? _______________________________
Androgens – converted to testosterone in males These hormones are secreted in
converted to estrogens in females very small quantities. Much more
are produced by the gonads. They
Homeostatic Imbalance of Gonadocorticoids only become important in older age
Hypersecretion – _________________________ when the gonads are no longer
Hyposecretion - __________________________ producing these hormones.
Hormones of the Adrenal Cortex
Mineralocorticoids: Aldosterone (Long acting hormones)
Aldosterone Glucocorticoids: Cortisol Gondadocorticoids: Sex Hormones
Catecholamines – epinephrine and norepinephrine* (Brief acting hormones)
Raises blood sugar
Vasoconstriction (elevates BP)
Increased heart rate and respiration rate
Stimulates sweat glands
Blood shunted to brain, heart and skeletal muscles Hyperglycemia
Increased metabolic rate
Homeostatic Imbalance of Rapid heart beat and
Deficiency – not a problem (read why) Intense Nervousness
Hypersecretion – uncontrolled sympathetic nervous system activity * Sweating
Cause: usually a tumor
Acinar cells – produce enzyme rich juice that is ducted to small intestine
Pancreatic islets (Islets of Langerhans)
α cells – produce glucagon *
β cells – produce insulin * Glucose uptake into cells
∆ cells – produce somatostatin β cells
release Excess glucose converted to
insulin glycogen in liver & skeletal muscles
Glucose is converted to fat
1. Glycogen à glucose Blood glucose
2. Release of glucose declines
3. Synthesis of glucose
from lactic acid … Imbalance of Pancreatic Hormones
Hypoglycemia – hyperinsulinism ___________________________________________________
Hyperglycemia (diabetes mellitus) __________________________________________________
Type I diabetes _______________________________________________________________
Type II diabetes_______________________________________________________________
Produce sex hormones
Ovaries – estrogens and progesterone
estrogens – 1. maturation of reproductive organs
2. Appearance of secondary sexual characteristics
estrogens + progesterone – breast development & menstrual cycle
3. Sex drive
4. Normal egg production
5. Maintains organs in mature functional state
Testes – testosterone:
1. maturation of reproductive organs Hypersecretion of
2. Appearance of secondary sexual characteristics testosterone over long
3. Sex drive periods of time ultimately
4. Normal sperm production results in feminization.
5. Maintains reproductive organs in mature functional state Explain this.
Melatonin – derived from seratonin
peak levels at night – makes us drowsy
lowest levels near “noon”
Exposure to bright light suppresses melatonin
Deep to sternum
Large in children – small and atrophied in adults
Thymopoietin Normal development of
Thymic factor T-Lymphocytes
Other Hormone Producing Structures
Heart ANP (atrial natiuretic peptide)
Gastrointestinal tract Gastrin, Serotonin, Intestinal gastrin, Secretin, Cholecystokinin
Placenta progesterone, hCG (human chorionic gonadotropin
Kidneys EPO (Erythropoietin)
Skin Cholecalciferol Will study these hormones in the
Adipose Leptin, Resistin chapters that cover these topics.