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Fundamentals I
September 23, 2008
Dr. Whikehart- Hormones
Slide 1: Hormones
 Hormones will be very important to the organ systems we will start studying in January and for
some of the material we will start in Fundamentals II.
 Hormones come from a Greek work that means “impetus” or stimulus, which is exactly what
hormones do.
 They amplify a signal.
Slide 2: Outline
 There are classifications and chemical types we will look at.
 Characteristics of the molecule and the molecular types
 We will learn a little bit about synthesis and destruction rates
 We will learn a universal method for assaying hormones that is used in almost every chemical
laboratory.
 Some general mechanisms
 Discussion about the endocrine system which is where hormones were 1st discovered and
investigated
 Miscellaneous Details Just what we were waiting for
 Summary of the hour’s lecture.
Slide 3: Hormones
 What are hormones?  Essentially messenger molecules that are meant to coordinate the
operations of biological organisms including people.
 The way this is accomplished is by increasing and decreasing the functions of cells and sometimes
just leaving the functions at their present level.
 They can do three things—increase function, decrease function, or leave it the way it is.
 Example of 2 related hormones that come from the thyroid gland called triiodothyronine and
thyroxine, which are abbreviated T3 and T4.
 What amino acid do these look like or are derived from?  Tyrosine. There is a little bit of
molecular mischief that goes on there to piggy back one tyrosine molecule on top of another to get
this very unusual looking hormone.
 The hormones are secreted by the thyroid gland and they have a very important function—they
increase metabolic rates throughout the body.
Slide 4: Diabetes and Dogs
 The first hormone to be discovered was called “anti-diabetic factor.”
 This was done in 1921 by three of the four individuals that are pictured on the slide—Banting, Best,
and Collip. It was done MacLeod’s lab in Toronto, Canada.
 Discovery of hormones, or just about anything in science, usually begins with some idea that
somebody has sometime before.
 The idea of diabetic factor came from Oscar Minkowski and Josef von Mering back in 1889 because
they produced diabetic dogs by removing their pancreases.
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What they really wanted to do was to study fat digestion so this came as a chance discovery. The
fact was that these two gentlemen were not able to isolate the hormone. The hormone isolation
did not take place until 1921.
Went through a securitious (I have no idea what word he said) route, that’s how science happens to
work.
Slide 5: Types of Hormones
 Classification of Hormones.
 Lots of different ways to do this--- molecular types or by location and function.
 We have external cell hormones--- classified into endocrine, paracrine, and autocrine hormones.
 The endocrine hormones are secreted by endocrine glands. We have endocrine glands and exocrine
glands.
 Endocrine glands are ones that secrete substances directly into the blood stream.
 Exocrine glands will secrete substances through a duct and often times those secretions will come
out to the surface of the body. Ex. A sweat gland.
 Endocrine glands will secrete hormones and other substances into the blood stream.
 What happen is that the hormones will travel through the blood stream until they come to some
target tissue—which really is a target cell like shown in the diagram on the slide.
 Paracrine hormones are local hormones which mean that they are pretty much isolated within a
given specific tissue. They make hormones that are made for cells within the given tissue. They are
usually secreted into the interstitial fluid rather than the blood stream.
 The third classification is called an autocrine gland. They are selfish hormones in the sense that they
are made by cell for the cell itself. It reinforces whatever it happens to do.
 Interestingly enough, some paracrine hormones also happen to autocrine hormones and vice versa.
 You can pretty much conclude that paracrine hormones and the autocrine hormones are a local
phenomena. They are not unimportant, however.
Slide 6: Types of Hormones 2
 What is on here is pretty much what I just said.
 Some examples—we had looked at some endocrine hormones before, but some examples of
paracrine hormones are cholecystokinin-8.
 There are actually about 3 or 4 hormones of this type—these are hormones made in the GI tract and
are meant to reinforce the function of the GI tract—they are simple peptides.
 Cholecystokinin-B consists of NH3-Asp-Tyr-Met-Gly-Trp-Met-Asp-Phe-CONH2, phenylalanine and
has an amide on the end so that carboxylic acid…. (this was an incomplete statement made by Dr.
Whikehart.
 Sometimes these hormones are slightly modified from a straight peptide and this one happens to be
in that sense.
 An example of an autocrine hormone is estradiol.
 Estradiol is also an endocrine as well--- will support cells of the womb during pregnancy.
Slide 7: Cyclic AMP
 Internal cell hormones are hormones that are made and function entirely within the confines of a
cell.
 They never appear outside the cell itself.
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They are often called 2nd messengers and are to be distinguished from some external hormones
such as steroids.
These types of external hormones will enter a cell from the outside to bind to some receptor inside
the cell—they are NOT internal cell hormones.
Example 3’-5’ cAMP or cyclic AMP. This is the 3rd manifestation of a nucleotide that we have seen so
far.
Some of them are used to make nucleic acids and some are used as energy cells or energy molecules
and now we have one that is hormone.
We have AMP, ATP, and cyclic AMP all of which have different functions.
Slide 8: Hormone Characteristics
 Size and Molecular weight.
 Typically, these are small molecules, but there are some exceptions.
 These are polypeptide hormones that really are proteins such as growth hormone.
 Example: oxytocin—a cyclic peptide because it is made cyclic by disulfide bond formation. You can
see that it has 8 amino acids to make the peptide. Its molecular weight is small—only slightly over
1000 and it is made in the posterior pituitary gland and stimulates uterine contraction at birth.
Slide 9: Duration of Existence
 Hormones generally have what are called short half lives.
 For example, if a hormones goes through the circulation one time, its half life may be reduced to
half the amount that it was originally secreted at.
 It might take 2 or 3 circulations through the blood stream before it loses half of its original
concentration.
 Generally these half lives are short and are measured in MINUTES.
 Some hormones have longer half lives than minutes, but most are minutes.
 In the bottom, the footnote in red you see that a half life is defined as the amount of time that a
substance exists until it is reduced by ½. The reduction of hormone (activity) often follows
exponential decay n(t) = no x 2-t/t1/2 after 3 half-lives only 1/8 of an active hormone survives.
 The reduction of hormone activity—there’s an important distinction—we can talk about the
hormone as it exists as a quantity and measurable weight like micrograms or nanograms or we can
talk about its ACTIVITY.
 Which of the two do you think is more important? ACTIVITY, because that is the concept that makes
the hormone function as it does.
 A lot of hormones are made in inactive form, or precursor form. When they are secreted into the
blood stream, they are made into an active from. Afterwards, they can be deactivated or they can
be absorbed but metabolically deactivated.
 For example, they could go to the liver where they go through some enzymatic activity that will
change. For example, a hydroxy group can be removed or taken off or something similar. That
hormone will be inactivated.
 Another way that a hormone can be inactivated is simply to take it up into the cell and put it into a
lysosome.
 A lysosome is a sub cellular organelle that has about 30 different destructive enzymes and a low pH
that will take care of the peptide or whatever happens to be in short order.
 So, there is a formula on the bottom on the page--- it tells you how to calculate half life.
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DON’T WORRY ABOUT THE FORMULA. Won’t ask us to calculate the half life but just in case you
really have a burning desire to know, you can see that you can apply the equation and after three
half lives, only 1/8 of an active hormone survives.
The concept of half life is somewhat deceiving---since there are other factors that will contribute to
hormone availability and this could also be interpreted as hormone activity to bring about a cellular
response.
Bioavailability—is the hormone free or is it bound? There are some hormones that are bound to
carriers and are not as active as free and unbound hormones.
Rate of synthesis---at the time that the hormone is doing its thing, is it being made at a maximum
rate or a minimal rate, or somewhere in between the two extremes?
This is important for the kind of response that will take place from the hormone.
The rate of degradation—what would the tissue contribute to the rate of degradation.
Slide 10: Synthesis
 The rate of degradation—what would the tissue contribute to the rate of degradation.
 The best thing overall that can be stated is that most hormones, once synthesized, only remain for
minutes before inactivation and/or removal by tissues like the liver, kidney, or lungs or even the
cells themselves that they bind too.
 The reason for all this is that the body must retain tight control over its functions—so synthesis and
release can take place very quickly in an active state.
 On the other hand, inactivation can take place quickly as well.
 Synthesis and release of hormones is just as important as activation.
 You need to think about that for an examination and for organ function when you get into organ
systems later one.
 Some hormones have counterparts that produce opposing effects.
 Insulin will promote the uptake of glucose into cells.
 Glucagon promotes glucose release from the liver.
 One increase the amount of glucose that is present in the blood, and the other one will reduce it
because it is causing cells that need the insulin to be nourished.
Slide 11: Graph of Hormones during Menstrual Cycle
 Example of varying levels of hormones during the menstrual cycle---this is to show you how varied
they can measurement.
 These are measurements made in blood---over a typical 28-day period, two hormones estradiol and
progesterone can vary by tremendous amounts.
 Not all hormones vary by this much—this is just to give you an extreme example.
Slide 12: How Fast Can Hormones Cause Effects?
 We are talking about insulin and insulin in relationship to normal functions and insulin in
relationship to diabetes as well a condition known as hypoglycemia.
 On this graph, we are looking at time in minutes which goes out to five hours.
 On the y-axis we are looking at blood glucose levels in milligrams/deciliter which means mg/100 ml
of blood.
 This is called a glucose tolerance test—meant to test for various functions, one of which is diabetes.
 The normal individual, which is indicated in light green, you can see that after this person drinks a
little bottle of glucose (this is how the test is administered) and then blood is drawn in certain time
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periods afterwards. The blood glucose level goes up to about 150-160 mg/dl and then starts to go
down. That’s the normal function because insulin is being secreted into the blood and the glucose is
being slowly taken up into the cells that are insulin dependent. This is what you would expect after
a normal meal.
In a diabetic, you see two factors. One is that the glucose levels are already high, indicating that the
amount of insulin that is being secreted into the blood is insufficient to handle a normal level, which
is somewhere around 80-100mg/100 ml.
You see that after one hour and two hours and three hours that the level of glucose remains high
due to the insufficient amount of insulin being secreted into the blood and not being taken up into
cells.
The third condition is hypoglycemia. This is one in which for varying reasons there is too much
insulin being secreted into the blood. Even after a test meal or after ingestion of a glucose liquid of
some type, there is hardly any change in the level of insulin itself.
This could come about for varying reason—one could be because of a tumor that could be present
in the pancreas. This could cause an excess amount of insulin secretion.
You can see that the hormone effects and this is an indirect measurement of insulin, can vary
depending on the condition that happens to be present in the body.
Slide 13: How are Hormones Assayed?
 The radioimmunoassay was developed back in the 1980.
 This is an advantageous assay rather than the normal clinical assays because it is able to measure
hormones in the level from 10-6 M to 10-15 M, which is very, very low.
 The reason why it is so sensitive is because you are combining radioactivity with an
immunoreactions.
 In the assay, what happen is that non radioactive hormone from the patient competes with a
standard amount of radioactive hormone for binding to an antibody.
 It would be intuitively obvious that the more of the patient’s hormone that is present, the less
radioactivity that will be measured in your final material that you are collecting.
 Looking at the diagram, you have a tube that you an antigen in. The antigen is a radioactive
hormone. Then you add to that a sample from the patient’s serum. The two of them are mixed
equally and then from that, you add an antibody that is specific for these two antigens.
 It will react equally with them because it is really reacting with the hormone substance itself.
 Again, you can understand that the more of the patient’s hormone is present, the more will be
bound to the antibody.
 Then you add a precipitating agent that will take all the antigen bound antibody material that is
present in here and spin it all down in a centrifuge and collect it at the bottom.
 You could run this assay in two ways.
 You could look at the amount of precipitate or you could look at the supernatant—both of these
methods work equally well.
 What do we have here? Here we have only the radioactive hormone.
 Here we have only the radioactive hormone and we are going to react it with antibody, but you vary
the amount of the hormone and construct a standard curve from that running through the whole
entire assay you did over here.
 There is no competition except to vary the amount of hormone you have. Then you construct a
standard curve that you see here.
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Now as it is, because of the nature of the binding, you do NOT want the curve to be a curve. If you
did, then what you would get would look like this
Out at one end of the reaction, the binding would be somewhat compromised.
What you are doing is plotting the logarithm, or the percentage of radioactive antigen bound verse
the log of the [] of the sample antigen to get a straight line. Like straightening out a competitive
enzyme reaction.
Then you run this test on the top and you look for the amount of radioactivity which is present, for
example, in your precipitate on the bottom.
Take and draw a line from that intersection on the curve and from that you get the logarithm
concentration of the sample. Take the antilog of that and you will have the amount.
It is not as complicated as it sounds – read through the notes on the page to get an idea of the
principles of this assay and how its run.
Chances he will ask about this assay are increased for exam 4. I didn’t say that – you didn’t hear
it, but it is probably a good likelihood.
Assay is not complicated, but you need to have an intuition about how it is run
Slide 14: Chemical Classes of Hormones
 Chemical classes of hormones and these are only examples. Realizes there are thousands of
hormones and if we really wanted to do this right we would have a separate course on hormones.
 Amino acid derived hormones – thyroxin. We have looked at this before and it is derived from
tyrosine and made in the thyroid gland.
 Peptide hormones – 2 examples are growth hormone and oxytocin, which are made in the posterior
pituitary gland.
 Growth hormone is NOT a peptide hormone as much as it is a protein because its molecular weight
is over 22,000 Daltons.
o What is the cut off for a polypeptide and protein mw? 10,000 mw.
Slide 15: Lipid Derived
 Cholesterol derived – many hormones derived from this.
o Cortisol and estradiol.
o Two black arrows show the differences between cortisol and estradiol.
 Making a little change in a hydroxyl group ( shown on the slide.) Removed the keto
group here and have only a hydroxyl here.
 Here we have added resonance in the “A” form what is from the original cholesterol
molecule.
 It doesn’t take much of a change to get much of a profound change of two
molecules.
o What else is different?
 The hydroxyl group is here (top image), and not here (bottom). Methyl group here
(top image) and not here (bottom.)
o Also have hormones derived from fatty acids. Usually arachadonic acid, one of the long
chain fatty acids and these hormones, in order to form, are usually cyclized.
o We see that here (image)
o Cortisol is anti inflammatory in nature and what it does and estradiol (29:17 – doesn’t make
sense) and supports uterine functions.
o Prostaglandin 2 alpha, example molecule here.
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There are many of these hormones, called eicosanoids. Due to fatty acid chain
length of the originator of the molecule, this causes contraction of smooth muscles.
Some eicosanoids are inflammatory or anti inflammatory in nature, depending on
whatever it needs to be.
These are short action, fatty acid derived ones, and are usually made locally.
Slide 16: General Hormone Mechanisms
 General hormone mechanisms – these are mechanisms that belong to the endocrine class of
hormones. I will be spending a little bit more time on these types.
 There are 2 basic mechanisms – one which occurs at the surface of the cell and the second at the
cell nucleus.
o Both require a receptor protein.
 One receptor protein is located at the cell surface. Here is the membrane receptor protein for the
first type (1). Hormone comes along and binds to the receptor and causes a number of functional
effects that will result in some physiologic difference in the cell by means of a 2nd messenger
hormone. These 2 are linked, the 2nd messenger hormones and the hormones that bind at the cell
surface. The 2nd messenger hormone could go to some location in the cell or it could go to the
nucleus itself and cause some effect.
 The second class of hormones takes place at the nucleus through a cell receptor protein. The
receptor protein you see here could be located in the cytoplasm and it some cases, in is in the
nucleus itself.
o When receptor protein binds to the hormone, it goes to an enhancer site. You know what
those are in DNA (we will talk more about those later tomorrow.)
Slide 17: The Endocrine Hormone System
 The word comes from the Greek word – (?) to separate inside.
 These hormones are released directly into the blood stream to be distinguished from the exocrine
glands (secrete product into a duct).
 These are made in a pecking order, a hierarchy. Something precedes something else in order for the
hormone to be produced, starting from the hypothalamus of the brain.
 There are some independent systems of the endocrine system that do not start in the brain.
o Example – pancreas (talk more about later.)
 The general objective of the operation of the hormones in the endocrine system is to coordinate
bodily functions so things don’t go haywire.
Slide 18: Major Endocrine Organs
 Here are the major endocrine organs and glands.
 I don’t except you to memorize all of them, but be familiar with some of them anyway.
 Everything begins in the hypothalamus and the pituitary gland and works its way down the various
portions of the body.
o Notable exception – the pancreas.
 For example, we have 2 hormones that are made. The hypothalamus will secrete a hormone and
the hormone then goes to the pituitary gland and will cause it to secrete a 2nd hormone that will go
to the thyroid (for example) and make T3 and T4.
Slide 19: The Endocrine “pecking order”
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Here is the endocrine pecking order.
It goes in the direction I have written the 4 arrows on.
We have the neuroendocrine origin of signals that could be something that signals to the brain
hunger or fear or a need for aggression.
Brain responds by sending signals to the hypothalamus which will release peptides (as indicated by
the 3 arrows here) or instead of secreting peptides that are hormones, it might send a neural signal
to the posterior pituitary. NOTICE THAT DIFFERENCE.
At the level of the hypothalamus, we have some hormones being made, but we also have neural
signasl being made that go to the posterior pituitary or hormones that go to the anterior pituitary.
o These are called the 1st targets – the tissues of the anterior and posterior pituitary.
What is an alternate name for pituitary? – Hypothesis.
There are many hormones from the anterior and posterior pituitary. What you see here is a list that
is incomplete, but the most important ones are listed here.
o Cortiocortropin – (ACTH) hormone has a mw of 4500.
o Thyrotropin – goes to the thyroid gland and has a mw of 28.000.
The hormones you see from the anterior pituitary, for the most part, are proteins.
Posterior pituitary – only 2 important hormones. Oxytocin and vasopressin. They are cyclic
peptides with a small mw.
o Vasopressin – antidiuretic hormone. Meant to cause retention of water- very important in
maintaining blood volume.
o Causes blood vessel constriction.
Then there is the pancreas. This is the independent hormone system; nothing “pecks” on it to make
it do anything. It only response to things like an increase in glucose in response to a feeding.
Adrenal medulla – controlled by CNS and we won’t spend much time on it.
So we have 1st targets. Hormones from the 1st hormone go to second targets like the adrenal cortex,
thyroid gland, ovaries and testes. Notice that some hormones bypass second targets.
o Growth hormone and somatotropin. Goes to bones, which grow through an enlargement or
lengthening of bones and to very other tissues to increase their metabolic rate.
Ultimate targets come from the 2nd targets. Example of that is thyroxin – has T3 and T4. (Actually
there are 4 hormones, but only 2 are important.)
o This goes to muscles, liver and many other tissues. Actually, it goes to almost all tissues of
the body. Muscles and liver are just examples of that.
o It causes a general increase in metabolic rate. Have someone with a high activity of the
thyroid gland – these people become hyperactive, their body temperature goes up. They
are overheated. There are gradations of this – don’t think that because someone likes the
room cooler than you do that they have a hyperactive thyroid.
Slide 20: Images illustrating hormonal secretion
 Here we go with the pecking order of these endocrine glands. We have various signals that are sent
to the brain – pain, fear (someone is about to hit you on the head), even body infections can cause
hormone reactions. Bleeding out, hemorrhaging, hunger – this is not an exhaustive list, just
examples.
 The brain responds to that by sending signals to the hypothalamus. All up to this point is neural, and
what takes place beyond the hypothalamus could be hormonal or neural.
 Hormones are sent by the portal blood vessel or portal blood system.
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Look at the arrow – hormones to go to the anterior pituitary where they will cause some action in
the anterior pituitary.
 The small hormones released from the hypothalamus used to be called “factors.” A factor is a catch
all turn – can be hormones, peptides or proteins. Meant at the time that the factors were being
investigated that something was taking place, but they didn’t know what molecular species was
involved in bringing it out.
 In the posterior pituitary, you see an effect that is neural in nature and what is going to be produced
from the posterior pituitary will be a hormone.
 Note the small hormones here going to the anterior pituitary.
Slide 21: Releasing factors
 Releasing factors, which are hormones, migrate to a primary target, the anterior pituitary, which
releases its own hormone. (For our example – hormone B.)
 B travels through the circulatory system to a secondary target tissue, causing the release of
hormone C. C then travels to its ultimate target tissue, binds to it, and brings about a physiological
effect in tissues and cells.
 Each stage of binding and release amplifies the original signal many fold over. The increase can be
of 106 from one of the hormone mechanisms known as cascades.
Slide 22: The Endocrine “pecking order”
 Here is the endocrine pecking order again – I am not going to go back over it.
Slide 23: We can follow a typical sequence of events to Signal an increase in metabolic rate
 We can follow a typical sequence of events to signal an increase in metabolic rate.
o Example a conflict presents in the CNS – the task has to be completed in a week. This causes
a little strain – an exam is coming up.
 The CNS signals this to the hypothalamus, causing the release of thyrotropin-releasing hormone
(TRH). This hormones travels to the anterior pituitary gland via the portal vein circulation, causing
the release of thyroid stimulating hormone (TSH).
 PLEASE KNOW THE DIFFERENCE BETWEEN TSH AND TRH.
 The TSH in turn is carried to the thyroid gland by the blood system, where it causes a release of
thyroxin and triodothyrine (T4 and T3).
 T4 and T3 bind to most cells in the nucleus and stimulate an increase in metabolic rate, causing you
to stay up late.
Slide 24: Some things not previously explained
 Here are some things not previously explained.
 Many hormones have feedback and shutdown mechanisms. For example, the thyroid hormone
causes TSH release by TRH to decrease. That is a feedback loop.
 There can be a lag before an effect can occur and its reverse. For example, growth hormones
effects are slow. They can take weeks, months to occur.
 Hormones excesses and diminutions can be pathological. For example, excess cortisol levels may
cause kidney stones. That is not a comfortable thing. I will spare you his gory details.
Slide 23: Not explained continued...
 There are other kinds of hormones, like cyclic nucleotides (I did indicate this to you) and there are
also ions and nitric oxide.
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Specific hormone actions are determined by the kind of receptors that they bind to.
o What does that mean? Suppose we have hormone A.
o Hormone A binds to 3 different cells, each of which has its own receptor. These receptor
proteins can be all different from one another.
o One hormone can then cause 3 different physiological responses.
o That is what I mean by specific hormone actions are determined by the kind of receptors
that they bind to.
Some hormones can function as hormones and neurotransmitters. It depends on their location.
o Examples – epinephrine and nor epinephrine. These can be hormones or
neurotransmitters, depending on where they are and what they are doing.
Slide 24: Summary
 Hormones are chemical messengers meant to coordinate the physiological survival and functions of
an organism.
 To say that they belong to a chemical class would be not true. They include peptides, polypeptides,
amino acid derivatives, proteins, steroids, fatty acid derivatives, cyclic nucleotide derivatives and
other types.
 It is a variety and they are meant to do specific kinds of jobs.
 Can NOT say that all hormones are proteins. That’s crazy.
Slide 25: Summary continued
 The concentrations of hormones are quite small. Remember what I told you – 106-1015, but these
small amounts of molecules will greatly amplify the effects that can be produced, and they are
assayed by RIA. KNOW THAT ASSAY.
 The endocrine system was the 1st to be studied. It continues to be studied. It originates, for the
most part, but not exclusively, in the hypothalamic and pituitary tissues from CNS signals.
 In the endocrine system, hormones bind either at a cell membrane receptor or at the nucleus by
means of a protein receptor.
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