Hormonal responses to exercise

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1. ALINA JAMIL
LECTURER
HAYAT INSTITUTE OF REHABILITATION
MEDICINE

2. NEUROENDOCRINOLOGY

Two major homeostatic systems involved in the
control and regulation of various functions.

systems involved are:

NERVOUS SYSTEM AND

ENDOCRINE SYSTEM,

working together to maintain homeostasis these
system are termed as neuroendocrine system or
response

3. 
Neuroendocrine system sense information, organize
response and deliver message to appropriate organ

Two systems differ in a way the message is delivered

Endocrine glands release chemical messenger
(hormones) into the blood while nervous system send
their information via neurotransmitter ( relay
messages from one nerve to another or from a nerve to
a tissue)

4. Hormone_ chemical substance that is secreted into
the body fluids by one or a group of cells & has a
physiological effect on other cells of the body.
local hormone ( histamine)
General hormone
Nature of hormone:

Hormones are divided in several classes based on
chemical makeup

Amino acid derivatives, peptides/proteins and steroids

Hormones are measured in microgram(10-
3
g),
Nanogram (10-
9
g) and Picogram (10-
12
g) gram

5. BLOOD HORMONE
CONCENTRATION

The effect of a hormone on a tissue is determined by the plasma conc.

Hormone concentration in plasma depends on:

1.Rate of secretion of hormone from gland

Magnitude of input

Stimulatory vs inhibitory input

2.Rate of excretion or metabolism of hormone

At receptor & by liver/kidney

3.Quantity of transport protein

Steroid hormones

4.Changes in the plasma volume

•
Effect of hormone exerts on a tissue is directly related to the number of
active receptors

7. BLOOD HORMONE CONCENTRATION
RATE OF SECRETION OF HORMONE

Endocrine glands release hormone directly into the blood to alter the
activity of tissues

The rate at which a hormone is secreted from gland is dependent on
the magnitude of the input & whether it is stimulatory or inhibitory in
nature.

The input in every case is chemical one.

Most endocrine glands are under the direct influence of more than one
type of input


The plasma hormone concentration shows the magnitude of the effect
at the tissue level


Concentration can be changed by altering the rate of secretion or
inactivation of hormone


Alteration can be by quantity of transport protein, and the plasma
volume

8. Metabolism and secretion of
hormones

Concentration of hormones in plasma is influenced by
rate at which it is metabolized ( inactivated ) and/or
excreted.


Inactivation takes place at over near receptors or in the
liver. “These are major sites of hormones metabolism”.


Kidneys can metabolize and excrete varieties of
hormones in their free forms

9. Rate of excretion of hormone:

Excretion of hormone in urine has been used as indicator
of its rate of secretion during exercise.

Blood flows to the kidney and liver during exercise
decreases

Rate of excretion and inactivation decreases, and this
results in an elevation of hormones at the plasma level.

Concentration of certain hormones is influenced by
the quantity of transport protein in the plasma

Steroid & thyroxine are transported bound to plasma
proteins

During exercise, plasma volume decrease due to movement
of water out of CVS thus increase in concentration of
hormones in the plasma.

10. Hormone receptor interaction:

Tissue responses to specific hormones, have specific
protein receptors which are capable of binding those
hormones.

Magnitude of effect depends on:

Conc of hormone

No. Of receptors on the cell

Affinity of the receptor for the hormone

Number of receptors varies from 500 to 1 lac/cell.

No. of receptors may be decrease when exposed to a
chronically elevated level of hormone and it is called
“down regulation”

This down regulation have diminished response for
the same hormone concentration.

11. Chronically exposure to low concentration of hormone
may lead to increase in receptors number called “up
regulation”,


By up regulation tissues become very responsive to the
available hormone.

When concentration of hormone is so high that all
receptors are bound to hormones is called
“saturation”

Use of drugs to block receptors eg: heart patient may
receive a drug that blocks receptor to which adrenaline
binds.

This prevents heart rate from getting too high during
exercise

12. MECHANISMS OF HORMONE ACTION

Mechanisms by which hormones modify cellular activity
includes:

Alteration of membrane transport mechanisms


Stimulation of DNA in the nucleus to initiate the
synthesis of a specific protein
Steroid hormones

Activation of a special proteins in the cells by second
messengers

cAMP

Ca++

Inositol triphosphate

diacylglycerol

Tyrosine kinase ( insulin & GH)

17. 
ENDOCRINE GLANDS, HORMONES
& FUNCTIONS

18. 
Major endocrine glands
are

Hypothalamus and
pituitary

Thyroid gland

Parathyroid gland

Adrenal gland

Pancreas

gonads

19. HYPOTHALAMUS AND PITUITARY

Pituitary gland is located
at the base of brain
attach to the
hypothalamus

It consist of two lobes
anterior pituitary
(adenohypophysis)
and posterior pituitary
(neurohypophysis)

20. ANTERIOR PITUITARY

Anterior pituitary secretes hormones under the action
of chemical signals by the hypothalamus or positive or
negative feedback system
Major hormones are:

Adrenocorticotropin (ACTH)

Growth hormone (GH)

Thyroid stimulating hormone (TSH)

Follicle-stimulating hormone (FSH)

Luteinizing hormone (LH)

Prolactin

21. ANTERIOR PITUITARY

Hypothalamus controls the activity of both the ant.
Pituitary and posterior Pituitary glands

GH released from ant. Pituitary gland & it is essential
for normal growth

GH increases during exercise to mobilize fatty acids
from adipose tissue and to aid in the maintenance of
blood glucose

23. GROWTH HORMONE 
GH is a anabolic hormone it stimulate tissue uptake of
amino acids, protein synthesis and long bone growth,
increase plasma glucose level, increase mobilization of
fatty acids from fatty tissue

24. GROWTH HORMONE

Stimulates release of IGFs

Essential growth of all tissues

A.A uptake & protein systhesis

Long bone growth



Reduces the use of plasma glucose

Increases gluconeogenesis

Mobilizes FAA from adipose tissue

26. POSTERIOR PITUITARY

Release two hormones

Anti diuretic hormone(vasopressin) Increase water
reabsorption from the kidney tubules , to maintain
blood volume

Oxytocin stimulator of smooth muscle , specially at
the time of labor.

During exercise , plasma volume decreases &
osmolality increases

27. 
Mechanism of ADH in controlling body fluids:

Low interstitial fluid causes osmo-receptors in
hypothalamus to shrinks, causing ADH to release.


Lower plasma vol results in atrial stretch reflex ,
stimulates hypothalamus to release ADH.

30. THYROID GLAND

Thyroid gland is stimulated by TSH
(primary stimulus)
to
synthesize two iodine –containing hormones

Trioiodothyroxine T3
(contains 3 iodine atoms)

Tetraiodothyrosxine (thyroxine) T4
(contains 4 iodine atoms)

They are free hormone concentration
(not bound to plasma
protein)

T3 and T4 are important in maintaining metabolic rate of
body, it also help other hormone to exert their full affect

31. THYROID GLAND

Low T3 characterized as lethargic and hypo kinetic.

Latent period for T3 is 6-12 hours ,& 2-3 days for T4

32. THYROID GLAND

During exercise the free hormone conc. Increases due to
changes in binding characteristic of the transport protein,
& the hormones are taken up at a faster rate by tissues.


Calcitonin:

Calcitonin also secreted by thyroid gland

It involves in the regulation of plasma
ca
++

Block release from bone

33. PARATHYROID GLAND

Prathyroid are four small gland located on the dorsal
aspect of thyroid gland

It is the primary hormone involved in the regulation of
plasma calcium levels,

The hormone increase plasma calcium level by
increasing its absorption from renal tubules, GIT and
it also stimulate bone to release calcium in the blood

It also regulate phosphate level in the blood

Exercise increases the concentration of parathyroid
hormone in the plasma

34. ADRENAL GLAND

Adrenal gland has two
component

Adrenal cortex

Adrenal medulla

35. ADRENAL MEDULLA


Situated directly on top of each kidney and stimulated by
the sympathetic nervous system

Secretes the catecholamines

Epinephrine: elicits a fight or flight response

Increase H.R. and B.P.

Increase respiration

Increase metabolic rate

Increase glycogenolysis

Vasodilation

Norepinephrine

Vasoconstriction increasing BP

37. ADRENAL CORTEX

The three different zones of adrenal cortex release
three different types of hormone

Mineralocorticoids

Aldosterone: maintains electrolyte balance specially Na
and K

Glucocorticoids

Cortisol :Stimulates gluconeogenisis

Mobilization of free fatty acids

Stimulates glucose synthesis

Blocks uptake of glucose into cells

(androgens, estrogens)

testosterone, estrogen, progesterone

40. PANCREASE

Located slightly behind the stomach , pancreases act
both as exocrine gland and endocrine gland

Exocrine portion release digestive juices

Endocrine portion release

Insulin

Gucagon (insulin antagonist)

Pancreatic somatostatin

41. INSULIN

Insulin is released from beta cells of islet of langerhans

Insulin stimulate tissue uptake of glucose and amino
acids, and gluconeogenesis

Insulin secretion is influenced by plasma glucose
concentration, amino acid concentration, sympathetic
and parasympathetic stimulation

Decreased concentration or improper functioning
insulin receptors results in raised levels of plasma
glucose called diabetes mellitus

42. TESTES & OVARIES

Testosterone and estrogen are the primary sex steroids
secreted by the testis and ovaries.

These hormones are not only important in
establishing and maintaining reproductive function.
they determine the secondary sex characteristics
associated with masculinity and femininity

Testosterone is secreted by the interstitial cells of the
testes and is controlled by interstitial cell stimulating
hormone (ICSH-also known as LH)

Sperm production from the seminiferous tubules of
the testes requires follicle-stimulating hormone (FSH)
from the anterior pituitary and testosterone.

44. Testosterone is both an anabolic (tissue building) and
androgenic (promoter of masculine characteristics)
steroid because it stimulates protein synthesis and is
responsible for the characteristic changes in boys at
adolescence that lead to the high muscle-mass to fat-
mass ratio

The plasma testosterone concentration is increased
10% to 37% during prolonged submaximal work ,
during exercise taken to maximum levels and during
endurance or strength training workouts

Some feel that these small changes are due to a
reduction in plasma volume or to a decrease in the rate
of inactivation and removal of testosterone

45. the testosterone response to exercise is small and the
concentration returns to resting values two hours after
exercise

there is evidence that the resting plasma concentration
is lower in both endurance-trained and resistance-
trained males

In one study, high mileage (108 km . wk- ' ) runners
had lower levels of testosterone, sperm count , and
sperm motility compared to moderate-mileage (54 km
‘.wk - ' ) runners

testosterone or one of its synthetic analogs as one of
the most abused drugs in the drive to increase muscle
mass and performance

46. Estrogen and Progesterone

Estrogen is a group of hormones that exerts similar
physiological effects

These hormones include estradiol, estrone, and
estriol

Estrogen stimulates breast development, female fat
deposition, and other secondary sex characteristics

49. 
the plasma levels of LH, FSH, estradiol, and
progesterone were measured at rest and at three
different work rates during both the follicular and
luteal phases of the menstrual cycle.

The patterns of response of these hormones during
graded exercise were very similar in the two phases of
the menstrual cycle

Figure 5.12 shows only small changes in progesterone
and estradiol with increasing intensities of work.

50. 
LH and FSH changed little or not at all during the luteal phase,
the small increases in progesterone and estradiol were believed
to be due to changes in plasma volume and to a decreased rate of
removal rather than an increased rate of secretion

the effect of the phase of the menstrual cycle on exercise
metabolism is not clear

evidence exists that estradiol decreases glycogen use and in
creases lipid use to result in an increase in performance

women who were matched for maximal aerobic power and
training with men had a lower rate of glycogen use during a
moderate intensity

women respond differently than men to training-induced
changes in exercise metabolism

there is general agreement that there are no menstrual cycle
phase effects on v02 max, and the lactate, plasma volume, heart
rate, and ventilation responses to exercise

51. 
concern is being raised about the effect of chronic
heavy exercise on the menstrual cycle of athletes

The two principal menstrual disorders are primary
amenorrhea (absence of menstrual cycles in a girl who
has not menstruated by 15 years of age) and secondary
amenorrhea (onset of amenorrhea sometime after
menarche)

exercise itself may not suppress reproductive function,
but rather the impact of the energy cost of the exercise
on energy availability.

52. HORMONAL CONTROL OF SUBSTRATE
MOBILIZATION DURING EXERCISE

The type of substrate and the rate at which it is utilized
during exercise depend to a large extent on the
intensity and duration of the exercise.

53. Muscle-Glycogen Utilization

At the onset of most types of exercise, and for the entire
duration of very strenuous exercise, muscle glycogen is the
primary carbohydrate fuel for muscular work

The intensity of exercise, determines the rate at which
muscle glycogen is used as a fuel

The heavier the exercise, the faster glycogen is broken
down.

This process of glycogen breakdown (glycogenolysis) is
initiated by second messengers, which activate protein
kinases in the muscle cell

Plasma epinephrine, a powerful stimulator of cyclic AMP
formation when bound to adrenergic receptors on a cell,
was believed to be primarily responsible for glycogenolysis

58. CONTROL OF MUSCLE GLYCOGEN
UTILIZATION

Breakdown of muscle glycogen in under dual
control

Epinephrine-cyclic AMP

via beta adrenergic receptors

Ca++- calmodulin


enhanced during exercise due to ca++ release from SR

Evidence for role of ca++ -calmodulin in glycogenolysis

_Propranalol (beta receptor blocker) has no effect on muscle glycogen
utilization

59. BLOOD GLUCOSE HOMEOSTASIS DURING
EXERCISE

Plasma glucose maintained through four processes:

Mobilization of glucose from liver glycogen stores

Mobilization of FFA from adipose tissues

Gluconeogenesis from AA, lactic acid, glycerol

Blocking the entry of glucose into cells


Controlled by hormones


Permissive & slow acting

Fast acting

60. 
Thyroid hormones:

Act in permissive manner to allow other hormones to
exert their effect by increase no. of receptors &
increase affinity of hormone for the receptor.


T3 enhances effect of epinephrine to mobilize FFA
from adipose tissue

No real change in T3 & T4 during exercise

61. 
CORTISOL:

Slow acting hormone

Effects:

Stimulate FFA mobilization from adipose tissue

Enhance gluconeogenesis in the liver

Decrease the rate of glucose utilization by cells

Effects of exercise:

Decrease during low intensity exercise 
increase during high intensity exercise/ long VO2 max

Changes in cortisol may be related to repair of exercise
induced tissue damage

64. GROWTH HORMONE

Slow acting hormone

Effects:

Supports the action of cortisol

_
decreases glucose uptake by tissues

_Increase FFA mobilization

_Enhances gluconeogenesis in the liver



Exercise effect:

Increase in plasma GH with increased intensity

Greater response in trained runners

67. Epinephrine/norepinephrine

Fast acting hormones

Maintain blood glucose during exercise

Muscle glycogen mobilization

Increasing liver glucose mobilization

Increase FFA mobilization

Interfere with glucose uptake

Plasma E & NE increase during exercise

Also related to related to increased heart rate & blood pressure
during exercise


Decreased plasma E & NE following training

71. Fast acting hormones

Insulin

_
uptake & storage of glucose

_ plasma conc. Decreases during exercise


Glucagon

_
mobilization of glucose & FFA fuels

_Plasma conc. Increases during exercise


Insulin & glucagon secretion influenced by
catecholamine’s