The Endocrine System
Chapter 11
Introduction
• The endocrine system is made up of the cells,
tissues and organs that secrete hormones into
body fluids.
• The body has two types of glands:
– Exocrine
• Secretes products into ducts
– Endocrine
• Secretes products into body fluids
General Characteristics of Endocrine System
• Endocrine glands and their hormones regulate
a number of metabolic processes within cells,
as well as reproduction, development and
growth.
• Endocrine glands include the pituitary gland,
thyroid gland, parathyroid glands, adrenal
glands, pancreas and other hormonesecreting glands and tissues.
Hormone Action
• A hormone is a biochemical secreted by one
cell that affects a specific target cell with
appropriate cell surface receptors.
• Prostaglandins are locally produced lipids that
affect the organ in which they are produced.
Control of Hormonal Secretions
• Hormone levels are very precisely regulated.
• Negative Feedback Systems
– Commonly control hormonal releases.
– When the concentration of the regulated
substance reaches a certain level (high or low), it
inhibits the gland from secreting more hormone
until the concentration returns to normal (if the
level is too high), or releases more (if the level is
too low).
Pituitary Gland
• Is attached to the base of the brain and has an
anterior lobe (anterior pituitary) and a
posterior lobe (posterior pituitary)
• The pituitary gland is controlled by the brain.
– Releasing hormones from the hypothalamus
control the secretions of the anterior pituitary.
– The posterior pituitary releases hormones into the
bloodstream in response to nerve impulses from
the hypothalamus.
Pituitary Gland
Anterior Pituitary Hormones
• Growth Hormone (GH)
– Stimulates body cells to grow and reproduce and
speeds the rate at which cells use carbohydrates and
fats
• Prolactin (PRL)
– Promotes milk production following the birth of an
infant.
• Thyroid-Stimulating Hormone (TSH)
– Controls the secretion of hormones from the thyroid
gland.
Posterior Pituitary Hormones
• Anti-Diuretic Hormone (ADH)
– Causes the kidneys to conserve water (prevents
dehydration)
• Oxytocin
– Plays a role in childbirth by contracting muscles in
the uterine wall and in milk-letdown by forcing
milk into ducts from the milk glands.
Thyroid Gland
• Located below the
larynx and consists
of two broad lobes
connected by an
isthmus.
Hormones of the Thyroid Gland
• Thyroid Hormones
– Increase the rate at which cells release energy
from carbohydrates, enhance protein synthesis,
and stimulate the breakdown and mobilization of
lipids.
– These hormones are essential for normal growth
and development.
– The hypothalamus and pituitary gland control
release of thyroid hormones.
Hormones of the Thyroid Gland
• Calcitonin
– Lowers blood levels of calcium and phosphate ions
when they are too high.
– Increases the rate at which calcium is stored in
bones and excreted in the urine.
Parathyroid Glands
• The four, tiny
parathyroid glands
are located on the
posterior of the
thyroid.
Hormones of the Parathyroid Gland
• Parathyroid Hormone (PTH)
– Increases blood calcium ion concentration and
decreases phosphate ion concentration.
– Stimulates bone breakdown by osteoclasts, which
releases calcium into the blood.
– Influences the kidneys to conserve calcium and
causes increased absorption of calcium in the
intestines.
– Calcitonin and PTH have opposite effects in
regulating calcium ion levels in the blood.
Adrenal Glands
• Sit atop the
kidneys enclosed
in a layer of fat.
Hormones of the Adrenal Gland
• Aldosterone
– Causes the kidneys to conserve sodium ions and thus,
water and to excrete potassium ions.
• Cortisol
– Influences the metabolism of glucose, protein and fat
in response to conditions that stress the body and
require a greater supply of energy in the bloodstream.
• Adrenal Sex Hormones
– Hormones that supplement those released by the
gonads and may stimulate early development of
reproductive organs.
Pancreas
• Secretes hormones
as an endocrine
gland and digestive
juices to the
digestive tract as
an exocrine gland.
Hormones of the Pancreas
• Glucagon
– Increases blood levels of glucose by stimulating the
breakdown of glycogen and the conversion of noncarbohydrates into glucose.
– Responds to low blood glucose levels
• Insulin
– Decreases blood levels of glucose by stimulating the
liver to form glycogen, increasing protein synthesis
and stimulating adipose cells to store fat.
– Responds to high blood glucose levels.
Pineal Gland
• Located near the
upper portion of the
thalamus of the
brain
Hormones of the Pineal Gland
• Melatonin
– Involved in the regulation of the circadian rhythms
of the body
• Circadian rhythms regulate our sleep/awake cycle.
Thymus Gland
• Located between
the lungs, under
the sternum
Hormones of the Thymus Gland
• Thymosins
– Affect production and differentiation of TLymphocytes that are important in immunity.
Reproductive Glands
• Ovaries
– Produce estrogen and progesterone in females
• Testes
– Produce testosterone in males
Disease Definitions
• Pathology: the science of causes and effects of
diseases
• Hyper-: more than normal
• Hypo-: less than normal
Adrenal Gland Disorders
• Addison’s Disease
– Pathology:
hypersecretion of all
adrenal cortex hormones
– Symptoms: Bronze skin
tone, muscles are weak,
burnout, susceptibility to
infection, hypoglycemia
Adrenal Gland Disorders
• Cushing’s Syndrome
– Pathology: tumor in
adrenal gland;
hypersecretion of
adrenal cortex
– Symptoms: extreme
obesity, hirsutism
(excessive hair growth),
“moon face”, “buffalo
hump”
Diseases of the Pituitary
• Giantism
– Pathology:
hypersecretion of GH
(growth hormone)
– Symptoms: overgrowth
of long bones leading to
excessive tallness
Diseases of the Pituitary
• Acromegaly
– Pathology:
hypersecretion of GH
– Symptoms:
Overdevelopment of
bones in face, hands,
and feet; cartilge is
attacked; chin protudes,
lips, nose, and
extremities enlarge
Disease of the Pituitary
• Dwarfism
– Pathology:
Hyposecretion of GH in
childhood (genetic)
– Symptoms: small size
(body proportions and
intellect are normal)
sexual immaturity
Diseases of Thyroid
• Hyperthyroidism
– Pathology:
hypersecretion of
thyroxine
– Symptoms: consumption
of large quantities of
food but loss of body fat
and weight; enlargement
of the gland (GOITER)
and bulging of the
eyeballs
(EXOPTHALMOS)
Diseases of the Thyroid
• Hypothyroidism
– Pathology: hyposecretion of thyroxine in
adulthood
– Symptoms: dry and itchy skin, dry and brittle hair,
muscle cramps at night
• Cretinism
– Pathology: hyposecretion of thyroxine in
childhood
– Symptoms: dwarfism during childhood
Diseases of the Parathyroid Gland
• Tetany
– Pathology: hyposecretion of parathyroid hormone
– Symptoms: development of convulsive twitching
Sex Related Endocrine Diseases
• Central Hypogonadism
– Pathology: hyposecretion of FH and LH from the
pituitary gland
– Females: (BEFORE PUBERTY) no menstruation or
breast development; (AFTER PUBERTY) hot
flashes, loss of body hair
– Males: breast enlargement, decreased beard and
body hair, muscle loss
Diseases of Pancreas
• Diabetes Mellitus
– Type 1 (“Juvenile Diabetes”)
• Pathology: body’s immune system attacks and
destroys cells in Islets of Langerhans
• Effect: Pancreas unable to secrete enough
insulin
• Treatment: Insulin shots
Diseases of Pancreas
• Diabetes Mellitus
– Type 2
• Pathology: muscle, fat, and liver cells become unable to
respone to insulin properly (as a result of poor diet, low
activity level, excess body weight around the waist)
• Effect: Cells unable to use blood sugar for cellular
respiration
• Treatment: strict diet and exercise; doctor may prescribe
medication that lowers blood sugar
• Long term effects: blindness, infection needing
amputation, nerve damage, damage to blood vessels and
nerves
Disease of Pineal Gland
• SADS (Seasonal Affective Disorder)
– Pathology: hypersecretion of melatonin
– Symptoms: cells prepare for winter, sleepy, sad,
tired, gain weight, depression
Diseases of the Thymus Gland
• Relatively rare and potentially serious
• Mainly Genetic
• Severe Combined Immunodeficiency disorder
(SCID)
– Pathology: mutation in a gene that affects the
development of T cells and other immune cells
– Symptoms: compromised immune system;
inability to fight off infections