Endocrine Glands
Endocrine Glands
• Hypothalamus
• Pituitary
– Anterior lobe
– Posterior
lobe
• Thyroid gland
• Parathyroid
glands
• Adrenal
Glands
– Cortex
– Medulla
Hormonal Communication
• Islets of
Langerhans
• Gonads
– Ovaries
– Testes
• Pineal gland
• Thymus
• others
Hypothalamus
• Part of brain
– Regulates ANS,
emotions,
feeding/satiety,
thirst, body
temperature, etc.
– Hormones related to
these functions
• “Releasing hormones”
• Axonal transport to
posterior lobe
Anterior Pituitary
• “Releasing” hormones
regulate AP aka
adeno hypo physis
“glands” “under” “growth”
• All proteins
– TSH (thryoid stimulating
hormone/thyrotropin)
– ACTH (adrenocorticotropic hormone)
– FSH (gonadotropin)
– LH (gonadotropin)
• Tropins/tropic hormones
– GH (growth hormone)
– Prolactin-releasing H
Hypothalamic Pituitary Axis Animation : IP Web
Anterior Pituitary
Anterior P. Homeostatic Imbalances
Growth hormone (GH or hGH)
– Promotes mitosis, cell division
– Elongation of long bones, etc.
– Healing of wounds Lack of hGH
retards growth
– Hypersecretion in youth produces
giantism
– Hyposecretion in childhood
produces pituitary dwarfism
– Hypersecretion in adult produces
acromegaly
Posterior Pituitary
• Axonal transport to
Posterior Pituitary aka
neuro hypo physis
“nerve” “under” “growth”
• Hypothalamic cell
bodies synthesize
– oxytocin
– ADH
Pituitary—Posterior lobe
• Oxytocin
– Stimulates smooth
muscle contraction
of uterus &
mammary glands.
• Antidiuretic H.
– Stimulates water
reabsorption in
collecting ducts.
– Stimulates
vasoconstriction
(vasopressin)
– Lack  diabetes
insipidus
Posterior Pituitary Homeostatic
Imbalances
ADH
– Hyposecretion produces
diabetes insipidus “tasteless”
– Excessive thirst and urination
• central or neurogenic DI
• gestagenic or gestational DI
• nephrogenic DI
• dipsogenic DI
Diabetes Insipidus Foundation, Inc.
Thyroid Gland
• Location in neck
– Inferior to larynx
– Anterior & lateral to
trachea
• Composed of follicles
– Follicle cells produce
thyroglobulin
• Thyroxin (T4)
• Triiodothyronine (T3)
– Both “thyroid hormone”,
body’s major metabolic
hormone
• Parafollicular/ C cells
• Calcitonin
– Decreases blood Ca2+ by
depositing it in bones
Homeostatic imbalances
• Hypothyroidism results
– Myxedema (in adults)
– Goiter—low levels of iodine
– Cretinism (in children)
• Hyperthyroidism results
– Graves disease
Parathyroid Glands
• Four small glands
embedded in posterior
of thyroid
– Parathyroid hormone
(PTH)
– Stimulates osteoclasts
to free Ca2+ from bone
– Stimulates Ca2+ uptake
from intestine & kindey
Hormonal Regulation of Calcium
Parathyroid Homeostatic
Imbalances
• Severe
hyperparathyroidism
causes massive bone
destruction
• If blood Ca2+ fall too
low, neurons become
overactive, resulting in
tetany
Feedback Loop
•
Negative feedback in calcium
homeostasis. A rise in blood
Ca2+ causes release of
calcitonin from the thyroid
gland, promoting Ca2+
deposition in bone and
reducing reabsorption in
kidneys.
•
A drop in blood Ca2+ causes
the parathyroid gland to
produce parathyroid hormone
(PTH), stimulating the
release of Ca2+ from bone.
•
PTH also promotes
reabsorption of Ca2+ in
kidneys and uptake of Ca2+ in
intestines.
Adrenal Glands
One on top of each
kidney
• Cortex
– Corticosteroid
– glandular
• Medulla
– Catecholamines
– neurohormonal
• Epinephrine
• Norepinephrine
Adrenal Cortex
• Cortex
– Activity stimulated by ACTH
– Controls prolonged responses
by secreting corticosteroids.
– Mineralcorticoids
• Aldosterone
balance
regulate salt and water
– Glucocorticoids
• Cortisol regulate glucose metabolism
and the immune system.
– Gonadocorticoids
• Androgens
• Estrogens
Adrenal Cortex Imbalances
• Hypersecretion leads
to Cushing’s disease
– ACTH-releasing tumors
or side effects of
corticoid drugs.
• Hyposecretion leads
to Addison’s Disease
– Deficits in
glucocorticoids and
mineralcorticoids
Adrenal Medulla
• Medulla
– The adrenal medulla mediates
short–term responses by secreting
catecholamine hormones.
– Cells are modified neurons (lack
axons)
• Epinephrine (adrenaline)
• Norepinephrine (noreadrenaline)
– enable a rapid ( fight-or-flight )
responses to stress by increasing
blood glucose and blood pressure
and directing blood to the heart,
brain, and skeletal muscles.
Pancreas
• Consists of two major
types of secretory tissues
which reflects its dual
function
– Exocrine gland
• secretes digestive juice
• localized in the acinar cells
– Endocrine gland
• releases hormones
• localized in the islet cells
(islets of Langerhans)
Pancreatic Islets
• “About a million”
embedded in pancreas
• Control centers for blood
glucose
– Insulin from beta cells
– Glucagon from alpha cells
Insulin
Glucagon
Islets of Langerhans
• Insulin stimulates
glucose uptake,
glycogenesis
• Glucagon
stimulates
glycogenolysis,
glucose release
from liver (vs
gluconeogenesis)
Feedback Loop
•A rise in blood glucose
causes release of insulin
from beta cells the
pancreas, promoting
glucose uptake in cells
and storage as glycogen
in the liver.
•A fall in blood glucose
stimulates alpha cells in
the pancreas to secrete
glucagon, which causes
the liver to break down
glycogen and release
glucose.
Pancreas Homeostatic Imbalances
Diabetes “siphon” mellitus mel= “honey”
Symptoms:
•Polyuria
•Polydipsia
•Polyphagia
Blood Level Regulation in Diabetics
Gonads
• Ovaries
– Estrogens
– Progesterone
• Testes
– Testosterone
• Reproductive functions
when we study
reproductive system.
Pineal gland
• Melatonin
– ? Inhibits early puberty
– ? Day/night cycles
• Timing of sleep, body
temperature, appetite
• Secretes melatonin during
darkness
– Participates in setting the
body’s clock
• Melatonin is a potent
antioxidant
• Melatonin is high when young
and is reduced as we age
Thymus
• Thymus gland
• Thymopoietins,
thymic factor,
thymosins
– Influence development
of T lymphocytes
Non-Endocrine Gland Hormones
• Stomach (gastrin)
• Small intestine (duodenumintesetinal
gastrin, secretin, cholecystokinin)
• Heart (atrial natriuretic peptide)
• Kidneys (erythropoietin, active vitamin D3)
• Adipose tissue (leptid, resistin)
• Skin
• Placenta (human chorionic gonadotropin,
human placental lactogen, relaxin)
Functions regulated by the
Endocrine System
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Growth
Healing
Water balance & Blood Pressure
Calcium Metabolism
Energy Metabolism
Stress
Regulation of other Endocrine
Organs
Growth
• Growth hormone-releasing
hormone
• Human growth hormone (hGH)
• Thyrotropin (TSH)
• Thyroxine & triiodothyronine
• Calcitonin
• Somatostatin (GHIH)
Healing
• Growth hormone-releasing
hormone
• Human growth hormone (hGH)
• Thyrotropin (TSH)
• Thyroxine & triiodothyronine
• Calcitonin
• Glucagon, Insulin
• Erythropoietin
Water balance & Blood
pressure
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ADH
Aldosterone
Angiotensin II
Atrial natriuretic H.
Epinephrine
Calcium Metabolism
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Calcitonin
Parathyroid H. (PTH)
Estrogens/androgens
Growth hormone
Energy Metabolism
• Thyroxine & triiodothyronine
• Thyroid-stimulating H. (thyrotropin,
TSH)
• Epinephrine & norepinephrine
• Insulin
• Glucagon
• Adrenocorticotropic H. (ACTH)
• Cortisol
Stress
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Epinephrine & norepinephrine
T4 &T3 ??
ACTH
Cortisol