Dr.Md.
Abdur Rahman (Bijoy)
Thyroid
gland
Endocrine
gland
The cells, tissues, and organs are called
endocrine glands-
• They are ductless
Hormone secretion
• They use the bloodstream
Endocrine
cell • They secrete hormones
• There are also similar glands called
paracrine and autocrine glands that are
quasi-endocrine.
Blood flow
(a) Skin
Glands that secrete substances are
Duct the exocrine glands-
• They have ducts
• They deliver their products directly to
Exocrine gland
(sweat gland)
a specific site.
Exocrine
cells
(b)
Nerve impulse
Neuron
Neurotransmitter Post-
transmits
released into synaptic
nerve
synapse cell responds
impulse
Target cells
(cells with hormone
Glandular receptors) respond
cells secrete to hormone
Bloodstream
hormone into
bloodstream
Hormones have no
effect on other cells
Hypothalamus
Pituitary gland Pineal gland
Chemically, hormones are either:
Parathyroid gland
• Lipid-soluble Hormones
Thyroid gland
Steroid hormones
Thyroid hormones
Thymus
Nitric oxide (NO)
Kidney
Adrenal gland
Pancreas
• Water-soluble Hormones
Amine hormones
Peptide hormones and protein
Ovary
(in female)
hormones
Testis
Eicosanoid hormones
(in male)
1. Hormonal mechanism: for example, the hypothalamus secretes
hormones that stimulate the anterior pituitary gland to secrete
hormones that stimulate other endocrine glands to secrete
hormones.
2. Humoral mechanism: for example, capillary blood contains a low
concentration of calcium that stimulates secretion of parathyroid
hormone. Parathyroid hormone makes serum calcium go up.
3. Neural mechanism: preganglionic SNS fiber stimulates the
adrenal medulla cells to secrete catecholamines.
– Hypothalamus – Nervous system – Changing level
of substance
in plasma
– Anterior pituitary gland
Peripheral Endocrine Endocrine
endocrine gland gland
gland
Target cells Target cells Target cells
Action Action Action
ORTICOTROPIN-RELEASING HORMONE
ROWTH HORMONE-RELEASING HORMONE
ONADOTROPIN-RELEASING HORMONE
ROWTH HORMONE- INHIBITORY HORMONE
HYROTROPIN-RELEASING HORMONE
ROLACTIN - INHIBITING HORMONE
ELANOCYTE - STIMULATING HORMONE
Third ventricle
Hypothalamus
Anterior cerebral
artery Optic chiasma
Optic nerve Oculomotor
nerve
Pituitary stalk Trochlear nerve
(Infundibulum)
Anterior lobe Posterior lobe
of pituitary gland of pituitary
gland
Sella turcica
Sphenoidal
sinus
Sphenoid bone Basilar artery
ROWTH / SOMATOTROPIC HORMONE
HYROID-STIMULATING HORMONE
ROLACTIN / LACTOGENIC HORMONE
DRENOCORTICOTROPIC HORMONE
UTEINIZING HORMONE
OLLICLE-STIMULATING HORMONE
ELANOCYTE-STIMULATING HORMONE
• Growth hormone (GH): controls growth and protein,
carbohydrate, and lipid metabolism. Production of growth
hormone is controlled by two other hormones:
1. Somatostatin: inhibits growth hormone.
2. Somatotropin: stimulates secretion of growth hormone.
• The majority of growth hormone is secreted during sleep. Other
factors that increase secretion of growth hormone are exercise,
stress, hypoglycemia, starvation, and hypothyroidism.
1. Prolactin: stimulates breast growth and production of milk.
2. FSH: stimulates development of egg and sperm and secretion
of sex hormones.
3. LH: stimulates the production of progesterone and regulates
ovulation in women, and regulates testicular growth,
testosterone production, and androgen production in men.
To stimulate the release of these gonadotropic
hormones, gonadotropin-releasing hormone (GnRH)
must be present.
Important for cervical dilatation prior to birth, and helps the uterus to
contract during labor and delivery, especially during the second and
third stages. In breast-feeding (lactating) mothers, oxytocin causes
milk to be “let down” into area of breast where baby can suckle and
receive milk.
When ADH is secreted, WATER is retained in the vascular space.
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Larynx
Colloid
Thyroid
Follicular
gland
cell
Follicular cells
Colloid Isthmus
Extrafollicular
cell
(a)
(b)
Extrafollicular
cells
© Fred Hossler/Visuals Unlimited
When thinking about thyroid hormones think energy
and metabolism!
1. Increases the metabolism of protein, fat, and glucose.
2. Increases body temperature in response to an elevated
metabolism, which produces body heat.
3. Increases the use of oxygen as metabolism increases.
4. Aids in the development of the neural and skeletal systems in
fetuses.
5. Helps regulate secretion of growth hormone.
6. Aids in production of red blood cells.
7. Affects respiratory rate: too much thyroid hormone increases
respiratory rate, and too little decreases respiratory rate.
8. Aids in normal growth and development.
• Both T3 and T4 increase metabolic rate of cells and tissues.
• T4 is the precursor to T3.
• T3 regulates the metabolic rate of all cells and all processes of cell
growth and tissue differentiation.
• T3 and T4 indirectly increase blood glucose levels.
• Being cold increases the conversion of T4 to T3.
• Things such as stress, starvation, certain dyes, and certain drugs
like steroids, beta-blockers, PTU (propylthiouracil), and
amiodarone decrease the conversion of T4 to T3.
• Targets the bones, kidneys, and epithelial cells of the intestines.
• Decreases blood/serum calcium in three ways:
1. Decreases intestines’ ability to absorb calcium.
2. Decreases osteoclast activity in the bones.
3. Decreases calcium resorption from the kidney tubules.
Bone resorption occurs when osteoclasts break down
bone and release calcium from the bone into the
blood.
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Secretory cells Pharynx
Thyroid
gland
Capillaries Parathyroid
glands
© R. Calentine/Visuals Unlimited
Esophagus
Trachea
Posterior view
Foods
Cholesterol
• Parathyroid hormone (PTH) makes
the serum calcium level go up!
Intestinal enzymes
Provitamin D • Too much PTH
Ultraviolet light in skin
hyperparathyroidism
Vitamin D hypercalcemia,
hypophosphatemia, bone damage,
(Cholecalciferol)
Also obtained directly
from foods
and renal damage.
Liver
Hydroxycholecalciferol • Too little PTH hypoparathyroidism,
Kidney Stimulated by PTH
hypocalcemia,
Dihydroxycholecalciferol hyperphosphatemia, hyperreflexia,
(active form of vitamin D)
Controls absorption of and cognitive changes (altered
Ca+2
calcium in intestine
sensorium).
Ca+2
Ca+2
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Parathyroid glands (on
posterior of thyroid gland)
Release into
bloodstream
Decreased blood calcium Increased blood
Stimulation stimulates parathyroid – calcium inhibits
hormone secretion PTH secretion
Inhibition
PTH
Bloodstream
PTH PTH
Ca+2 Ca+2 Ca+2
+ +
Bone Kidneys Intestine
releases Ca+2 conserve Ca+2 and absorbs Ca+2
activate Vitamin D
Active
Vitamin D
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Capsule Surface of
adrenal gland
Zona Connective
glomerulosa Adrenal gland tissue capsule
Zona
Kidney
lomerulosa
Zona
fasciculata
Cortex
Zona
Adrenal fasciculata
Adrenal cortex cortex
Adrenal
medulla
Zona
reticularis
Zona
reticularis (a)
Adrenal
Medulla
medulla
(b)
Chromaffin
cells
© Ed Reschke
Many heart attacks occur during the early morning hours when
people are coming out of REM sleep, as this is a very stressful
time for the body.
1. Stimulate gluconeogenesis (the formation of carbohydrates from
proteins and other substances by the liver).
2. Provide amino acids and glucose during times of stress.
3. Suppress the immune system due to powerful immunosuppressive
and anti-inflammatory properties.
4. Stimulate fat breakdown.
An increase in aldosterone secretion is also caused by:
• Low fluid volume levels in the vascular space as in shock or
hypovolemia.
• High blood levels of potassium.
The illnesses associated with aldosterone are:
• Hyperaldosteronism (Conn’s syndrome)
• Hypoaldosteronism
Sex hormones are usually broken down into three categories:
1. Androgens, testosterone being the main one.
2. Estrogens, estradiol being the main one.
3. Progestagens, progesterone being the main one.
Synthetic androgens (sex hormones) are referred to
as anabolic steroids.
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Pancreatic islet (Islet of Langerhans) Gallbladder Common bile duct
Pancreatic duct
Duct Pancreas
Small
intestine
Digestive enzyme-
secreting cells
Pancreatic islet
(Islet of Langerhans)
Capillary
Hormone-secreting
islet cells
From Kent M. Van De Graaff and Stuart Ira Fox, Concepts of Human Anatomy and
Physiology, 2nd ed. ©1989 W m. C. Brown Publishers, Dubuque, Iowa. All Rights
Reserved. Reprinted with permission
Pineal Gland
• Secretes melatonin
• Regulates circadian rhythms
Thymus Gland
• Secretes thymosins
• Promotes development of certain lymphocytes
• Important in role of immunity
Reproductive Organs
• Ovaries produce estrogens and progesterone
• Testes produce testosterone
• Placenta produces estrogens, progesterone, and
gonadotropin
Other organs: digestive glands, heart, and kidney
Stress results from changes
Hormonal signals
in the external environment
Neural signals
Signals from
sensory receptors
Sympathetic impulses
Hypothalamus
CRH released
Adrenal medulla Anterior pituitary
Epinephrine and Norepinephrine ACTH released
norepinephrine released
released
Adrenal cortex
Short-term “fight or flight” or alarm stage.
Cortisol released
• Blood glucose increases.
• Blood glycerol and fatty acids increase. Long-term adjustment or resistance stage
• Heart rate increases.
• Blood pressure rises. • Increase in blood concentration of amino acids.
• Breathing rate increases. • Increased release of fatty acids.
• Air passages dilate. • Increased glucose formed from
• Pupils dilate. noncarbohydrates—amino acids (from
• Blood flow redistributes. proteins) and glycerol (from fats).
test Normalvalues significance
Thyroid-stimulating 0.5–5.0 U/mL ↑ in primary hypothyroidism
hormone ↓in primary hyperthyroidism
Triiodothyronine (T3) 80–200 ng/100 mL ↓ in hypothyroidism
↑ in hyperthyroidism
Thyroxine (T4 ) 4–12 g/100 mL ↓ in hypothyroidism
↑ in hyperthyroidism
test Normalvalues significance
Parathyroid 25 pg/mL ↑ in primary hyperparathyroidism
hormone ↓ in primary hypoparathyroidism,
parathyroid trauma during thyroid
surgery
Calcium 8.5–10.5 mg/100 mL ↑ in some cancers,
hyperparathyroidism
↓ in hypothyroidism
Phosphorus 2.4–4.7 mg/dL ↑ in hypoparathyroidism
↓ in hyperparathyroidism
test Normal values significance
Growth hormone 5 ng/mL ↑ in acromegaly
↓ in small stature
Antidiuretic 2.3–3.1 pg/mL ↑ in SIADH
hormone ↓ in diabetes insipidus
Urine specific 1.010–1.025 ↓ in diabetes insipidus
gravity
Adrenocorticotropic 120 pg/mL at 6–8 a.m. ↑ in Addison’s disease
hormone ↓ in Cushing’s syndrome, long-
term corticosteroid therapy
test Normal values significance
Cortisol 5–25 g/100 mL ↑ in Cushing’s syndrome, stress
↓ in Addison’s disease, steroid
withdrawal
Vanillylmandelic 0.7–6.8 mg/24 h ↑ in pheochromocytoma
acid (VMA)
test Normal values significance
Fasting plasma 70–100 mg/dL in stress, Cushing’s syndrome
glucose (FPG) FPG 101–125 pre-diabetes
FPG 126 diabetes mellitus
↓ in hypoglycemia, Addison’s
disease
Oral glucose Blood glucose less BG 140–199 at 2 hours pre-
tolerance test than 140 mg/dL at 2 diabetes; BG 200 at 2 hours
hours diabetes mellitus
Glycosylated 4%–7% ↑ in poor diabetes control
hemoglobin
• A thyroid scan may be done to determine the presence of
tumors or nodules.
• A computed tomographic (CT) scan or magnetic resonance
imaging (MRI) may be done to locate a tumor or identify
hypertrophy of a gland.
• Ultrasound may be done of the thyroid or parathyroid glands to
determine if they are enlarged or to find masses.
• Biopsy is done to obtain tissue to examine for possible
cancerous cells.
