Chemistry CLS415 Didactics
Module 1
Introduction to Endocrinology:
Basic Concepts

 Define the following terms:
– Hormone
– Target organ
– Endocrine system
– Exocrine system
– Receptors
 List the major endocrine glands and the hormones they secrete
 Describe the action of hormones in terms of their:
– Regulatory and physiologic functions
– Morphologic action
– Integrative action
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Study of intracellular and extracellular communication by hormones of the endocrine system
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Transmission of Information
 Occurs through several systems or networks
– Nervous System
– Immune System
– Hormonal System
– Others
 Endocrine system is controlled by its linkage with CNS through hypothalamus and pituitary glands
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 A ‘fine-tuned’ communication system

Maintains cellular homeostasis
– Body metabolism
– Growth and development
– Reproduction
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 Chemical messengers
– Interact with target organs by specific receptors
– Illicit biologic response
 Different modes of transport and action
 Example:
Endocrine
Exocrine
Juxtacrine
Neurocrine
Paracrine
Autocrine
Neuroendocrine
Neurotransmission
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Pancreas: insulin Pancreas: amylase & lipase
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 Releasing Hormones (factors)
 Inhibiting Hormones (factors)
Act on anterior pituitary gland
 Produce ADH and Oxytocin
Stored in posterior pituitary gland
Release
Tropic
Hormones
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Stimulating (tropic) Hormones
Stimulating = tropin = trophic = tropic
Stimulating hormones are specific to a particular target organ or target cell
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Stimulating (tropic) Hormones
Gonado tropin : stimulates the gonads
Target gland = testes and ovaries
Thyro tropin : stimulates the thyroid
Target gland = thyroid gland
ACTH = adrenocortico tropic hormone: stimulates the adrenal gland
Target gland = adrenal cortex
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Stimulating (tropic) Hormones
 Stimulating hormones interact with their target glands through receptors
 Membrane receptors:
– Located on the cell membrane
– Interact with protein-type hormones
 Cytoplasmic receptors:
– Located in the cytoplasm of the cell
– Interact with steroid-type hormones
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Endo
Gland
Hormone from endocrine gland
Site of hormone’s action (target)
Biological response of target
Anterior
Pituitary
TSH
ACTH
Thyroid gland Form T3,T4
FSH, LH
Adrenal cortex tropic hormones
Ovary, testis
Form Steroid
Sexual maturation
GH
MSH
Prolactin
Body as a whole
Skin
Mammary glands
Bone/muscle
Darken skin
Lactation
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Pituitary Gland (hypophysis)
Posterior pituitary
Anterior pituitary
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Endo
Gland
Hormone from endocrine gland
Site of hormone’s action (target)
Biological response of target
Posterior
Pituitary
ADH Renal tubules, arterioles
Reabsorb H2O

BP
Oxytocin Uterus,
Breast tissue
Contraction
Milk ejection
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Endo
Gland
Thyroid
Hormone from endocrine gland
T3 and T4
Site of hormone’s action (target)
General body tissue
Biological response of target

O2 consumption,

BMR
Calcitonin
Bone
Inhibits calcium resorption (keeps calcium in bone)
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Endo
Gland
Hormone from endocrine gland
Site of hormone’s action (target)
Biological response of target
Adrenal
Cortex
Steroid hormones:
Cortisol General body tissue
Carbohydrate, protein, fat metabolism
Aldosterone Kidney tubules
(DCT, collecting)
Salt and water balance
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Endo
Gland
Hormone from endocrine gland
Site of hormone’s action (target)
Biological response of target
Adrenal
Medulla
Norepinephrine and
Epinephrine
Sympathetic receptors
Stimulate sympathetic nervous system
Epinephrine =
‘Fight or Flight’ hormone
Liver, muscle, fat
Glycogenolysis, lipolysis
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Regulatory and Physiologic
Functions
 Electrolyte and water balance
– Aldosterone: Na + (and K + , H + )
– ADH: water reabsorption
 Storage and use of nutrients
– Insulin: carbohydrate (glucose) regulation
– Cortisol: carbohydrate, protein, lipid
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 Synthesis of cellular compounds
– Thyroid hormone
– Catecholamines
– Steroid hormones
 Growth and development
– GH (growth hormone)
– Thyroid hormones
– Steroid hormones
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 Sexual maturation and reproduction
– Gonadotropins (LH and FSH)
– Estrogen (female sex hormone)
– Testosterone (male sex hormone)
– HCG (human chorionic gonadotropin)
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No hormone works alone!
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