Hypothalamus and Pituitary

FunctionChemistry CLS415

Didactics

Module 1Introduction to

Endocrinology: Basic Concepts

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Objectives: Define the following terms:

– Hormone– Target organ– Endocrine system

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

– Exocrine system– Receptors

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What is Endocrinology?

Study of intracellular andextracellular communication byhormones 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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The Endocrine System

A ‘fine-tuned’ communication system

Maintains cellular homeostasis– Body metabolism– Growth and development– Reproduction

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Major Endocrine Glands

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Hypothalamus

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What are Hormones? Chemical messengers

– Interact with target organs by specific receptors

– Illicit biologic response Different modes of transport and action Example:

Endocrine ParacrineExocrine AutocrineJuxtacrine NeuroendocrineNeurocrine Neurotransmission

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Endocrine vs Exocrine

Pancreas: insulin Pancreas: amylase & lipase

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Hypothalamus Releasing Hormones (factors) Inhibiting Hormones (factors)

Produce ADH and Oxytocin

Stored in posterior pituitary gland

Act on anterior 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

Gonadotropin: stimulates the gonadsTarget gland = testes and ovaries

Thyrotropin: stimulates the thyroidTarget gland = thyroid gland

ACTH = adrenocorticotropic 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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tropic hormones

Table, page 2 of handoutEndo Gland

Hormonefrom endocrine gland

Site of hormone’s action (target)

Biological response of target

Anterior Pituitary

TSH

ACTH

FSH, LH

GH

MSH

Prolactin

Thyroid gland

Adrenal cortex

Ovary, testis

Body as a whole

Skin

Mammary glands

Form T3,T4

Form Steroid

Sexual maturation

Bone/muscle

Darken skin

Lactation

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Pituitary Gland (hypophysis)

Posteriorpituitary

Anteriorpituitary

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Table, page 2 of handout

Endo Gland

Hormone from endocrine gland

Site of hormone’s action (target)

Biological response of target

Posterior Pituitary

ADH

Oxytocin

Renal tubules, arterioles

Uterus, Breast tissue

Reabsorb H2O BP

ContractionMilk ejection

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Table, page 2 of handout

Endo Gland

Hormone from endocrine gland

Site of hormone’s action (target)

Biological response of target

Thyroid T3 and T4

Calcitonin

General body tissue

Bone

O2 consumption, BMR

Inhibits calcium resorption (keeps calcium in bone)

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Table, page 2 of handout

Endo Gland

Hormone from endocrine gland

Site of hormone’s action (target)

Biological response of target

Adrenal

Cortex Steroid hormones:

Cortisol

Aldosterone

General body tissue

Kidney tubules

(DCT, collecting)

Carbohydrate, protein, fat metabolism

Salt and water

balance

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Table, page 2 of handoutEndo Gland

Hormone from endocrine gland

Site of hormone’s action (target)

Biological response of target

Adrenal

Medulla Norepinephrine and Epinephrine

Epinephrine =‘Fight or Flight’ hormone

Sympathetic receptors

Liver, muscle, fat

Stimulate sympathetic nervous system

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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Morphogenic Action

Synthesis of cellular compounds– Thyroid hormone– Catecholamines– Steroid hormones

Growth and development– GH (growth hormone)– Thyroid hormones– Steroid hormones

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Morphogenic Action Sexual maturation and

reproduction– Gonadotropins (LH and FSH)– Estrogen (female sex hormone)– Testosterone (male sex hormone)– HCG (human chorionic

gonadotropin)

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Integrative Action

No hormone works alone!

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Integrative Action