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The term endocrine denotes internal

secretion of biologically active substance

called hormone

The term exocrine denotes secretion

outside the body e.g through sweatglands or ducts that lead into the GI tract.

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There is a tight coupling between the

basic science of endocrinology and

clinical medicine

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The endocrine and nervous systems

are the major controllers

of the flow of information

between

different cells and tissues

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Traditional definition

The endocrine system releases

chemical mediators termed hormonesinto the circulation for actionaway from their sites of origin.

This definition becomes blurred

because the recoqnition thatthe circulating hormones can also havelocal effects in the cells in which they are synthetized ( autocrine)or

in adjacent cells after diffusion (paracrine)oracts inside the cell without being released (intracrine)

e.g insulin (inhibits its own release)

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Hormone Released Transported

Target

bind to receptors

on the cell surface intracellular (nuclear)

e.g Insulin Steroid

GH Thyroid hormones

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RECEPTORS BIFUNCTIONAL

1. Recognition

2. Signal activation

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Hormone antagonism

Certain hormones antagonize the effects of

other hormones.

It is necessary to know the value of each

hormone to interpret the clinical phenomenon

N Testosteron

Estrogen

N Estrogen

Testosteron

GYNECOMASTIA

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The function of hormones

There are 4 domain :

Reproduction Growth and development

Maintenance of the internal environment

Energy production, utilization and storage

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CHEMICAL COMPOSITIONOF HORMONES

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MECHANISM OF HORMONE ACTION

Hormone receptors

Cell surface receptors

Nuclear receptors

Hormone effects on receptor activity

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CLASSESOF HORMONE ACTION

Classification of hormone action by receptor type

Glucocorticoid CH regulating activities

Mineralocorticoid Salt regulating activity

Classification of hormone action by ligand typeAgonist

Partial agonist-partial antagonist

Antagonist

Inactive compounds

Mixed agonist-antagonist

Ligands with Reserve Pharmacology

Mechanisms of ligand action

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MODULATIONOF HORMONE LEVELS

Hormone synthesis

Regulation of hormone production

There are a number of patterns of regulation

of hormone release:1. The hypothalamic-pituitary-target gland2. Free standing endocrine glands (parathyroid,

islet cells )3. Pulsatile release etc

Hormone transport in the circulation

BoundFree

Transport of hormones across the membrane

Metabolism & elimination of hormones

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DISORDERSOF THE ENDOCRINE SYSTEM

Arise from :

Excess of hormones

Deficiency of hormones

Resistance to hormones

Specific tumorsIatrogenic syndromes

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Hypofunction

Destruction of the gland:

Auto immune diseaseType 1 diabetesHypothyroidismAdrenal insufficiency

IschaemiaTumorInflammationHaemorrhage

Extraglandular disorders

Damage to tissues thatconvert hormonr precursor to active form

e.gRenal disease

Defective conversion of25(OH)D3 1,25 (OH) D3

abnormalities in Ca & phosphate balance

Defects in hormone biosynthesis

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Endocrine hyperfunction

Results usually from :

Tumors

Hyperplasia

Autoimmune stimulation

Ectopic production of hormones by tumors

Defects in sensitivity to hormonesSyndromes of hormone excess due toadministration of exogenous hormone

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Glands that produce hormones are scattered allover the bodys tissue but glands that areconsidered to be the principal glands are

- the hypophysis (pituary)

- the thyroid gland- the parathyroid glands- the adrenasls- isletsof Langerhans- the gonads

Many other (new) hormones are beingdiscovered

Principal glands

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APPROACHTO THE PATIENTWITH ENDOCRINE DISEASE

Evidence-based endocrinology

History & physical examination

Laboratory studies

-

Measurement of hormonal levels: basal level- Plasma & urine analysis- Free hormone ;evels- Immune assays- Biopsy

Screening for endocrine diseases

Clinical interpretation of laboratory test

Treatment of endocrine diseases

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Laboratory testing of Endocrine Function

It is worthwhile to review ; anda considerable judgmentis required,

because of :

Pulsatile hormone secretionDiurnal variation

Cyclic variation

Age

Sleep entrainmentHormone antagonism

Dynamic testing

Hormone and metabolite interaction

Protein binding

Laboratory error

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Cases to be discussed as to trigger the studentsto learn the endocrine-metabolism system are :

Disorders of :

* The hypophysis

* Tahe thyroid gland

* The calcium metabolism

(concerning the parathyroid gland)

* The adrenals

* The islets of Langerhans* The gonads

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