ENDOCRINE SYSTEM

Objectives

     Describe the functions of the endocrine glands and there hormones.

Describe the relationship between the hypothalmus and the pituitary glands. Identify the diagnostic tests used to determine alterations in function in each of the endocrine glands.

Compare hyper/hypo pituitarism (thyroidism, parathyroidism, Addison’s, Cushing syndrome, gigantism, dwarfism, SIADH, diabetes insipidus), causes, clinical manifestations, management and nursing interventions. Identify teaching of patients needing steroid therapy.

Required Reading

   Smeltzer & Bare (2004) Chapter 42 Readings on reserve: Unit IV Endocrine http://arbl.cvmbs.colostate.edu/hbooks/pa thphys/endocrine/index.html

( Excellent web-site)

Endocrine System

 The endocrine system ( endo, comprised of glands that secrete hormones that are carried by the blood to act on target tissue, regulating multiple body processes. (ductless) within) is  The endocrine, nervous and immune system work together to create a precise control over all body organs and metabolic processes.

Hormones

 Defined as chemical substances synthesized and secreted by a specific organ or tissue, carried by the blood stream to other cells or organs, to produce a particularl regulatory effect.

(Lewis, Heitkemper & Dirksen, 2004)

Principal functions of the endocrine system

   Maintenance of the internal environment in the body (maintaining the optimum biochemical environment).

Integration and regulation of growth and development.

Control, maintenance and instigation of sexual reproduction, including gametogenesis, coitus, fertilization, fetal growth and development and nourishment of the newborn.

The Endocrine & Nervous System

  The effects of hormones secreted by the endocrine system affect the nervous system and are in turn mediated by the nervous system.

Example: adrenal medulla secretes substances – epinephrine & norepinephrine – that act as neuro transmitters causing an effect of the sympathetic nervous system.

Nervous system

The nervous system

exerts point-to-point control through nerves, similar to sending messages by conventional telephone. Nervous control is electrical in nature and fast.

Hormones travel via the bloodstream to target cells

•

The endocrine system

sends its hormonal messages to essentially all cells by secretion into blood and extracellular fluid. Like a radio broadcast, it requires a receiver to get the message - in the case of endocrine messages, cells must bear a

receptor

for the hormone being broadcast in order to respond.

Endocrine System & Immune System

  There is also close interaction between the endocrine and immune systems.

Example: Glucocorticoids play a major role in the body’s response to stress.

PRINCIPAL ENDOCRINE GLANDS

   Pituitary Adrenal Thyroid   Parathyroid Glands Pancreas  Gonads (ovaries & testes) (Hypothalamus link b/t nervous & endocrine systems)

Endocrine Glands Glands

    

Pineal gland

sleep cycle.

Secretes melatonin, a hormone that helps regulate wake-

Hypothalmus

hormones.

: primary link btw. the endocrine and nervous system. It controls the release of pituitary

Pituitary (anterior & posterior):

the “master gland b/c of its importance.

Thyroid

: Causes increase in metabolic rate, increase in protein and bone turnover.

Parathyroids

: (4) regulate serum calcium & phosphate.

   

Thymus

: Secretes hormones that maintain and contribute to the production of peripheral t-cell population.

Adrenal glands

nervous system. (cortex & medulla) Cortex secretes glucocorticoids (cortisol), mineralcorticoids (aldosterone) and androgens.Medulla secretes substances that act as neurotransmitters on sympathetic

Pancreas

: endocrine and exocrine functions Endocrine functions carried out by the Islets of Langerhan which produce insulin and glucagon (regulate blood glucose levels). Exocrine cells secrete digestive enzymes into the small intestine.

Gonads

– female ovaries in abdomen; male testes in scrotum

Other Structures Producing Hormones

•Glands within the gastro intestinal tract •Structures within the heart and blood vessels (atrial natriuretic peptide/factor (ANF

or

ANP) •Kidney: renin & erythropietin

A cell is a target for a hormone because is has a specific receptor for that hormone Most hormones circulate in blood, coming into contact with essentially all cells. However,

a given hormone usually affects only a limited number of cells, which are called target cells . A target cell responds to a hormone because it bears receptors for the hormone.

Hormones -Three classes based on structure 1.

2.

3.

Steroid Peptide (protein) Amines

Mechanism of Protein Hormone

• Are water soluble • Bind to cell membrane receptors on target tissue and activate second messenger within.

•Rapid response time

Peptide (Protein) Hormones

Steroid Hormones

 Steroid hormones pass through the plasma membrane & do not require an external receptor.

Hormones exert their actions in four ways: 1. Maintenance of internal environment 2. Regulation of energy availability 3. Reproduction 4. Growth & development

1. Maintenance of internal environment is done through such activities as: • • • Control of extracellular fluid volume & BP Electrolyte regulation Maintenance of bone, muscle & fat stores

2. Regulation of energy available

   Control of the conversion of calories to energy Storage of energy Mobilization of energy stores when needed

3. Reproduction

  Ovaries: produce ova and hormones estrogen & progesterone & are controlled by pituitary. Testes: produce the male reproductive cells spermatozoa and the male hormones testosterone and inhibin

4

.

Growth and Development



Anterior pituitary secretes growth hormone



Review Peds

Feedback Control

 Hormone concentration in the blood stream is maintained at a fairly constant level. When hormone levels rise, further production of the hormones is inhibited. When the hormone level drops, the rate of production increases.

Feedback control

  Negative feedback is most common. The gland itself responds by increasing or decreasing hormone levels based on feedback from various factors.

Positive feedback is less common: The increased activity of hormone production and response stimulates further production.

The regulation of hormone levels depend mainly on the body’s negative feedback system. For example:     Elevated blood sugar levels stimulate the release of insulin from the pancreas. The insulin facilitates the transfer of sugar from the blood to the cells Low BS inhibits the release of more insulin Negative feedback is the corrective action

Feedback Control of Hormone Production Feedback loops are used extensively to regulate secretion of hormones in the hypothalamic-pituitary axis. An important example of a negative feedback loop is seen in control of thyroid hormone secretion

Positive Feedback

   The regulation of hormone levels also depend on the body’s positive feedback system Positive feedback systems amplify changes rather than reversing them For example: During labour, muscle contractions becomes stronger & stronger under the influence of oxytocin

Diseases of the endocrine system are related to either:

  an

excess or a deficiency

hormone or of a specific to a deficit in the receptor site.

The thyroid and testes are the only glands that can be examined directly Knowledge of A&P together with data from the history & lab tests are essential in assessing the endocrine system.

Hypo and Hypersecretion of Hormones



Hyper-secretion is production of too much hormone



Hypo-secretion is production of too little hormone

Endocrine Disorders & Psychiatric Disturbances

Gland Hypo Hyper Pituitary Thyroid Parathyroid Myxedema Dwarfism Sex Dysfunction Diabetes Insipidus Cretinism Myxedema Tetany Gigantism Acromegaly Sexual Dysfunction Graves Hypercalcemia Adrenal Pancreas Addison’s Disease Diabetes Mellitus Cushing Disease Hyperaldosteronism Hypoglcemia

  Endocrine disorders may be associated with a wide range of psychological/psychiatric symptoms such as depression, mania, paranoid disorders, cognitive disturbances, hostility, & irritability. Nurses need to be aware that such symptoms and/ may precede other manifestations of an endocrine disorder or be early indications of its relapse.

Endocrine Disorders Commonly Manifesting Psychiatric Characteristics       Cushing’s Disease Addison’s Disease Hyperthyroidism Hypothyroidism Hyperprolactinaemia Hyperparathyroidism

Hypothalamus and Pituitary as Partners

HYPOTHALMUS

 Coordinates the working of the autonomic nervous system & endocrine system. Receives info from cerebral hemisphere, brain stem, spinal cord, autonomic & peripheral nerves, senses.

Hypothalamus Function

  Produces regulatory hormones that stimulate the anterior pituitary (especially stimulating or inhibiting): TRH, GHRH, GnRH, GH-IH, CRH, PRH, PIH Ultimately the hypothalamus can control every endocrine gland in the body!

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Hypothalamic Hormones

Releasing Factor Anterior Pituitary Target Cells

TRH TSH thyroid GHRH GH bone muscle GH-IH GH bone muscle GnRH CRH FSH, LH ACTH ovaries, testes Adrenal cortex PRH Prolactin mammary glands PIH (dopamine inhibitor)

          HYPOTHALMUS: SOME MAJOR FUNCTIONS Autonomic nervous system Secretion of pituitary hormones Organization of body metabolism Availability of energy foods such as glucose sleep & wakefulness Temperature, thirst & water regulation Hunger & Appetite Behavior - fear, rage, sexual desire Growth Sexual reproduction

•

Assess

Hypothalamus Pituitary



Partners

Due to the unique interaction between the hypothalamus and the pituitary gland,

hypothalamic dysfunction is often associated with alterations in pituitary function.

Because the hypothalamus is also responsible for many homeostatic regulatory functions, alterations can also occur in behavior, temperature control &, appetite.

Hypothalmus: disturbance in function may be triggered by: •Mental or emotional upset, grief & worry •Weight changes (drastic) •Other causes - tumors, •cerebral infections, trauma.