THE PITUITARY

GLAND

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INTRODUCTION

• The pituitary gland or Hypophysis Cerebri is an ovoid structure of about 0.5 gm in adults.

• It is connected to the brain through a stalk called Infundibulum.

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Division in Two Lobes

• The pituitary is divided into two lobes.

• The anterior

Pituitary.

• The Posterior Pituitary.

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The Anterior Pituitary• Hypothalamus (a region of brain) controls

the anterior pituitary by producing:

• The Releasing Hormone:

Stimulates the release of pituitary hormones.

• The Inhibiting Hormone:

Inhibits the release of pituitary hormones.

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Releasing & Inhibiting Hormones

• RH and IH are produced in the cell bodies of neurosecretory neurons.

• They are stored in the ends of the axons(present just above the pituitary) until needed.

• When released, the hormones diffuse into capillaries draining into veins which in turn drain into capillaries of pituitary.

• They then bind to the target cells causing them to release hormones.

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Hormone Major target organ(s) Major Physiologic Effects

AnteriorPituitary

Growth hormoneLiver, adipose

tissuePromotes growth (indirectly), control of protein, lipid and carbohydrate metabolism

Thyroid-stimulating hormone

Thyroid gland Stimulates secretion of thyroid hormones

Adrenocorticotropic hormone

Adrenal gland (cortex)

Stimulates secretion of glucocorticoids

Prolactin Mammary gland Milk production

Luteinizing hormone Ovary and testis Control of reproductive function

Follicle-stimulating hormone

Ovary and testis Control of reproductive function

PosteriorPituitary

Antidiuretic hormone Kidney Conservation of body water

Oxytocin Ovary and testisStimulates milk ejection and uterine

contractions

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THE GROWTH HORMONE

• Protein hormone produced by anterior pituitary under the control of hypothalamus.

• Production through negative feedback mechanism.

• The quantity is greatest during childhood and adolescence.

• The highest blood levels are during sleep and strenous exercise.

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ACTION 0f GH

• GH stimulates growth in the body by promoting:

• Cellular Enlargement – Hypertrophy. and• Increase in the number of cells through

division – Hyperplasia.• It acts primarily on bones and muscles.

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ACTION 0f GH

• In Bones: It stimulates cell division and protein

synthesis resulting in an increase in the length and width of bones.

• In Muscles: It increases uptake of amino acids and

synthesis of proteins.

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EFFECTS 0f GH

• DAWARFISM - Under-secretion

during growth phase of a child is one cause of stunted growth.

- Characterized by small stature.

- World’s smallest girl due to Dawarfism. (weighed 2 lbs, 8 ounces when she was born)

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EFFECTS 0f GH

• GIGANTISM:

- Over-secretion during growth phase results in gigantism.

- Giants usually have poor health.

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EFFECTS 0f GH

• ACROMAGELY:

- Over-secretion after growth phase results in acromagely.

- Feets, hands and face become overly large.

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References

• Human Biology , Daniel D. Chiras , Sixth Edition.

• Human Biology , Sylvia S.Madar , Magraw Hill , International Eleventh Edition.