Endocrinology: Pituitary Gland Overview
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Questions and Answers

What effect does growth hormone have on electrolyte metabolism?

  • Increase excretion of Na+, K+, and HPO4++
  • Increase Ca++ absorption from GIT (correct)
  • Decrease absorption of Ca++ from GIT
  • Control secretion of insulin

    • Which of the following factors increases growth hormone secretion?

  • Exogenous GH
  • Blood glucose (correct)
  • Fasting (correct)
  • Obesity

    • What condition is characterized by decreased growth hormone secretion before the union of the epiphysis?

  • Hyperplasia
  • Gigantism
  • Acromegaly
  • Pituitary dwarfism (correct)

    • What is one of the manifestations of gigantism?

    <p>Proportionate long stature</p> Signup and view all the answers

    Which hormone stimulates milk formation and secretion during lactation?

    <p>Prolactin</p> Signup and view all the answers

    Which of the following is a manifestation of acromegaly?

    <p>Increased thickness of bones</p> Signup and view all the answers

    How does obesity affect growth hormone secretion?

    <p>It decreases GH secretion</p> Signup and view all the answers

    What causes the over secretion of growth hormone leading to gigantism?

    <p>Adenoma of GH-secreting cells</p> Signup and view all the answers

    What effect does oxytocin have on the uterus during labor?

    <p>It stimulates uterine contraction.</p> Signup and view all the answers

    Which hormone can inhibit ovulation in lactating women?

    <p>Prolactin</p> Signup and view all the answers

    What is the main function of antidiuretic hormone (ADH) on the kidneys?

    <p>Increases water reabsorption.</p> Signup and view all the answers

    What effect does decreased extracellular fluid volume have on ADH secretion?

    <p>Stimulates ADH secretion.</p> Signup and view all the answers

    Which of the following factors decreases ADH secretion?

    <p>Cold weather</p> Signup and view all the answers

    What is a possible manifestation of hyposecretion of ADH (Diabetes insipidus)?

    <p>Dehydration.</p> Signup and view all the answers

    What structural changes can lead to hyposecretion of ADH?

    <p>Destruction of hypothalamic nuclei.</p> Signup and view all the answers

    Which hormone is involved in the development of the prostate and seminal vesicles in males?

    <p>Luteinizing hormone</p> Signup and view all the answers

    What is the primary function of growth hormone on bone growth?

    <p>Increase Ca++ uptake for cartilage calcification</p> Signup and view all the answers

    Which hormone is secreted by the anterior pituitary and has a direct metabolic function?

    <p>Prolactin</p> Signup and view all the answers

    Which of the following hormones has a trophic function?

    <p>Gonadotrophic hormones (GTH)</p> Signup and view all the answers

    What effect does growth hormone have on lipid metabolism?

    <p>Promotes ketonemia</p> Signup and view all the answers

    Which structure connects the hypothalamus to the posterior pituitary?

    <p>Hypothalamo-hypophyseal portal tract</p> Signup and view all the answers

    What is the effect of growth hormone on protein metabolism?

    <p>Increases amino acid uptake and protein synthesis</p> Signup and view all the answers

    What is the main effect of growth hormone on carbohydrate metabolism?

    <p>Increases glycogenolysis</p> Signup and view all the answers

    Which hormone is NOT produced by the anterior pituitary gland?

    <p>Oxytocin</p> Signup and view all the answers

    Study Notes

    Pituitary Gland

    • Located in the hypophyseal fossa (sella turcica)
    • Connected to the hypothalamus through the hypothalamo-hypophyseal portal circulation and tract
    • Anterior pituitary (adenohypophysis) is regulated by the hypothalamus through hormones released and inhibited in the portal circulation
    • Posterior pituitary (neurohypophysis) is regulated by the hypothalamus through the hypothalamo-hypophyseal tract releasing ADH and oxytocin.

    Anterior Pituitary

    • Secretes hormones with direct metabolic function:
      • Growth hormone (GH)
      • Prolactin
    • Secretes hormones with trophic function:
      • Thyroid stimulating hormone (TSH)
      • Adrenocorticotrophic hormone (ACTH)
      • Gonadotrophic hormones (GTH):
        • Luteinizing hormone (LH)
        • Follicle Stimulating Hormone (FSH)
    • Secretion of anterior pituitary hormones are controlled by hypothalamic and feedback mechanisms

    Growth Hormone (GH)

    • Effect on growth:

      • Stimulates bone growth by increasing proliferation of epiphyseal cartilage, Ca++ uptake, and calcification and mineralization of bone.
      • Stimulates soft tissue growth by increasing the growth of skeletal muscle and all organs.

    • Effect on metabolism:

      • Carbohydrate: hyperglycemic and diabetogenic; decreases glucose uptake and utilization, increases gluconeogenesis and glycogenolysis in the liver.
      • Protein: protein anabolic; increases amino acid uptake by cells, increases transcription and translation to increase protein synthesis.
      • Lipid: lipolytic and ketogenic; increases lipolysis leading to increased plasma FFA (lipemia), increases FFA oxidation in the liver leading to ketone bodies (ketonemia).
      • Electrolyte: increases Ca++ absorption from the gastrointestinal tract and decreases excretion of Na+, K+, and HPO4++.

    • Control of Secretion:

      • Hypothalamic:
        • Growth hormone-releasing hormone (GHRH)
        • Growth hormone-inhibiting hormone (GHRIH) or somatostatin
      • Feedback:
        • Negative short loop feedback by GH on the hypothalamus (GHRH)

    • Other Factors affecting GH:

      • Increase GH: blood glucose and FFA, proteins in diet, fasting, exercise, stress
      • Decrease GH: blood glucose and FFA, proteins in diet, obesity, exogenous GH

    Abnormal GH Secretion

    • Diseases Related to Abnormal Growth Hormone:
      • Decreased Secretion:
        • Before Puberty: Pituitary dwarfism
        • After Puberty: No significant impact
      • Over Secretion:
        • Before Puberty: Gigantism
        • After Puberty: Acromegaly

    Pituitary Dwarfism

    • Decreased GH secretion before union of the epiphysis
    • Causes: Decreased GH secretion from the anterior pituitary.
    • Manifestations:
      • Symmetrical skeletal growth retardation, proportionate short stature.
      • Soft tissue growth retardation.
      • Normal mentality and sexuality.
      • Facial features: Childish face with small lips and nose.

    Gigantism

    • Over secretion of GH before union of the epiphysis
    • Causes: Adenoma of cells secreting GH in the anterior pituitary.
    • Manifestations:
      • Symmetrical overgrowth of long bones, proportionate long stature.
      • Soft tissue overgrowth.
      • Hypogonadism.
      • Pituitary diabetes (insulin insensitive).

    Acromegaly

    • Over secretion of GH after union of the epiphysis
    • Causes: Adenoma of cells secreting GH in the anterior pituitary.
    • Manifestations:
      • Increased thickness of short bones (hands and feet).
      • Overgrowth of all soft tissues and visceromegaly.
      • Kyphosis due to enlargement of the vertebrae.
      • Facial features: Big skull, depressed and enlarged nose, forward protrusion of enlarged mandible.
      • Pituitary diabetes (insulin insensitive).

    Prolactin Hormone

    • Secreted from the anterior pituitary gland.
    • Female:
      • Stimulates milk formation (lactogenesis) and secretion during lactation:
        • Secreted 2-3 days after labor.
        • Stimulates mammary glands to synthesize casein, fat, and lactose.
      • Inhibits ovulation in lactating women by inhibiting GTH of the pituitary or GnRH of the hypothalamus.
    • Male:
      • Stimulates development of cells in the testis in the pre-pubertal period.
      • Involved in the development of the prostate and seminal vesicle.

    Posterior Pituitary (Neurohypophysis)

    • Hormones stored by posterior pituitary:
      • Antidiuretic hormone (ADH)
      • Oxytocin

    Antidiuretic Hormone (ADH, Vasopressin)

    • Synthesized mainly in the nuclei of the hypothalamus.

    • Functions:

      • Kidney: Acts on V2 receptors on the basal border of cells in the distal convoluted tubule (DCT) of the kidney. Increases water reabsorption, leading to water retention in the body, and production of concentrated urine.
      • Blood Vessels:
        • Physiological dose: No effect on blood vessels.
        • Pharmacological dose: Acts on V1A receptors on blood vessels, causing direct vasoconstriction of all blood vessels.
      • Smooth Muscles:
        • Direct action like oxytocin on smooth muscles of the uterus and small intestine.

    • Regulation of Secretion:

      • ECF Volume: Decreased ECF volume stimulates the hypothalamus to secrete ADH.
      • ABP: Decreased ABP stimulates the hypothalamus to secrete ADH.
      • ECF Osmolarity: Increased osmolarity > 300 m osmol/l (dehydration) stimulates osmo-receptors in the hypothalamus, increasing ADH secretion.

    • Other Factors Affecting ADH:

      • Increase ADH: Hot weather, Nicotin, Morphine
      • Decrease ADH: Cold weather, Opiates, Ethyl Alcohol

    Hyposecretion of ADH (Diabetes Insipidus)

    • Decreased ADH secretion
    • Causes:
      • Destruction of the hypothalamic nuclei or their axons.
      • Failure of the kidney to respond to ADH.
    • Manifestations:
      • Polyuria (excessive urination)
      • Polydipsia (excessive thirst)
      • Loss of water-soluble vitamins due to the polyuria
      • Increase in the basal metabolic rate (BMR)

    Oxytocin

    • Synthesized mainly in the nuclei of the hypothalamus, similar to ADH.
    • Functions:
      • Female:
        • Labor: Stimulates contraction of the uterus directly.
        • Postpartum: Stimulates involution of the uterus (return to normal size), assists in the descent of the placenta, and helps prevent postpartum hemorrhage.

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    Description

    Explore the fascinating workings of the pituitary gland with this quiz. Learn about its structure, how it connects to the hypothalamus, and the various hormones it releases, including growth hormone and categorization of its functions. Test your understanding of the anterior and posterior pituitary's roles in regulating body functions.

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