Anterior Pituitary Gland Functions
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Questions and Answers

What is the primary inhibitory effect of dopamine on prolactin secretion?

  • Inhibits prolactin secretion (correct)
  • Stimulates growth of the thyroid gland
  • Inhibits release of GnRH
  • Stimulates release of TRH

    • Which of the following is a manifestation of excess prolactin secretion in males?

  • Growth of ovarian follicles
  • Infertility due to inhibition of spermatogenesis (correct)
  • Increased testosterone levels
  • Failure of ovulation

    • What regulates the secretion of prolactin by the action of negative feedback?

  • Release of PIH by the hypothalamus (correct)
  • Secretion of GnRH
  • Release of TRH from the pituitary gland
  • Increase in estrogen levels

    • During pregnancy, which hormone works alongside estrogen to stimulate breast development?

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

    What is the role of Thyroid-stimulating hormone (TSH)?

    <p>Stimulates thyroid secretion and growth of the thyroid gland</p> Signup and view all the answers

    Which hormone is secreted by the anterior pituitary and stimulates growth in tissues?

    <p>Growth hormone (GH)</p> Signup and view all the answers

    What is the function of the hypothalamic-hypophysial portal vessels?

    <p>They carry releasing and inhibitory hormones to the anterior pituitary.</p> Signup and view all the answers

    Which of the following is not a tropic hormone secreted by the anterior pituitary?

    <p>Growth hormone (GH)</p> Signup and view all the answers

    What is the primary role of prolactin hormone (PRL)?

    <p>Stimulation of milk production in mammals</p> Signup and view all the answers

    Which hormone secreted by the posterior pituitary is primarily responsible for water reabsorption in the kidneys?

    <p>Antidiuretic hormone (ADH)</p> Signup and view all the answers

    What effect does excess growth hormone have on the body?

    <p>Abnormal growth of bones and tissues</p> Signup and view all the answers

    Which of the following hormones can stimulate the secretion of other hormones in various glands?

    <p>Adrenocorticotropic hormone (ACTH)</p> Signup and view all the answers

    What condition may arise from a deficiency of prolactin hormone (PRL)?

    <p>Failure to lactate</p> Signup and view all the answers

    What is the primary function of Growth Hormone (GH) in the body?

    <p>Stimulating growth to adult size</p> Signup and view all the answers

    How does Growth Hormone (GH) indirectly promote linear growth in long bones?

    <p>By forming somatomedins from the liver</p> Signup and view all the answers

    What effect does Growth Hormone (GH) have on protein metabolism?

    <p>It stimulates protein synthesis in all body cells</p> Signup and view all the answers

    Which substance's mobilization does Growth Hormone (GH) increase during stressful conditions?

    <p>Fatty acids</p> Signup and view all the answers

    Which of the following is a direct effect of Growth Hormone (GH)?

    <p>Inhibiting the uptake of glucose by tissues</p> Signup and view all the answers

    What hormones from the hypothalamus are involved in the regulation of GH secretion?

    <p>Somatostatin and growth hormone-releasing hormone</p> Signup and view all the answers

    Which of the following is NOT a role of Growth Hormone (GH)?

    <p>Enhancing uptake of glucose by peripheral tissues</p> Signup and view all the answers

    What is the chemical nature of Growth Hormone (GH)?

    <p>A single polypeptide chain containing 191 amino acids</p> Signup and view all the answers

    What is the role of GHRH in relation to growth hormone secretion?

    <p>It stimulates the synthesis and secretion of growth hormone.</p> Signup and view all the answers

    How does somatomedins affect growth hormone secretion?

    <p>They inhibit GH secretion directly and stimulate SS production.</p> Signup and view all the answers

    What factor increases GH secretion through the hypothalamus?

    <p>Acute stress</p> Signup and view all the answers

    What is a consequence of growth hormone deficiency before puberty?

    <p>Proportionate decrease in trunk and extremities size</p> Signup and view all the answers

    Which condition is characterized by excess GH secretion before the closure of the epiphysis?

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

    What is a manifestation of acromegaly due to excess GH secretion after epiphysis closure?

    <p>Broader hands and feet</p> Signup and view all the answers

    What is the primary function of prolactin (PRL)?

    <p>Promotes milk production in breasts.</p> Signup and view all the answers

    What is a common result of GH excess in adults?

    <p>Weight gain with muscle fatigue</p> Signup and view all the answers

    Study Notes

    Anterior Pituitary Gland

    • The anterior pituitary, also known as the adenohypophysis, is one of two lobes of the pituitary gland.
    • It secretes five major hormones: growth hormone (GH), prolactin (PRL), thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and adrenocorticotropic hormone (ACTH).
    • ACTH also has melanocyte-stimulating hormone (MSH) activity, affecting melanin production.

    Hypothalamic-Hypophysial Connections

    • Vascular connection (Hypothalamic-Hypophysial portal vessels): Portal vessels connect the primary capillary plexus in the hypothalamus to a secondary capillary plexus in the anterior pituitary. Hypothalamic neurons secrete releasing and inhibitory hormones. These hormones travel via portal vessels to regulate anterior pituitary hormones.
    • Nervous connection (Hypothalamic-Hypophysial tract): Cell bodies of hypothalamic neurons (supraoptic and paraventricular) send axons to the posterior pituitary. Posterior pituitary hormones are synthesized in the hypothalamus and stored for release upon stimulation.

    Hypothalamic Releasing and Inhibitory Hormones

    • These hormones regulate anterior pituitary hormone secretion.
    • Major hormones include corticotropin-releasing hormone (CRH), thyrotropin-releasing hormone (TRH), growth hormone-releasing hormone (GHRH), somatostatin (SS), gonadotropin-releasing hormone (GnRH), and dopamine (PIH).
    • These hormones have specific effects, like CRH stimulating ACTH secretion.

    Growth Hormone (GH)

    • Chemical nature: A single polypeptide chain containing 191 amino acids.
    • Indirect actions:
      • Accelerates skeletal muscle and soft tissue growth (including abdominal and thoracic viscera).
      • Stimulates linear growth of long bones by increasing bone matrix, and calcium and sulfate uptake.
    • Direct actions:
      • Anabolic hormone, stimulating protein synthesis in all body cells.
      • Mobilizes free fatty acids (FFAs) from adipose tissue, providing energy during hypoglycemia, fasting, and stress.
      • Increases blood glucose by inhibiting glucose uptake and utilization by tissues (anti-insulin or diabetogenic effect).
    • Regulation of GH secretion:
      • Hypothalamic regulation: GHRH stimulates GH synthesis and release while somatostatin (SS) inhibits them.
      • Negative feedback by somatomedins: Somatomedins inhibit GH secretion directly and stimulate hypothalamus to produce SS.
      • Sleep: Deep sleep increases GH secretion; bursts decrease with age.
      • Hypoglycemia, exercise, and stress: These stimulate GHRH secretion, increasing GH output.

    Growth Hormone Disorders

    • Dwarfism: GH deficiency before puberty, leading to height below 1-1.2 meters. Causes include anterior pituitary lesions, hypothalamic dysfunction, or GH receptor abnormalities.
    • Gigantism: Excess GH secretion before epiphyseal closure in childhood, resulting in abnormally high stature (exceeds 2 meters). Caused by anterior pituitary tumors.
    • Acromegaly: Excess GH secretion after epiphyseal closure. Causes bone growth in hands, feet, and facial features but does not affect linear growth. Also characterized by soft tissue overgrowth, possible kyphosis, and increased risk of diabetes.

    Prolactin (PRL)

    • Chemical nature: Single polypeptide chain, molecular weight ~22,000.
    • Actions: Stimulates milk production and breast development during pregnancy (with estrogen), while inhibiting ovulation.
    • Regulation:
      • Hypothalamic inhibition by dopamine (PIH). TRH stimulates PRL secretion.
      • Negative feedback: PRL inhibits its own secretion by stimulating PIH release.

    PRL Disorders

    • PRL deficiency: Failure of lactation.
    • PRL excess: Caused by prolactin-secreting tumors. In females, this can result in galactorrhea (excessive milk production) and infertility due to ovulation failure. In males, this can inhibit spermatogenesis.

    Tropic Hormones

    • These hormones (TSH, FSH, LH, and ACTH) stimulate hormone production in other endocrine glands.
    • TSH: Stimulates thyroid hormone secretion and growth.
    • FSH: Stimulates ovarian follicle growth in females and spermatogenesis in males.
    • LH: Stimulates ovulation in females and testosterone secretion in males.
    • ACTH: Stimulates steroid hormone production in the adrenal cortex. Has MSH activity.

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    Description

    Test your knowledge on the anterior pituitary gland and its hormone secretion, including growth hormone and adrenocorticotropic hormone. This quiz also covers the hypothalamic connections that regulate the anterior pituitary. Challenge yourself with questions on this essential endocrine system topic.

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