Oxytocin Receptors and Uterine Smooth Muscle
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Questions and Answers

How does the amino acid sequence of oxytocin differ from that of vasopressin?

  • It differs at positions 4 and 9
  • It differs at positions 2 and 7
  • It differs at positions 1 and 5
  • It differs at positions 3 and 8 (correct)

    • What is the effect of endogenous oxytocin on uterine smooth muscle during the second half of pregnancy?

  • It decreases the expression of oxytocin receptors
  • It does not affect the sensitivity of uterine smooth muscle
  • It increases the expression of oxytocin receptors and makes the muscle more sensitive (correct)
  • It increases the expression of oxytocin receptors and makes the muscle less sensitive

    • How is oxytocin administered for labor initiation and augmentation?

  • Orally
  • Intravenous (correct)
  • Subcutaneously
  • Topically

    • Where is oxytocin eliminated from the body?

    <p>Kidneys &amp; Liver</p> Signup and view all the answers

    What is the half-life of oxytocin?

    <p>5 minutes</p> Signup and view all the answers

    How does oxytocin act on uterine smooth muscle?

    <p>It acts through G protein-coupled receptors to contract the muscle</p> Signup and view all the answers

    What is the clinical indication for oxytocin?

    <p>Control of postpartum bleeding</p> Signup and view all the answers

    What does oxytocin stimulate the release of to augment uterine contraction?

    <p>Prostaglandins and leukotrienes</p> Signup and view all the answers

    What is the effect of iodide therapy on a hyperplastic thyroid gland?

    <p>Decreases the size and vascularity of the gland</p> Signup and view all the answers

    What is the clinical indication for using iodide therapy in cases of thyroid storm?

    <p>Management of hypermetabolic state caused by excessive release of thyroid hormones</p> Signup and view all the answers

    What is a disadvantage of iodide therapy in relation to thioamide therapy?

    <p>It delays the onset of thioamide therapy</p> Signup and view all the answers

    Why should chronic use of iodides be avoided in pregnancy?

    <p>Because they can cause fetal goiter</p> Signup and view all the answers

    Which isotope is used for the treatment of thyrotoxicosis?

    <p>131I</p> Signup and view all the answers

    What are the adverse reactions to iodine known as?

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

    What effect does iodide therapy have on intraglandular stores of iodine?

    <p>It increases intraglandular iodine stores</p> Signup and view all the answers

    Which of the following hormones is an antagonist of the oxytocin receptor and has been approved as a treatment for preterm labor?

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

    What is the active metabolite of Carbimazole?

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

    What is the effect of iodide therapy on the onset of radioactive iodine therapy?

    <p>It delays the onset of radioactive iodine therapy</p> Signup and view all the answers

    Which condition is due to defects in the thyroid gland itself and is the most common cause of hypothyroidism?

    <p>Primary Hypothyroidism</p> Signup and view all the answers

    What is NOT a toxicity associated with Thioamides?

    <p>Grave’s Disease</p> Signup and view all the answers

    Which of the following is NOT a use of 131I?

    <p>Thyroid storm</p> Signup and view all the answers

    What is the most common cause of hyperthyroidism?

    <p>Grave’s Disease</p> Signup and view all the answers

    What is the primary mechanism of action of agonistic GnRH analogues?

    <p>Profound suppression of LH and FSH</p> Signup and view all the answers

    What is the half-life of intravenously administered GnRH analogs?

    <p>4 minutes</p> Signup and view all the answers

    Which route of administration is NOT used for GnRH analogs?

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

    What is the duration of clinical uses for GnRH analogs in cases of controlled ovarian stimulation?

    <p>A few days</p> Signup and view all the answers

    What is the effect of prolonged activation of GnRH receptors by GnRH?

    <p>Desensitization of pituitary G protein coupled receptors</p> Signup and view all the answers

    All are clinical indications of GnRH except?

    <p>Controlled ovarian stimulation</p> Signup and view all the answers

    What is the route of administration for Nafarelin?

    <p>Nasal spray</p> Signup and view all the answers

    Which hormone is responsible for the cyclical changes in estrogen and progesterone concentrations during the menstrual cycle?

    <p>Gonadotropin-releasing hormone (GnRH)</p> Signup and view all the answers

    What is the primary mechanism through which ovarian suppression induced by continuous treatment with a GnRH agonist reduces estrogen and progesterone concentrations?

    <p>Inhibition of the release of GnRH from the hypothalamus</p> Signup and view all the answers

    What is the temporary effect of GnRH agonists on uterine leiomyomas (fibroids) when treatment is stopped?

    <p>Gradual recurrent growth to previous size</p> Signup and view all the answers

    What is the primary characteristic of uterine leiomyomata/fibroids that makes them responsive to treatment with a GnRH agonist?

    <p>Estrogen sensitivity</p> Signup and view all the answers

    What is the clinical use of GnRH agonists in the treatment of uterine leiomyomas (fibroids)?

    <p>Preoperative treatment to reduce fibroid size</p> Signup and view all the answers

    What is the primary impact of ovarian suppression induced by continuous treatment with a GnRH agonist on cyclical abdominal pain in premenopausal women with endometriosis?

    <p>Reduced exposure to cyclical changes in estrogen and progesterone</p> Signup and view all the answers

    How does continuous treatment with a GnRH agonist impact estrogen and progesterone concentrations?

    <p>Reduces estrogen and progesterone concentrations</p> Signup and view all the answers

    What is the result of treatment for 3–6 months with a GnRH agonist in terms of fibroid size?

    <p>Reduction in fibroid size</p> Signup and view all the answers

    What is the role of atosiban in the treatment of preterm labor?

    <p>It acts as an oxytocin receptor antagonist</p> Signup and view all the answers

    Which condition is a contraindication for the use of atosiban?

    <p>Fetal malpresentation</p> Signup and view all the answers

    What is the mechanism of action of desmopressin acetate (DDAVP)?

    <p>It is a long-acting synthetic analog of vasopressin</p> Signup and view all the answers

    What are the properties of vasopressin?

    <p>Antidiuretic and vasopressor</p> Signup and view all the answers

    Why did the FDA decide not to approve atosiban in 1998?

    <p>Due to concerns about efficacy and safety</p> Signup and view all the answers

    What is the primary role of oxytocin during the immediate postpartum period?

    <p>To augment uterine contractions and stop vaginal bleeding</p> Signup and view all the answers

    In response to what physiological changes is vasopressin released by the posterior pituitary?

    <p>Rising plasma tonicity or falling blood pressure</p> Signup and view all the answers

    What is the antidiuretic-to-pressor ratio of desmopressin acetate (DDAVP) compared to vasopressin?

    <p>$4000:1$</p> Signup and view all the answers

    What is the role of desmopressin acetate (DDAVP) in relation to pressor activity?

    <p>$4000$ times less pressor activity than vasopressin</p> Signup and view all the answers

    What is the primary role of vasopressin in the body?

    <p>Regulation of plasma tonicity and blood pressure</p> Signup and view all the answers

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