47 Questions
How does the amino acid sequence of oxytocin differ from that of vasopressin?
It differs at positions 3 and 8
What is the effect of endogenous oxytocin on uterine smooth muscle during the second half of pregnancy?
It increases the expression of oxytocin receptors and makes the muscle more sensitive
How is oxytocin administered for labor initiation and augmentation?
Intravenous
Where is oxytocin eliminated from the body?
Kidneys & Liver
What is the half-life of oxytocin?
5 minutes
How does oxytocin act on uterine smooth muscle?
It acts through G protein-coupled receptors to contract the muscle
What is the clinical indication for oxytocin?
Control of postpartum bleeding
What does oxytocin stimulate the release of to augment uterine contraction?
Prostaglandins and leukotrienes
What is the effect of iodide therapy on a hyperplastic thyroid gland?
Decreases the size and vascularity of the gland
What is the clinical indication for using iodide therapy in cases of thyroid storm?
Management of hypermetabolic state caused by excessive release of thyroid hormones
What is a disadvantage of iodide therapy in relation to thioamide therapy?
It delays the onset of thioamide therapy
Why should chronic use of iodides be avoided in pregnancy?
Because they can cause fetal goiter
Which isotope is used for the treatment of thyrotoxicosis?
131I
What are the adverse reactions to iodine known as?
Iodism
What effect does iodide therapy have on intraglandular stores of iodine?
It increases intraglandular iodine stores
Which of the following hormones is an antagonist of the oxytocin receptor and has been approved as a treatment for preterm labor?
Atosiban
What is the active metabolite of Carbimazole?
Methimazole
What is the effect of iodide therapy on the onset of radioactive iodine therapy?
It delays the onset of radioactive iodine therapy
Which condition is due to defects in the thyroid gland itself and is the most common cause of hypothyroidism?
Primary Hypothyroidism
What is NOT a toxicity associated with Thioamides?
Grave’s Disease
Which of the following is NOT a use of 131I?
Thyroid storm
What is the most common cause of hyperthyroidism?
Grave’s Disease
What is the primary mechanism of action of agonistic GnRH analogues?
Profound suppression of LH and FSH
What is the half-life of intravenously administered GnRH analogs?
4 minutes
Which route of administration is NOT used for GnRH analogs?
Orally
What is the duration of clinical uses for GnRH analogs in cases of controlled ovarian stimulation?
A few days
What is the effect of prolonged activation of GnRH receptors by GnRH?
Desensitization of pituitary G protein coupled receptors
All are clinical indications of GnRH except?
Controlled ovarian stimulation
What is the route of administration for Nafarelin?
Nasal spray
Which hormone is responsible for the cyclical changes in estrogen and progesterone concentrations during the menstrual cycle?
Gonadotropin-releasing hormone (GnRH)
What is the primary mechanism through which ovarian suppression induced by continuous treatment with a GnRH agonist reduces estrogen and progesterone concentrations?
Inhibition of the release of GnRH from the hypothalamus
What is the temporary effect of GnRH agonists on uterine leiomyomas (fibroids) when treatment is stopped?
Gradual recurrent growth to previous size
What is the primary characteristic of uterine leiomyomata/fibroids that makes them responsive to treatment with a GnRH agonist?
Estrogen sensitivity
What is the clinical use of GnRH agonists in the treatment of uterine leiomyomas (fibroids)?
Preoperative treatment to reduce fibroid size
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?
Reduced exposure to cyclical changes in estrogen and progesterone
How does continuous treatment with a GnRH agonist impact estrogen and progesterone concentrations?
Reduces estrogen and progesterone concentrations
What is the result of treatment for 3–6 months with a GnRH agonist in terms of fibroid size?
Reduction in fibroid size
What is the role of atosiban in the treatment of preterm labor?
It acts as an oxytocin receptor antagonist
Which condition is a contraindication for the use of atosiban?
Fetal malpresentation
What is the mechanism of action of desmopressin acetate (DDAVP)?
It is a long-acting synthetic analog of vasopressin
What are the properties of vasopressin?
Antidiuretic and vasopressor
Why did the FDA decide not to approve atosiban in 1998?
Due to concerns about efficacy and safety
What is the primary role of oxytocin during the immediate postpartum period?
To augment uterine contractions and stop vaginal bleeding
In response to what physiological changes is vasopressin released by the posterior pituitary?
Rising plasma tonicity or falling blood pressure
What is the antidiuretic-to-pressor ratio of desmopressin acetate (DDAVP) compared to vasopressin?
$4000:1$
What is the role of desmopressin acetate (DDAVP) in relation to pressor activity?
$4000$ times less pressor activity than vasopressin
What is the primary role of vasopressin in the body?
Regulation of plasma tonicity and blood pressure
This quiz covers the increase in expression of oxytocin receptors in uterine smooth muscle during the second half of pregnancy, making it increasingly sensitive to the stimulant action of endogenous oxytocin in preparation for labor. It also includes information about the structure and pharmacokinetics of oxytocin.
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