A 37-year-old woman, gravida 2 para 1, at 30 weeks gestation comes to the office to discuss her recent laboratory work. At her last visit at 28 weeks gestation, the patient drank a solution containing 50 g of glucose, and her serum glucose was abnormally elevated an hour later. Today, she is scheduled to undergo a confirmatory 3-hour glucose test. Her pregnancy has been uncomplicated, and the patient has no chronic medical conditions. She is taking a daily prenatal vitamin. Vital signs are normal. Physical examination shows a uterine size consistent with gestational age. Fetal heart rate is 140/min. Which of the following hormones is most likely contributing to this patient's abnormal laboratory findings?

Question

A 37-year-old woman, gravida 2 para 1, at 30 weeks gestation comes to the office to discuss her recent laboratory work.  At her last visit at 28 weeks gestation, the patient drank a solution containing 50 g of glucose, and her serum glucose was abnormally elevated an hour later.  Today, she is scheduled to undergo a confirmatory 3-hour glucose test.  Her pregnancy has been uncomplicated, and the patient has no chronic medical conditions.  She is taking a daily prenatal vitamin.  Vital signs are normal.  Physical examination shows a uterine size consistent with gestational age.  Fetal heart rate is 140/min.  Which of the following hormones is most likely contributing to this patient's abnormal laboratory findings?

Quizplus · Accepted Answer

11ec160b_3cd7_f514_9249_e9fc1911d94f_MD0001_00 During pregnancy, a physiologic increase in maternal insulin resistance occurs during the second and third trimesters, largely due to human placental lactogen (hPL), a peptide hormone secreted by the syncytiotrophoblast. hPL establishes a glucose-sparing effect that results in: hPL also stimulates maternal pancreatic beta-cell proliferation to increase insulin production to counteract the rising resistance. This physiologic process becomes pathologic (ie, gestational diabetes mellitus) when the pancreatic function is not sufficient to overcome the pregnancy-related increase in insulin resistance. Average levels of hPL rise with increasing gestational age, reflecting the increasing energy requirements of the growing fetus. Therefore, screening for gestational diabetes is performed in the late second or early third trimester (when plasma levels of hPL are peaking) to ensure screening accuracy. (Choice A) Growth hormone, released from the pituitary gland, causes an increase in insulin resistance and fat breakdown; however, growth hormone secretion does not increase during pregnancy. (Choice B) In early pregnancy, the placental syncytiotrophoblast secretes human chorionic gonadotropin, a peptide hormone, which stimulates the corpus luteum to produce progesterone, a steroid hormone. Progesterone is necessary to maintain the secretory endometrium, allowing the pregnancy to persist through term. (Choice D) Prolactin is a peptide hormone secreted by lactotroph cells in the anterior pituitary. It stimulates ductal and alveolar growth in breast tissue and is responsible for milk production and lactation in postpartum women. (Choice E) Pregnancy increases the levels of thyroid-binding globulin, leading to increased total circulating T₃ and T₄. However, free thyroid hormone levels remain essentially normal. Educational objective: Human placental lactogen creates a fetal glucose-sparing effect by increasing maternal insulin resistance during the second and third trimesters, leading to a rise in serum glucose that helps provide adequate nutrition to the growing fetus. Gestational diabetes occurs when the compensatory rise in maternal insulin secretion is inadequate to prevent serum glucose levels from reaching excessively high levels.

A 37-Year-Old Woman, Gravida 2 Para 1, at 30 Weeks