Endocrinology of Pregnancy Practice Questions

Q: What is the drug of choice for the treatment of thyrotoxicosis during pregnancy?

Propylthiouracil. **Explanation:** The management of hyperthyroidism (thyrotoxicosis) in pregnancy requires a careful balance between maternal health and fetal safety. **Propylthiouracil (PTU)** is the drug of choice during the **first trimester** of pregnancy. **Why Propylthiouracil (PTU) is correct:** PTU is preferred in early pregnancy because it is more highly protein-bound than Methimazole, resulting in less placental transfer. More importantly, it is not associated with the specific congenital malformations (embryopathy) linked to other antithyroid drugs. **Why other options are incorrect:** * **Methimazole (D) & Carbimazole (A):** These are generally avoided in the first trimester because they are associated with **Methimazole Embryopathy**, which includes **Aplasia Cutis** (congenital skin defects on the scalp), choanal atresia, and esophageal atresia. However, they are often preferred in the second and third trimesters to avoid PTU-induced maternal hepatotoxicity. * **Iodine therapy (B):** Radioactive iodine ($I^{131}$) is strictly **contraindicated** in pregnancy as it crosses the placenta and can destroy the fetal thyroid gland, leading to permanent congenital hypothyroidism. **High-Yield NEET-PG Pearls:** 1. **Trimester-specific switch:** Use PTU in the 1st trimester; switch to Methimazole in the 2nd and 3rd trimesters to minimize the risk of PTU-related liver failure. 2. **Mechanism:** PTU has a dual action—it inhibits thyroid peroxidase and also inhibits the peripheral conversion of $T_4$ to $T_3$. 3. **Goal of therapy:** Aim to keep maternal Free $T_4$ levels at the **upper limit of the normal range** using the lowest possible dose to avoid fetal goiter/hypothyroidism. 4. **hCG effect:** Remember that high levels of hCG in early pregnancy can weakly stimulate the TSH receptor, leading to "Gestational Transient Thyrotoxicosis," which usually does not require antithyroid drugs.

Q: Which of the following statements regarding calcium homeostasis in pregnancy is FALSE?

Serum ionized calcium levels fall. In pregnancy, the body undergoes significant physiological adaptations to meet the fetal demand for calcium (approximately 30g), primarily through enhanced intestinal absorption rather than maternal bone resorption. **Explanation of the Correct Answer (B):** The hallmark of calcium homeostasis in pregnancy is that **serum ionized calcium levels remain constant (unchanged).** Ionized calcium is the physiologically active fraction regulated tightly by the parathyroid hormone (PTH). While total serum calcium levels fall due to hemodilution and decreased albumin, the free, ionized portion does not change. Therefore, the statement that ionized calcium levels "fall" is **false**. **Analysis of Incorrect Options:** * **Option A (True statement):** Serum **non-ionized (bound) calcium** levels fall. This occurs because total serum albumin levels decrease due to plasma volume expansion (hemodilution). Since a large portion of calcium is bound to albumin, the total (non-ionized) calcium concentration decreases. * **Option C (True statement):** Intestinal absorption of calcium **doubles** starting from the first trimester. This is the primary mechanism to meet fetal needs and protect maternal bone mineral density. * **Option D (True statement):** Levels of **1,25-dihydroxyvitamin D (Calcitriol)** increase significantly. This is driven by increased PTHrP (from the placenta/breasts) and direct stimulation of 1-alpha-hydroxylase in the maternal kidneys and placenta. **High-Yield NEET-PG Pearls:** * **Total Calcium:** Decreases (due to low albumin). * **Ionized Calcium:** Remains **Unchanged**. * **24-hour Urinary Calcium:** Increases (absorptive hypercalciuria); hence, pregnancy is a pro-lithogenic state for kidney stones. * **PTH:** May slightly decrease in the first trimester but generally remains in the normal range or increases slightly later in pregnancy.

Q: Complications of diabetes in pregnancy include all of the following except?

Hyperglycemia in the newborn. **Explanation:** The correct answer is **C. Hyperglycemia in the newborn**. In reality, infants of diabetic mothers (IDMs) are at high risk for **neonatal hypoglycemia**, not hyperglycemia. **Pathophysiology (Pedersen Hypothesis):** Maternal hyperglycemia leads to fetal hyperglycemia because glucose crosses the placenta via facilitated diffusion. However, maternal insulin does not cross the placenta. The fetal pancreas responds to high glucose levels by producing excess insulin (**fetal hyperinsulinemia**). After birth, the glucose supply from the mother is abruptly cut off, but the neonate’s hyperinsulinemic state persists, causing rapid glucose uptake and profound hypoglycemia. **Analysis of Incorrect Options:** * **Macrosomia (A):** Fetal hyperinsulinemia acts as a growth promoter, leading to excessive fat deposition and organomegaly (birth weight >4000g or >4500g). * **Shoulder Dystocia (B):** Macrosomic infants have disproportionate fat deposition around the shoulders and trunk, significantly increasing the risk of birth trauma and shoulder dystocia during vaginal delivery. * **Intrauterine Growth Restriction (D):** While GDM usually causes macrosomia, **Pregestational Diabetes** (Type 1 or 2) with long-standing vascular complications (White’s Class D, F, R) can lead to placental insufficiency, resulting in IUGR. **High-Yield NEET-PG Pearls:** * **Most common cardiac anomaly:** Ventricular Septal Defect (VSD). * **Most specific cardiac anomaly:** Transposition of the Great Arteries (TGA). * **Most specific malformation overall:** Caudal Regression Syndrome (Sacral Agenesis). * **Neonatal Metabolic Triad:** Hypoglycemia, Hypocalcemia, and Hypomagnesemia. * **Other complications:** Polycythemia (due to fetal hypoxia/erythropoietin) and Hyperbilirubinemia.

Q: At what value of a one-hour glucose challenge test would you recommend a standard glucose tolerance test?

140 mg/dL. This question pertains to the screening protocol for **Gestational Diabetes Mellitus (GDM)** using the two-step approach (Carpenter-Coustan criteria). ### **Explanation** The screening process typically begins between **24 and 28 weeks of gestation** with a **50g Glucose Challenge Test (GCT)** [1]. This is a non-fasting test where plasma glucose is measured one hour after glucose ingestion [1]. * **The Threshold:** A value of **≥140 mg/dL (7.8 mmol/L)** is the standard cutoff used to identify women at high risk. If the GCT result meets or exceeds this value, the test is considered "positive" (abnormal), and the patient must proceed to the diagnostic **100g, 3-hour Oral Glucose Tolerance Test (OGTT)**. * *Note:* Some clinicians use a lower cutoff of 130 mg/dL to increase sensitivity, but 140 mg/dL remains the most widely tested standard in medical examinations. ### **Analysis of Incorrect Options** * **A. 120 mg/dL:** This value is too low and falls within the normal postprandial range for many individuals; using this would result in an excessive number of false positives. * **C. 150 mg/dL & D. 160 mg/dL:** While these values are certainly abnormal, they are too high to serve as a primary screening cutoff [2]. Using these would miss a significant percentage of women with GDM (low sensitivity). ### **High-Yield Clinical Pearls for NEET-PG** * **DIPSI Guidelines:** In India, the DIPSI (Diabetes in Pregnancy Study Group India) recommends a **single-step** procedure: 75g glucose load regardless of fasting status. A 2-hour value **≥140 mg/dL** is diagnostic of GDM. * **O'Sullivan's Criteria:** If the 1-hour GCT is **>200 mg/dL**, GDM is diagnosed directly without needing a follow-up OGTT [2]. * **Risk Factors:** Screening should be done at the **first prenatal visit** if the patient is obese, has a history of GDM, or has a strong family history of Type 2 Diabetes.

Q: Which of the following is contraindicated during pregnancy?

Radioiodine. **Explanation:** **Radioiodine (I-131)** is strictly contraindicated during pregnancy because it readily crosses the placenta. After the 10th–12th week of gestation, the fetal thyroid gland begins to concentrate iodine. Exposure to therapeutic doses of I-131 can lead to irreversible **fetal thyroid ablation**, resulting in congenital hypothyroidism (cretinism) and potential neurodevelopmental delays. Additionally, there is a theoretical risk of fetal malignancy due to radiation exposure. **Analysis of Incorrect Options:** * **Thiouracil (Antithyroid Drugs):** Propylthiouracil (PTU) and Methimazole are the mainstays of treatment for hyperthyroidism in pregnancy. While they cross the placenta, they are used at the lowest effective dose to maintain maternal euthyroidism. PTU is preferred in the first trimester (due to Methimazole-associated embryopathy), while Methimazole is often used in the second and third trimesters. * **Surgery:** Subtotal thyroidectomy is not contraindicated but is reserved for specific cases (e.g., drug intolerance or suspected malignancy). If required, it is ideally performed during the **second trimester** to minimize the risk of miscarriage (1st trimester) or preterm labor (3rd trimester). **High-Yield Clinical Pearls for NEET-PG:** * **Pregnancy Test:** Always perform a pregnancy test before administering radioiodine to any woman of reproductive age. * **Breastfeeding:** Radioiodine is also contraindicated during breastfeeding as it is secreted in breast milk. * **Thyroid Physiology:** Total T3 and T4 levels increase during pregnancy due to increased Thyroid Binding Globulin (TBG), but **Free T4** remains the most reliable marker for diagnosis. * **hCG Effect:** High levels of hCG (which shares an alpha subunit with TSH) can weakly stimulate the TSH receptor, leading to transient gestational thyrotoxicosis.

Q: Which one of the following is not associated with diabetes in pregnancy?

Advanced placental grading. **Explanation:** In diabetes complicating pregnancy, the placenta typically undergoes **delayed maturation** rather than advanced grading. **1. Why "Advanced Placental Grading" is the correct answer:** Advanced placental maturation (Grade III) is usually associated with conditions causing placental insufficiency and ischemia, such as **Pregnancy-Induced Hypertension (PIH)** or post-dated pregnancy. In contrast, maternal diabetes leads to a large, edematous, and immature placenta. Histologically, there is a persistence of cytotrophoblastic cells and delayed villous maturation, which can impair oxygen transfer despite the increased placental size. **2. Analysis of Incorrect Options:** * **Sacral Agenesis:** This is the **most specific** congenital anomaly associated with maternal diabetes (though not the most common, which is VSD). It is part of Caudal Regression Syndrome. * **Baby weight > 3.5 kg:** Maternal hyperglycemia leads to fetal hyperinsulinemia. Insulin acts as a growth hormone, causing fetal macrosomia (typically defined as >4 kg or >4.5 kg, but >3.5 kg is a common clinical threshold for concern). * **Hydramnios:** Polyhydramnios occurs in approximately 25% of diabetic pregnancies. It is primarily caused by **fetal osmotic diuresis** resulting from fetal hyperglycemia, leading to increased amniotic fluid production. **Clinical Pearls for NEET-PG:** * **Most common anomaly:** Ventricular Septal Defect (VSD). * **Most specific anomaly:** Sacral agenesis/Caudal regression syndrome. * **HbA1c Goal:** Ideally <6.0% pre-conception to minimize the risk of anomalies. * **Neonatal Complications:** Hypoglycemia, Hypocalcemia, Hyperbilirubinemia, and Polycythemia. (Note: Hyperglycemia is *not* a neonatal complication; the baby becomes hypoglycemic once the maternal glucose supply is cut off).

Q: What is true regarding maternal plasma osmolality during pregnancy?

Maternal plasma osmolality decreases early in pregnancy.. ### Explanation **1. Why Option A is Correct:** During pregnancy, there is a significant resetting of the **osmostat** (the hypothalamic threshold for thirst and ADH release). Starting as early as the 5th week of gestation, the threshold for arginine vasopressin (AVP/ADH) release and the sensation of thirst both decrease. This leads to increased water retention. Consequently, maternal plasma osmolality **decreases by approximately 10 mOsm/kg** below non-pregnant levels. This physiological hemodilution is a hallmark of normal pregnancy. **2. Why the Other Options are Incorrect:** * **Option B & C:** These are incorrect because osmolality does not increase or remain static; it undergoes a definitive decline early in the first trimester and remains low until delivery. * **Option D:** While sodium is the primary determinant of osmolality in non-pregnant states, the drop in osmolality during pregnancy is primarily driven by **water retention** exceeding the rate of sodium retention. Although total body sodium increases (by ~900 mEq), the relative expansion of plasma volume leads to a state of mild **dilutional hyponatremia** (sodium levels typically drop by 3–5 mEq/L). **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **The "10 Unit" Rule:** Remember that plasma osmolality drops by roughly **10 mOsm/kg** (from ~285 to ~275 mOsm/kg). * **Hormonal Influence:** The resetting of the osmostat is largely attributed to increased levels of **hCG** and **relaxin**. * **Plasma Volume:** Increases by 40–50%, peaking at 32–34 weeks. Since RBC mass increases only by 20–30%, this results in **physiological anemia**. * **Key Takeaway:** If a question asks about sodium levels in pregnancy, they are **decreased** (dilutional), even though total body sodium is **increased**.

Q: What is the least likely complication in a pregnant mother with hypothyroidism?

Polyhydramnios. **Explanation:** Hypothyroidism in pregnancy is characterized by a deficiency of thyroid hormones, which are essential for maintaining early pregnancy and ensuring normal fetomaternal hemodynamics. **Why Polyhydramnios is the Correct Answer:** Polyhydramnios (excess amniotic fluid) is **not** typically associated with maternal hypothyroidism. In fact, severe hypothyroidism is more likely to be associated with **Oligohydramnios** (decreased amniotic fluid), often secondary to placental insufficiency or fetal growth restriction (FGR). Polyhydramnios is more commonly linked to maternal diabetes, fetal structural anomalies (like esophageal atresia), or fetal hydrops. **Analysis of Incorrect Options:** * **Recurrent Abortions:** Thyroid hormones are crucial for the development of the corpus luteum and early placentation. Deficiency leads to an inadequate luteal phase and early pregnancy loss. * **Preterm Labor:** Hypothyroidism increases the risk of placental abruption and oxidative stress, both of which are significant triggers for spontaneous preterm birth. * **Hypertension:** There is a strong correlation between hypothyroidism and **Gestational Hypertension/Pre-eclampsia**. The lack of thyroxine leads to increased peripheral vascular resistance and altered cardiovascular reactivity. **High-Yield NEET-PG Pearls:** * **Drug of Choice:** Levothyroxine is the mainstay of treatment. * **Dose Adjustment:** Requirements increase by **30–50%** during pregnancy, starting as early as the 4th–6th week. * **Target TSH:** The goal is to keep TSH <2.5 mIU/L in the first trimester and <3.0 mIU/L in the subsequent trimesters. * **Most common cause:** Globally, iodine deficiency; in iodine-sufficient areas, **Hashimoto’s Thyroiditis**.

Question 1

What is the drug of choice for the treatment of thyrotoxicosis during pregnancy?

Accepted Answer

Propylthiouracil

Answer

Carbimazole

Answer

Iodine therapy

Answer

Metimazole

Question 2

Which of the following statements regarding calcium homeostasis in pregnancy is FALSE?

Accepted Answer

Serum ionized calcium levels fall

Answer

Serum non-ionized calcium levels fall

Answer

Intestinal absorption of calcium is increased

Answer

Levels of 1,25-dihydroxyvitamin D are increased

Question 3

Complications of diabetes in pregnancy include all of the following except?

Accepted Answer

Hyperglycemia in the newborn

Answer

Macrosomia

Answer

Shoulder dystocia

Answer

Intrauterine growth restriction (IUGR)

Question 4

At what value of a one-hour glucose challenge test would you recommend a standard glucose tolerance test?

Accepted Answer

140 mg/dL

Answer

120 mg/dL

Answer

150 mg/dL

Answer

160 mg/dL

Question 5

Which of the following statements are true regarding human chorionic gonadotropin (hCG)?

Accepted Answer

It causes involution of the corpus luteum.

Answer

The alpha subunit is identical to that of LH, FSH, and TSH.

Answer

It doubles in level every 7-10 days.

Answer

The maximum level is seen at 60-70 days of gestation.

Question 6

Which of the following is contraindicated during pregnancy?

Accepted Answer

Radioiodine

Answer

Thiouracil

Answer

Surgery

Answer

None of the above

Question 7

Which one of the following is not associated with diabetes in pregnancy?

Accepted Answer

Advanced placental grading

Answer

Sacral agenesis of the fetus

Answer

Baby weight > 3.5 kg

Answer

Hydramnios

Question 8

Which of the following is not a risk factor for a woman to develop gestational diabetes?

Accepted Answer

Working mother

Answer

Previous macrosomic baby

Answer

Previous history of gestational diabetes

Answer

Both parents have diabetes

Question 9

What is true regarding maternal plasma osmolality during pregnancy?

Accepted Answer

Maternal plasma osmolality decreases early in pregnancy.

Answer

Maternal plasma osmolality increases throughout pregnancy.

Answer

Maternal plasma osmolality does not change during pregnancy.

Answer

Maternal plasma osmolality is affected most by increases in sodium.

Question 10

What is the least likely complication in a pregnant mother with hypothyroidism?

Accepted Answer

Polyhydramnios

Answer

Recurrent abortions

Answer

Preterm labor

Answer

Hypertension

Endocrinology of Pregnancy — MCQs

Endocrinology of Pregnancy — MCQs

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