Thyroid Disorders in Pregnancy — MCQs
The choice of drug for hyperthyroidism in the first trimester of pregnancy is?
Thyroxine binding globulin (TBG) is increased in:
Preoperative medication of thyrotoxicosis are all except?
A pregnant woman is diagnosed with Graves' disease. The most appropriate therapy for her would be:
Which antithyroid drug is safer during the first trimester of pregnancy?
To assess thyroid profile of a newborn, which of the following is mandatory?
Hypothyroidism in pregnancy is most likely associated with which of the following?
Which of the following endocrinological conditions may be associated with hydatidiform mole: 46,XX?
Which of the following statements about cholestasis of pregnancy is false?
Blood volume increases during pregnancy above nonpregnant level at 30-34 weeks by:
Thyroid Disorders in Pregnancy Indian Medical PG Practice Questions and MCQs
Question 1: The choice of drug for hyperthyroidism in the first trimester of pregnancy is?
- A. Methimazole
- B. Carbimazole
- C. Perchlorate
- D. Propylthiouracil (Correct Answer)
Explanation: ***Propylthiouracil*** - **Propylthiouracil (PTU)** is the preferred treatment for hyperthyroidism during the **first trimester of pregnancy** due to a lower risk of teratogenicity compared to methimazole [1]. [2] - While PTU can cause **liver toxicity**, the risk of birth defects with methimazole in the first trimester is generally considered greater [2]. *Methimazole* - **Methimazole** is generally avoided in the first trimester because it is associated with a higher risk of **congenital anomalies**, specifically **aplasia cutis** and **esophageal atresia**. - It becomes the preferred choice in the **second and third trimesters**, as its side effect profile for the mother is often more favorable [1]. *Carbimazole* - **Carbimazole** is a prodrug that is converted to **methimazole** in the body, and therefore shares the same teratogenic risks as methimazole in the first trimester [2]. - It is also generally avoided during early pregnancy due to the risk of **fetal malformations**. *Perchlorate* - **Perchlorate** can be used to treat hyperthyroidism, but it is not typically a first-line drug, especially in pregnancy. - Its mechanism involves blocking **iodide uptake** into the thyroid gland, but it is associated with potential side effects and other treatment options are generally preferred due to their better-established safety profiles in pregnancy.
Question 2: Thyroxine binding globulin (TBG) is increased in:
- A. Pregnancy (Correct Answer)
- B. Cancer chemotherapy
- C. Nephrotic syndrome
- D. Glucocorticoid therapy
Explanation: ***Pregnancy*** - Estrogen levels are elevated during **pregnancy**, which leads to an increase in the synthesis of **TBG** by the liver. - Increased TBG binds more thyroid hormone, reducing free thyroid hormone levels, which then stimulates the thyroid gland to produce more. *Cancer chemotherapy* - Many **chemotherapeutic agents** can damage the liver or interfere with protein synthesis, potentially leading to a *decrease* in TBG and other plasma proteins. - Chemotherapy can also induce **hypothyroidism** directly or indirectly, which may alter thyroid hormone binding. *Nephrotic syndrome* - **Nephrotic syndrome** is characterized by significant proteinuria, where plasma proteins, including **TBG**, are lost through the kidneys in the urine. - This leads to a *decrease* in serum TBG levels, which can affect total thyroid hormone measurements but typically does not cause overt thyroid dysfunction due to compensatory mechanisms. *Glucocorticoid therapy* - **Glucocorticoids** (e.g., prednisone, dexamethasone) are known to *decrease* the hepatic synthesis of **TBG**. - This reduction in TBG can lead to lower total thyroid hormone levels without necessarily indicating thyroid gland dysfunction, as free thyroid hormone levels often remain normal.
Question 3: Preoperative medication of thyrotoxicosis are all except?
- A. Carbimazole
- B. PTU
- C. Propranolol
- D. Levothyroxine (Correct Answer)
Explanation: Levothyroxine - Levothyroxine is a synthetic thyroid hormone used to treat hypothyroidism, meaning it increases thyroid hormone levels, which would worsen thyrotoxicosis [1]. - Its administration would be contraindicated in a patient with thyrotoxicosis, as the goal is to reduce thyroid hormone levels preoperatively. Carbimazole - Carbimazole is a thionamide drug that inhibits the synthesis of thyroid hormones, making it a critical medication for treating hyperthyroidism and preparing patients for surgery [1]. - It reduces the amount of thyroid hormone produced by the thyroid gland, thus mitigating the risks associated with thyrotoxicosis during surgery. PTU - Propylthiouracil (PTU), like carbimazole, is a thionamide that blocks thyroid hormone synthesis and also inhibits the conversion of T4 to T3 [1]. - It is used in the preoperative management of thyrotoxicosis to achieve a euthyroid state and prevent a thyroid storm. Propranolol - Propranolol is a beta-blocker used to manage the symptoms of thyrotoxicosis, particularly the cardiovascular effects such as tachycardia, palpitations, and tremors [1]. - While it does not affect thyroid hormone levels directly, it helps control symptoms and stabilize the patient preoperatively, making them a safer candidate for surgery [1].
Question 4: A pregnant woman is diagnosed with Graves' disease. The most appropriate therapy for her would be:
- A. Radioiodine therapy
- B. Total thyroidectomy
- C. Carbimazole parenteral
- D. Propylthiouracil oral (Correct Answer)
Explanation: ***Propylthiouracil oral*** - **Propylthiouracil (PTU)** is the preferred antithyroid drug during the **first trimester** of pregnancy due to a lower risk of teratogenicity compared to methimazole/carbimazole [1]. - It works by inhibiting both the synthesis of thyroid hormones and the peripheral conversion of **T4 to T3**. *Radioiodine therapy* - **Radioactive iodine** is absolutely contraindicated in pregnancy as it can cross the placenta and cause **fetal hypothyroidism or athyreosis**. - It leads to permanent destruction of the thyroid gland and is not suitable for a temporary condition in a pregnant woman. *Total thyroidectomy* - While thyroidectomy can be considered for Graves' disease in pregnancy, it is generally reserved for cases where antithyroid drugs are not tolerated or ineffective, or for very large goiters causing compressive symptoms. - It carries risks associated with **surgery and anesthesia** during pregnancy, and requires **lifelong thyroid hormone replacement**. *Carbimazole parenteral* - **Carbimazole** (which is metabolized to methimazole) is generally avoided in the **first trimester** due to an increased risk of teratogenicity, particularly **aplasia cutis**, omphalocele, and choanal atresia [1]. - While it can be used in the second and third trimesters, **PTU is preferred in the first trimester**, and carbimazole is not typically administered parenterally.
Question 5: Which antithyroid drug is safer during the first trimester of pregnancy?
- A. Radioactive iodine
- B. Carbimazole
- C. Propylthiouracil (Correct Answer)
- D. Methimazole
- E. Propranolol
Explanation: ***Propylthiouracil*** - **Propylthiouracil (PTU)** is the preferred drug for treating hyperthyroidism in the **first trimester of pregnancy** due to a lower risk of teratogenic effects compared to methimazole or carbimazole. - While PTU carries a risk of hepatic toxicity, it is generally favored during early pregnancy to avoid the established teratogenic risks of other thionamides. *Radioactive iodine* - **Radioactive iodine (RAI)** is absolutely contraindicated in pregnancy as it crosses the placenta and can cause permanent **fetal hypothyroidism** or **agenesis of the fetal thyroid gland**. - Its use can lead to the destruction of the fetal thyroid, which is unacceptable given the availability of safer alternatives. *Carbimazole* - **Carbimazole** is converted to methimazole in the body and is associated with a higher risk of **fetal embryopathy** during the first trimester, including aplasia cutis, choanal atresia, and esophageal atresia. - It should generally be avoided in the first trimester if possible, switching to PTU instead. *Methimazole* - **Methimazole** is structurally similar to carbimazole and also carries a significant risk of **teratogenic effects** such as **aplasia cutis**, omphalocele, and choanal atresia when used in the first trimester. - It is often reserved for the second and third trimesters if a thionamide is required, or for patients who cannot tolerate PTU, but ideally avoided in early pregnancy. *Propranolol* - **Propranolol** is a beta-blocker used for symptomatic management of hyperthyroidism (controlling tachycardia, tremor, anxiety) but is not an antithyroid drug and does not treat the underlying hyperthyroidism. - While generally safe in pregnancy, it only provides adjunctive therapy and cannot replace definitive antithyroid treatment.
Question 6: To assess thyroid profile of a newborn, which of the following is mandatory?
- A. Measure T3 only
- B. Measure TSH only
- C. Measure both TSH and T4 (Correct Answer)
- D. Measure T4 only
Explanation: ***Measure both TSH and T4*** - **Newborn screening** for congenital hypothyroidism typically involves measuring both **TSH** (thyroid-stimulating hormone) and **T4** (thyroxine). - Elevated TSH levels indicate **primary hypothyroidism**, where the thyroid gland is underactive, while low T4 levels confirm the reduced thyroid hormone production. *Measure T3 only* - **T3 (triiodothyronine)** is generally not the primary screening test for congenital hypothyroidism in newborns. - While T3 is an active form of thyroid hormone, its levels can be influenced by various factors and are less reliable than TSH and T4 for initial screening. *Measure TSH only* - Measuring only **TSH** can detect primary hypothyroidism, but it doesn't provide a complete picture of thyroid function. - In cases of **central (secondary or tertiary) hypothyroidism**, TSH levels might be normal or low, while T4 levels are reduced, which would be missed if only TSH were measured. *Measure T4 only* - Measuring only **T4** can help identify low thyroid hormone levels, but it doesn't differentiate between primary and central hypothyroidism. - To properly assess the cause of low T4, **TSH levels** are crucial to determine if the problem lies within the thyroid gland itself or higher up in the pituitary/hypothalamic axis.
Question 7: Hypothyroidism in pregnancy is most likely associated with which of the following?
- A. Recurrent abortions
- B. Preeclampsia (Correct Answer)
- C. Preterm labour
- D. Polyhydramnios
Explanation: ***Preeclampsia*** - **Hypothyroidism** in pregnancy is strongly linked to an increased risk of **preeclampsia**, a serious condition characterized by **hypertension and proteinuria** after 20 weeks of gestation. - The exact mechanism is not fully understood, but thyroid hormones play a crucial role in maintaining **vascular tone and endothelial function**, which are disrupted in preeclampsia. - Studies show that both **overt and subclinical hypothyroidism** increase the risk of preeclampsia, making this the **most likely association** among the given options. *Recurrent abortions* - While uncontrolled **hypothyroidism** can increase the risk of **first-trimester miscarriage**, it is not typically cited as the most likely association for **recurrent abortions** compared to preeclampsia. - Other causes like **chromosomal abnormalities, uterine anomalies, or antiphospholipid syndrome** are more common for recurrent pregnancy loss. - Early detection and treatment with **levothyroxine** can reduce miscarriage risk. *Polyhydramnios* - **Polyhydramnios** (excess amniotic fluid) is more often associated with conditions like **gestational diabetes**, fetal anomalies (e.g., GI obstruction, neural tube defects), or multiple gestation. - **Hypothyroidism** is not a primary risk factor for **polyhydramnios**; fetal thyroid dysfunction (e.g., fetal hyperthyroidism due to maternal Graves' disease) is more relevant to amniotic fluid disorders. - Maternal hypothyroidism does not typically affect amniotic fluid volume. *Preterm labour* - Poorly controlled **hypothyroidism** can increase the risk of **preterm birth**, but **preeclampsia** is generally considered a more distinct and stronger association. - Other common causes of **preterm labor** include infections, uterine abnormalities, cervical insufficiency, and multiple gestations. - Adequate thyroid hormone replacement reduces obstetric complications including preterm delivery.
Question 8: Which of the following endocrinological conditions may be associated with hydatidiform mole: 46,XX?
- A. Hypothyroidism
- B. Diabetes
- C. Hyperprolactinemia
- D. Hyperthyroidism (Correct Answer)
Explanation: ***Hyperthyroidism*** - A **complete hydatidiform mole** produces very high levels of **human chorionic gonadotropin (hCG)**, which has a structural similarity to **thyroid-stimulating hormone (TSH)**. - This **hCG** can bind to **TSH receptors** on the thyroid gland, stimulating **thyroid hormone production** and leading to **hyperthyroidism**. *Hypothyroidism* - **Hypothyroidism** is characterized by **low thyroid hormone levels** and is not directly induced by the hormonal changes associated with a hydatidiform mole. - While pregnancy can sometimes unmask or worsen hypothyroidism, it is not a direct endocrinological consequence of a molar pregnancy. *Diabetes* - **Diabetes mellitus** is a metabolic disorder characterized by **high blood glucose**, commonly associated with insulin resistance or deficiency. - There is no direct endocrinological link between **hydatidiform mole** and the development of diabetes. *Hyperprolactinemia* - **Hyperprolactinemia** is characterized by **elevated prolactin levels**, often leading to menstrual irregularities and galactorrhea. - While pregnancy itself causes an increase in prolactin, a hydatidiform mole does not specifically induce pathological **hyperprolactinemia**.
Question 9: Which of the following statements about cholestasis of pregnancy is false?
- A. Bilirubin level >2mg%
- B. Most common cause of jaundice in pregnancy (Correct Answer)
- C. Oestrogen is involved
- D. Manifestations usually appear in last trimester
Explanation: ***Most common cause of jaundice in pregnancy*** - This statement is **FALSE** - while **intrahepatic cholestasis of pregnancy (ICP)** is the most common **pregnancy-specific** cause of jaundice, it is NOT the most common cause of jaundice overall in pregnancy. - **Viral hepatitis** (especially hepatitis A, B, and E) remains the **most common cause of jaundice in pregnancy** worldwide, accounting for approximately 40-50% of cases. - ICP accounts for about 20-25% of jaundice cases in pregnancy, making it the leading obstetric-specific cause but not the overall leading cause. *Bilirubin level >2mg%* - In ICP, **bilirubin levels** are typically **normal or only mildly elevated** (usually <4 mg/dL, often <2 mg/dL). - However, bilirubin **can exceed 2 mg/dL** in some cases of ICP, particularly in more severe presentations. - The primary diagnostic marker is elevated **serum bile acids** (>10 μmol/L), not bilirubin. *Oestrogen is involved* - **TRUE** - Elevated **estrogen and progesterone levels** during pregnancy play a key role in ICP pathophysiology. - These hormones affect **hepatic bile salt transporters** (particularly BSEP and MDR3), leading to impaired bile secretion in genetically susceptible individuals. *Manifestations usually appear in last trimester* - **TRUE** - ICP typically presents in the **third trimester** (usually after 28 weeks), with **pruritus** as the predominant symptom. - Symptoms resolve within days to weeks after delivery, correlating with declining hormone levels.
Question 10: Blood volume increases during pregnancy above nonpregnant level at 30-34 weeks by:
- A. Blood volume does not increase at all
- B. by 25-30 per cent
- C. by 40-50 per cent (Correct Answer)
- D. by 10-20 per cent
Explanation: ***by 40-50 per cent*** - During pregnancy, **blood volume significantly increases**, primarily due to hormonal changes, to support the growing fetus and uteroplacental unit, with the peak increase typically occurring around the third trimester. - This expansion involves both **plasma volume (greater increase)** and **red blood cell mass**, leading to a state of physiologic hemodilution. *Blood volume does not increase at all* - This statement is incorrect as a substantial **increase in blood volume is a hallmark of normal pregnancy physiology** to meet increased metabolic demands. - Failure of blood volume to increase would imply a pathologic state, potentially compromising both maternal and fetal well-being. *by 25-30 per cent* - While a significant increase, **25-30% is generally an underestimation** of the full extent of blood volume expansion that occurs in a healthy pregnancy. - The total increase often reaches higher values, particularly when considering the combined rise in plasma and red blood cells. *by 10-20 per cent* - An increase of **10-20% is considerably less** than what is typically observed during a normal pregnancy. - This level of increase would likely be insufficient to adequately support the physiological demands of the mother and fetus.
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