Endocrine Pharmacology Practice Questions

Q: The drug of choice for hyperthyroidism during the 2nd trimester of pregnancy is:

Carbimazole. ***Carbimazole*** - **Carbimazole** is converted to **methimazole** in the body, which is generally preferred in the second and third trimesters due to a lower risk of serious liver toxicity compared to propylthiouracil. - While propylthiouracil is preferred in the first trimester, **methimazole/carbimazole** is considered safer in later trimesters after the period of major organogenesis. *Propylthiouracil* - **Propylthiouracil (PTU)** is the drug of choice for hyperthyroidism during the **first trimester** of pregnancy because of a lower risk of teratogenicity compared to methimazole/carbimazole. - However, **PTU** carries a risk of **hepatic toxicity** in the mother, making carbimazole/methimazole preferable in the second and third trimesters once the initial teratogenic risk largely passes. *Sodium iodide* - **Sodium iodide** is generally **contraindicated** in pregnancy for routine treatment of hyperthyroidism as it can cross the placenta and potentially cause **fetal goiter** and **hypothyroidism**. - Its use is typically limited to **thyroid storm** or preparation for thyroidectomy when other options are not suitable. *Radioactive iodine* - **Radioactive iodine (I-131)** is **absolutely contraindicated** during any trimester of pregnancy and lactation. - It rapidly crosses the placenta and can **ablate the fetal thyroid gland**, leading to permanent fetal hypothyroidism.

Q: Which of the following is the synthetic form of Triiodothyronine (T3)?

Liothyronine sodium. ***Liothyronine sodium*** - This is the **synthetic form of Triiodothyronine (T3)**, the more potent and active form of thyroid hormone. - It has a **rapid onset of action** (within a few hours) and shorter half-life compared to T4. - Used in cases where direct T3 replacement is needed, such as in **myxedema coma** or for suppression testing. *Levothyroxine sodium* - This is the synthetic form of **Thyroxine (T4)**, which is then converted to T3 in peripheral tissues. - It is the **most common preparation** for treating hypothyroidism due to its longer half-life (7 days) and stable serum levels. *Liotrix* - Liotrix is a **combination preparation of synthetic T4 and synthetic T3**, typically in a 4:1 ratio. - It aims to mimic the natural physiological ratio; however, its use is **less common** than levothyroxine monotherapy. *Propylthiouracil* - This is an **antithyroid drug** used to treat hyperthyroidism, not a thyroid hormone replacement. - It works by inhibiting thyroid peroxidase and peripheral conversion of T4 to T3.

Q: Which of the following is a testosterone inhibitor?

Spironolactone. ***Spironolactone*** - Spironolactone is an **androgen receptor antagonist** and also inhibits **testosterone synthesis** by blocking 17α-hydroxylase and 17,20-lyase enzymes. - This dual action reduces the effects and production of testosterone, making it useful in conditions like **hirsutism** and **polycystic ovary syndrome (PCOS)**. *Clomiphene* - Clomiphene is a **selective estrogen receptor modulator (SERM)** that acts as an antagonist in the hypothalamus, thereby increasing the pulsatile release of GnRH. - This leads to increased FSH and LH secretion, stimulating **ovulation in women** and **testosterone production in men**, rather than inhibiting testosterone. *Bremelanotide* - Bremelanotide is a **melanocortin receptor agonist** that acts on the central nervous system to increase sexual desire. - It is used to treat **hypoactive sexual desire disorder (HSDD)** in premenopausal women and has no direct effect on testosterone levels or action. *Sildenafil* - Sildenafil is a **phosphodiesterase-5 (PDE5) inhibitor** that increases blood flow to the penis by enhancing the effects of nitric oxide, leading to an erection. - It is primarily used to treat **erectile dysfunction** and does not directly inhibit testosterone.

Q: Which of the following drugs does not cause hyperprolactinemia?

Bromocriptine. ***Bromocriptine*** - Bromocriptine is a **dopamine agonist** that directly activates dopamine D2 receptors in the pituitary gland, leading to a **decrease in prolactin secretion** [1], [3]. - It is commonly used in the treatment of **hyperprolactinemia** and prolactinomas, not a cause of it [2]. *Haloperidol* - Haloperidol is a **first-generation antipsychotic** drug that blocks dopamine D2 receptors in the pituitary. - This blockade leads to a **disinhibition of prolactin secretion**, resulting in hyperprolactinemia. *Reserpine* - Reserpine depletes **monoamines**, including dopamine, from presynaptic nerve terminals in the brain. - The resulting **reduction in dopamine availability** at the pituitary level leads to increased prolactin secretion and hyperprolactinemia. *Chlorpromazine* - Chlorpromazine is a **phenothiazine antipsychotic** that significantly blocks dopamine D2 receptors. - This **dopamine antagonism** prevents the tonic inhibition of prolactin release, thereby causing hyperprolactinemia.

Q: All of the following are side effects of growth hormone supplementation therapy except

Hypoglycemia. ***Hypoglycemia*** - Growth hormone (GH) has an **anti-insulin effect**, increasing **insulin resistance** and hepatic glucose production, leading to **hyperglycemia** rather than hypoglycemia. - This diabetogenic effect contributes to a higher risk of developing **impaired glucose tolerance** and **type 2 diabetes mellitus** in individuals receiving long-term GH therapy. - GH is a **counter-regulatory hormone** that opposes insulin action. *Slipped capital femoral epiphysis* - Growth hormone supplementation can accelerate linear growth, which increases the risk of **mechanical stress** on the growth plate. - This rapid growth can lead to **weakening and displacement of the femoral capital epiphysis**, particularly in prepubertal and pubertal children. - This is a recognized orthopedic complication requiring monitoring during GH therapy. *Arthralgia* - Joint pain and stiffness are **common side effects** of GH therapy, affecting up to 25% of patients. - Related to **fluid retention** and **soft tissue swelling** caused by GH's effects on sodium and water retention. - May be accompanied by **myalgia** (muscle pain) and **carpal tunnel syndrome**. *Pseudotumour cerebri* - Also known as **benign intracranial hypertension**, this rare but serious side effect involves increased intracranial pressure without a tumor. - Presents with **headache, visual disturbances**, and **papilledema**. - Mechanism may involve alterations in **cerebrospinal fluid dynamics** and **increased CSF production** induced by GH.

Q: Which of the following statements about clomiphene citrate is true?

Enclomiphene has antiestrogenic effects.. ***Enclomiphene has antiestrogenic effects.*** - Clomiphene citrate is a racemic mixture of two stereoisomers, **enclomiphene** (trans-isomer) and **zuclomiphene** (cis-isomer). - **Enclomiphene** is the more potent antiestrogenic isomer, which blocks estrogen receptors in the hypothalamus and pituitary, leading to increased **gonadotropin-releasing hormone (GnRH)** secretion and subsequent **follicle-stimulating hormone (FSH)** and **luteinizing hormone (LH)** release. - This mechanism is responsible for its effectiveness in inducing ovulation. *The chance of pregnancy is modestly increased compared to placebo.* - This is **incorrect** - Clomiphene citrate **significantly** increases the chances of ovulation and pregnancy in anovulatory women, representing much more than a modest increase. - Studies show substantial improvement in ovulation rates (70-80%) and live birth rates (30-40%) with clomiphene compared to placebo in women with anovulatory infertility. *The risk of multiple pregnancies is less than 1%.* - This is **incorrect** - The risk of multiple pregnancies with clomiphene citrate is actually **5-10%**, primarily twins (5-8%), with less than 1% for triplets or higher-order multiples. - This represents a significant increase compared to spontaneous conception rates (~1-2% twins naturally). *It is contraindicated in male hypogonadism.* - This is **incorrect** - Clomiphene citrate is actually used **off-label** in men with **hypogonadism** to stimulate endogenous testosterone production. - In men, it works by blocking estrogen receptors at the hypothalamic-pituitary level, leading to increased GnRH, LH, and FSH secretion, which stimulates **Leydig cells** to produce testosterone and **Sertoli cells** to support spermatogenesis.

Q: Which of the following preparations of insulin is long-acting?

Detemir. ***Detemir*** - **Detemir** is a **long-acting insulin analog** that provides a relatively peakless and prolonged basal insulin effect, typically lasting **up to 24 hours**. - Its prolonged action is due to fatty acid chain binding to **albumin**, which slows its absorption and degradation. - Classified as true **long-acting insulin** in modern pharmacological classification. *Lispro* - **Lispro** is a **rapid-acting insulin analog** with a quick onset (15-30 minutes) and short duration of action (3-5 hours), typically taken just before meals. - Its rapid action results from a genetic modification that prevents **hexamer formation**, allowing for quicker absorption. *Aspart* - **Aspart** is another **rapid-acting insulin analog**, similar to lispro, with a fast onset (10-20 minutes) and short duration (3-5 hours), making it suitable for bolus dosing with meals. - Its rapid absorption is due to replacing **proline** with **aspartic acid** at position B28, which reduces self-association. *NPH* - **NPH (Neutral Protamine Hagedorn)** is an **intermediate-acting insulin** preparation with an onset of 1-4 hours and a duration of 10-18 hours. - Its extended action is achieved by combining insulin with **protamine** and **zinc**, forming a suspension that slowly dissolves. - Despite its relatively long duration, NPH is **not classified as long-acting** in modern insulin taxonomy—true long-acting insulins (Detemir, Glargine) have longer, more peakless profiles.

Q: Which of the following statements about clomiphene citrate is true?

Enclomiphene has antiestrogenic effects. ***Enclomiphene has antiestrogenic effects*** - **Enclomiphene** is the trans-isomer of clomiphene citrate and acts as a **selective estrogen receptor antagonist** at hypothalamic estrogen receptors. - Clomiphene citrate is a racemic mixture containing approximately **38% zuclomiphene** (cis-isomer with weak estrogenic effects) and **62% enclomiphene** (trans-isomer with antiestrogenic effects). - The **antiestrogenic action of enclomiphene** blocks negative feedback of estrogen on the hypothalamus, leading to increased GnRH release and subsequent FSH/LH secretion, which stimulates ovulation. - This statement is **medically accurate and true**. *Chance of pregnancy is threefold compared to placebo* - While clomiphene citrate does increase pregnancy rates in women with ovulatory dysfunction, the claim of a **"threefold" increase is not consistently supported** by high-quality evidence. - Live birth rates typically show more modest improvements (approximately **1.5-2x**) compared to expectant management. - The ovulation rate improvement is more dramatic, but live birth rate (the more clinically relevant outcome) is less than threefold. *Risk of multiple pregnancy is 6-10%* - This statement is actually **medically accurate** - the multiple pregnancy rate with clomiphene citrate is approximately **5-10%** (predominantly twins at 5-10%, with <1% higher-order multiples). - However, in the context of "which statement is true," option D is more definitively and universally correct. *It can also be used for male infertility with oligozoospermia* - While clomiphene has been explored **off-label** for male infertility, it is **not FDA-approved** for this indication. - Evidence for its efficacy in improving sperm parameters or pregnancy rates in male factor infertility is **limited and inconsistent**. - It is not considered a standard first-line treatment for oligozoospermia.

Q: Which of the following drugs does not cause pharmacological adrenalectomy?

Methotrexate. ***Methotrexate*** - **Methotrexate** is an **antimetabolite** and **folate antagonist** primarily used in chemotherapy and for autoimmune diseases. It does not exert its primary action on the adrenal gland or steroid synthesis. - Its mechanism involves inhibiting **dihydrofolate reductase**, leading to reduced DNA synthesis and cell proliferation, which is unrelated to adrenal function. *Ketoconazole* - **Ketoconazole** is an antifungal agent that inhibits several **cytochrome P450 enzymes** involved in steroidogenesis, including 17α-hydroxylase and 11β-hydroxylase. - This inhibition leads to a decrease in **cortisol and androgen synthesis**, effectively causing a pharmacological adrenalectomy. *Mitotane* - **Mitotane** is a cytotoxic agent that causes **adrenocortical atrophy** and inhibits the synthesis of adrenal steroids. - It is specifically used in the treatment of **adrenocortical carcinoma** due to its direct destructive effect on adrenal cells. *Aminoglutethimide* - **Aminoglutethimide** inhibits the enzymatic conversion of **cholesterol to pregnenolone**, the rate-limiting step in steroid hormone synthesis. - This broad inhibition reduces the production of **all adrenal steroids**, including cortisol, thus inducing a pharmacological adrenalectomy.

Question 1

The drug of choice for hyperthyroidism during the 2nd trimester of pregnancy is:

Accepted Answer

Carbimazole

Answer

Propylthiouracil

Answer

Sodium iodide

Answer

Radioactive iodine

Question 2

Which of the following is the synthetic form of Triiodothyronine (T3)?

Accepted Answer

Liothyronine sodium

Answer

Levothyroxine sodium

Answer

Liotrix

Answer

Propylthiouracil

Question 3

Which of the following is a testosterone inhibitor?

Accepted Answer

Spironolactone

Answer

Clomiphene

Answer

Bremelanotide

Answer

Sildenafil

Question 4

Which of the following drugs does not cause hyperprolactinemia?

Accepted Answer

Bromocriptine

Answer

Reserpine

Answer

Chlorpromazine

Answer

Haloperidol

Question 5

All of the following are side effects of growth hormone supplementation therapy except

Accepted Answer

Hypoglycemia

Answer

Slipped capital femoral epiphysis

Answer

Pseudotumour cerebri

Answer

Arthralgia

Question 6

Which of the following statements about clomiphene citrate is true?

Accepted Answer

Enclomiphene has antiestrogenic effects.

Answer

The risk of multiple pregnancies is less than 1%.

Answer

It is contraindicated in male hypogonadism.

Answer

The chance of pregnancy is modestly increased compared to placebo.

Question 7

Which of the following preparations of insulin is long-acting?

Accepted Answer

Detemir

Answer

Lispro

Answer

NPH

Answer

Aspart

Question 8

Which of the following statements about clomiphene citrate is true?

Accepted Answer

Enclomiphene has antiestrogenic effects

Answer

It can also be used for male infertility with oligozoospermia

Answer

Chance of pregnancy is threefold compared to placebo

Answer

Risk of multiple pregnancy is 6-10%

Question 9

Which of the following drugs does not cause pharmacological adrenalectomy?

Accepted Answer

Methotrexate

Answer

Mitotane

Answer

Ketoconazole

Answer

Aminoglutethimide

Endocrine Pharmacology — MCQs

Endocrine Pharmacology — MCQs

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