Introduction: Diethylstilbestrol (DES) is a synthetic nonsteroidal estrogen historically prescribed during pregnancy and used as a growth promoter, now recognized as a potent endocrine disruptor. For B. Pharm students, mastering DES pharmacology includes its chemical class (stilbene derivative), estrogen receptor agonism, pharmacokinetics, hepatic metabolism, teratogenic and carcinogenic risks, and regulatory history (FDA ban in 1971). Prenatal DES exposure causes reproductive tract malformations, vaginal adenosis and clear cell adenocarcinoma in daughters, plus fertility issues in exposed offspring. Understanding mechanisms such as estrogen-receptor mediated proliferation and epigenetic alterations is essential for clinical counseling, toxicology and pharmacovigilance. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is diethylstilbestrol (DES)?
- Synthetic nonsteroidal estrogen
- Natural steroidal estrogen
- Selective estrogen receptor modulator
- Pure anti-estrogen
Correct Answer: Synthetic nonsteroidal estrogen
Q2. What was a primary historical clinical use of DES?
- Treatment of acne
- Prevention of miscarriage and threatened abortion during pregnancy
- First-line therapy for prostate cancer
- Topical therapy for dermatitis
Correct Answer: Prevention of miscarriage and threatened abortion during pregnancy
Q3. Why was DES withdrawn from recommended use in pregnant women?
- Caused acute liver failure in mothers
- Linked to clear cell adenocarcinoma and reproductive tract abnormalities in exposed offspring
- Proved ineffective for all indications
- Was replaced by cheaper steroid hormones
Correct Answer: Linked to clear cell adenocarcinoma and reproductive tract abnormalities in exposed offspring
Q4. DES exerts its primary pharmacologic effects by binding to which target?
- Estrogen receptors (ERα and ERβ)
- Androgen receptors
- Progesterone receptors
- Glucocorticoid receptors
Correct Answer: Estrogen receptors (ERα and ERβ)
Q5. Chemically, DES belongs to which class?
- Stilbene derivative
- Steroid nucleus compound
- Peptide hormone
- Thyroid analogue
Correct Answer: Stilbene derivative
Q6. Which malignancy is classically associated with in utero DES exposure in female offspring?
- Clear cell adenocarcinoma of the vagina and cervix
- Ovarian germ cell tumor
- Endometrial stromal sarcoma
- Squamous cell carcinoma of the vulva
Correct Answer: Clear cell adenocarcinoma of the vagina and cervix
Q7. Maternal exposure to DES is associated with increased risk of which condition in the mother?
- Breast cancer
- Pancreatic cancer
- Multiple sclerosis
- Chronic myelogenous leukemia
Correct Answer: Breast cancer
Q8. Common reproductive abnormality reported in males exposed to DES in utero is:
- Epididymal cysts and structural abnormalities of the testes
- Prostate cancer in adolescence
- Persistent Müllerian duct syndrome
- Complete androgen insensitivity
Correct Answer: Epididymal cysts and structural abnormalities of the testes
Q9. Major pathways for DES metabolism include:
- Hepatic hydroxylation and conjugation (phase I and II reactions)
- Renal excretion unchanged only
- Metabolism exclusively by gut flora
- Rapid cleavage to peptides
Correct Answer: Hepatic hydroxylation and conjugation (phase I and II reactions)
Q10. DES can be best described pharmacodynamically as:
- A potent full agonist at estrogen receptors
- An irreversible estrogen receptor antagonist
- An aromatase inhibitor
- A selective progesterone receptor modulator
Correct Answer: A potent full agonist at estrogen receptors
Q11. Mechanisms implicated in DES-induced carcinogenesis include:
- Estrogen receptor–mediated proliferation and epigenetic modifications
- Direct alkylation of DNA bases only
- Inhibition of DNA repair enzymes exclusively
- Generation of prions
Correct Answer: Estrogen receptor–mediated proliferation and epigenetic modifications
Q12. Recommended screening for women with in utero DES exposure generally includes:
- Regular gynecologic exam with cervical cytology and colposcopy if abnormal
- Annual whole-body CT scans
- Routine liver biopsy every five years
- No special screening beyond general population guidelines
Correct Answer: Regular gynecologic exam with cervical cytology and colposcopy if abnormal
Q13. DES was also used historically in agriculture for:
- Growth promotion in livestock
- Herbicide for crops
- Antibiotic feed additive
- Insect repellent
Correct Answer: Growth promotion in livestock
Q14. DES is classified toxicologically as which of the following?
- Teratogen and endocrine disruptor
- Non-toxic food additive
- Essential nutrient
- Topical antiseptic
Correct Answer: Teratogen and endocrine disruptor
Q15. The critical period for many DES-induced reproductive tract malformations is:
- First and early second trimester (organogenesis of the reproductive tract)
- Third trimester only
- Preconception exposure of the father only
- Postnatal exposure during adolescence
Correct Answer: First and early second trimester (organogenesis of the reproductive tract)
Q16. The peak age range for DES-associated clear cell adenocarcinoma onset in exposed daughters is typically:
- Young adulthood (approximately 15–30 years)
- Childhood (0–5 years)
- Late elderly (>75 years)
- Middle childhood (6–12 years)
Correct Answer: Young adulthood (approximately 15–30 years)
Q17. Vaginal adenosis seen in DES-exposed females is characterized by:
- Presence of columnar epithelium within the vaginal mucosa
- Keratinized squamous overgrowth only
- Complete absence of vagina
- Excessive keratin deposition in the cervix
Correct Answer: Presence of columnar epithelium within the vaginal mucosa
Q18. Definitive diagnosis of DES-related neoplasia requires:
- Biopsy and histopathological examination
- Serum DES concentration decades after exposure
- Urine culture
- Routine chest X-ray
Correct Answer: Biopsy and histopathological examination
Q19. Long-term reproductive consequences in DES-exposed offspring commonly include:
- Reduced fertility and increased pregnancy complications
- Complete immunity to estrogenic effects
- Enhanced muscle growth and strength
- Permanent hyperthyroidism
Correct Answer: Reduced fertility and increased pregnancy complications
Q20. In what year did the FDA formally advise against use of DES in pregnancy?
- 1971
- 1960
- 1985
- 1950
Correct Answer: 1971
Q21. The structural motif central to DES is best described as:
- Two phenyl rings joined by an ethene (stilbene) bridge
- Steroid four-ring fused structure
- Linear peptide chain
- Benzodiazepine core
Correct Answer: Two phenyl rings joined by an ethene (stilbene) bridge
Q22. Which obstetric complication is more frequent among DES-exposed daughters?
- Ectopic pregnancy and preterm delivery
- Gestational diabetes exclusively
- Decreased incidence of cesarean section
- Complete absence of labor pain
Correct Answer: Ectopic pregnancy and preterm delivery
Q23. Apart from genomic nuclear ER effects, DES may also produce cellular effects through:
- Non-genomic membrane-associated estrogen receptor signaling
- Direct blocking of insulin receptors
- Activation of prokaryotic ribosomes
- Calcium chelation in plasma only
Correct Answer: Non-genomic membrane-associated estrogen receptor signaling
Q24. Which of the following statements about diagnostic testing for historical DES exposure is true?
- No reliable biochemical test exists decades later; diagnosis is mainly by exposure history and clinical findings
- DES can be easily detected in hair 50 years after exposure
- Standard pregnancy tests detect prior DES exposure
- Complete blood count is diagnostic for DES exposure
Correct Answer: No reliable biochemical test exists decades later; diagnosis is mainly by exposure history and clinical findings
Q25. Epigenetic changes associated with DES exposure may include:
- Altered DNA methylation and histone modification patterns
- Permanent insertion of viral DNA into the genome
- Simple nucleotide deletions only
- Exclusive mitochondrial DNA replication errors
Correct Answer: Altered DNA methylation and histone modification patterns
Q26. The biologically active stereoisomer of DES predominantly used historically is the:
- Trans isomer of diethylstilbestrol
- Cis isomer only
- Racemic steroid mixture
- D-enantiomer peptide form
Correct Answer: Trans isomer of diethylstilbestrol
Q27. Counseling point for a woman known to be a DES daughter includes:
- Informing her about specialized gynecologic surveillance and to report abnormal bleeding
- Recommending avoidance of all vaccinations
- Advising against any future pregnancies under all circumstances
- Saying there are no potential long-term reproductive implications
Correct Answer: Informing her about specialized gynecologic surveillance and to report abnormal bleeding
Q28. One pharmacokinetic reason DES had prolonged oral estrogenic action is that it:
- Is relatively resistant to rapid metabolic inactivation by the liver
- Is rapidly degraded in the stomach to inactive peptides
- Is excreted unchanged within minutes
- Is sequestered in bone permanently
Correct Answer: Is relatively resistant to rapid metabolic inactivation by the liver
Q29. Current scientific use of DES includes:
- Research tool to study estrogen signaling, endocrine disruption and epigenetic effects
- Routine prescription as a contraceptive
- First-line chemotherapy for breast cancer
- Dietary supplement for athletes
Correct Answer: Research tool to study estrogen signaling, endocrine disruption and epigenetic effects
Q30. Which statement best describes regulatory status of DES today?
- Use in pregnancy and as a livestock growth promoter is banned in many countries due to safety concerns
- It is approved as a first-line treatment for menopausal symptoms worldwide
- It is freely available over-the-counter as an herbal extract
- It is required in infant formula for bone growth
Correct Answer: Use in pregnancy and as a livestock growth promoter is banned in many countries due to safety concerns
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
Mail- Sachin@pharmacyfreak.com