Q.166 Zoology ⭐ 360° Option Elimination Active

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NEET 2026 Zoology Question 166 Solution

Topic: Human Reproduction · Official NTA Booklet Code 50

Question

Which of the following hormone is not secreted by human placenta?

(1)hCG
(2)Estrogen
(3)Progesterone
(4)LH

✓

Verified Against NTA Final Answer Key

Option (4) : LH (Luteinizing hormone)

📚 Human Reproduction Easy

📋 Given Parameters & Problem Setup

Endocrine Structure Human Placenta

Criterion Hormone NOT secreted by human placenta

Given Options hCG, hPL, Estrogen, LH

⚡

The 30-Second Exam Hall Shortcut: ⚡ Placental vs. Pituitary Hormone Sieve

⏱️ Save ~35 seconds

Placenta secretes hCG, hPL, Estrogen, Progesterone, Relaxin. LH comes from ANTERIOR PITUITARY!

1 Recall placental endocrine products: hCG (human chorionic gonadotropin), hPL (human placental lactogen), estrogens, and progestogens.

2 LH (Luteinizing Hormone) is a gonadotropin synthesized and secreted exclusively by the anterior pituitary gland (adenohypophysis).

3 hCG mimics LH action on the corpus luteum, but placenta does NOT secrete LH itself.

4 Identify LH as Option (4).

5 Pick Option (4) in under 10 seconds!

🛡️

Why You Can 100% Trust This Shortcut: NCERT Biology · Human Reproduction (Fertilization & Blastocyst Implantation: Trophoblast attaches to endometrium).

📐

Step-by-Step Rigorous Workflow & Mathematical Proof

Step 1

Endocrine Role of the Human Placenta

Placenta acts as an endocrine tissue and produces several hormones like human chorionic gonadotropin (hCG), human placental lactogen (hPL), estrogens, progestogens, and in the later phase of pregnancy, a hormone called relaxin is also secreted by the ovary/placenta.

\text{Placenta} \rightarrow \text{hCG, hPL, Estrogens, Progestogens, Relaxin}

• Hormones like hCG, hPL and relaxin are produced in women only during pregnancy.

Step 2

Origin of Luteinizing Hormone (LH)

Luteinizing hormone (LH) is a pituitary gonadotropin secreted by gonadotroph cells of the anterior pituitary gland under the stimulation of hypothalamic GnRH. It is never synthesized or secreted by placental trophoblasts.

\text{Hypothalamus (GnRH)} \rightarrow \text{Anterior Pituitary} \xrightarrow{\text{Secretes}} \mathbf{LH} \neq \text{Placenta}

• hCG shares structural homology with LH and binds LH receptors to maintain the corpus luteum, but LH itself is strictly of pituitary origin.

⭐

360° Option Elimination Engine Key Feature

Diagnose every choice: Know exactly why the right option works and why distractors fail.

4-Option Deep Scan

1 A

✗ Incorrect

Verdict & Scientific Reason:

Incorrect choice because hCG IS secreted by the syncytiotrophoblast of the human placenta (basis of pregnancy urine test).

⚠️

Student Fallacy (Why candidates pick this trap): Missing the "NOT" in the question stem.

2 B

✗ Incorrect

Verdict & Scientific Reason:

Incorrect choice because hPL IS secreted by the human placenta to stimulate mammary development and regulate fetal glucose metabolism.

⚠️

Student Fallacy (Why candidates pick this trap): Overlooking that "placental" is literally in the name of hPL.

3 C

✗ Incorrect

Verdict & Scientific Reason:

Incorrect choice because estrogens ARE abundantly produced by the feto-placental unit during gestation.

⚠️

Student Fallacy (Why candidates pick this trap): Thinking estrogens are solely produced by ovarian follicles.

4 D

✓ 100% Correct

Verdict & Scientific Reason:

100% correct. LH is secreted by the anterior pituitary, NOT by the human placenta.

💡

Why this is airtight: None; clear endocrine localization.

⚠️

NTA Trap Alert: hCG vs. LH Confusion

Because hCG mimics the luteotropic action of LH to keep the corpus luteum alive, students sometimes confuse the two and think LH is produced by the placenta. Placenta produces hCG, NOT LH.

🛡️ How to avoid the -1 mark: Remember: "P" in hPL = Placenta; "C" in hCG = Chorion/Placenta; "LH" = Anterior Pituitary.

📖

Core NEET Syllabus Standard

NEET Biology Core Syllabus · Human Reproduction Standard Benchmark

Core Scientific Principle Tested:

"Placenta produces hCG, hPL, estrogens, and progestogens; LH is produced by the anterior pituitary."

Syllabus Focus: Pregnancy and Embryonic Development

✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗

Placenta makes hCG & hPL; Pituitary alone produces LH!

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NEET 2026 Zoology Question 166 Solution

Question

The 30-Second Exam Hall Shortcut: ⚡ Placental vs. Pituitary Hormone Sieve

Step-by-Step Rigorous Workflow & Mathematical Proof

Endocrine Role of the Human Placenta

Origin of Luteinizing Hormone (LH)

360° Option Elimination Engine Key Feature

NTA Trap Alert: hCG vs. LH Confusion

Core NEET Syllabus Standard

Ready to attempt under real exam pressure?

🔗 Related Questions — Human Reproduction

Structure and Function of Human Spermatozoon

Chronology of Human Gestational Milestones

Comparison of Spermatogenesis vs Oogenesis and Hormonal Control

Terminology of Menstrual Milestones (Menarche vs Menopause)

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