Q4
4 marksSection A

Question numbers 4(a) - 4(d) are based on the table and related information in the passage given below.

Thyroid Stimulating Hormone (TSH) stimulates thyroid gland to produce thyroxine. Study the table given below.


Table: TSH levels during pregnancy

Stage of pregnancy | Normal (mU/L) | Low (mU/L) | High (mU/L)

First trimester | 0.2 – 2.5 | < 0.2 | 2.5 – 10

Second trimester | 0.3 – 3.0 | < 0.3 | 3.01 – 4.5

Third trimester | 0.8 – 5.2 | < 0.8 | > 5.3


It is important to monitor TSH levels during pregnancy. High TSH levels and hypothyroidism can especially affect chances of miscarriage. Therefore, proper medication in consultation with a doctor is required to regulate/control the proper functioning of the thyroid gland.


4(a) Give the full form of TSH.

4(b) State the main function of TSH.

4(c) Why do TSH levels in pregnant women need to be monitored?

4(d) A pregnant woman has TSH level of 8.95 mU/L8.95 \text{ mU/L}. What care is needed for her?

Control and Coordination
Hormones in Animals
Official Answer

4(a) The full form of TSH is Thyroid Stimulating Hormone.


4(b) The main function of TSH is to stimulate the thyroid gland to produce and secrete the hormone thyroxine.


4(c) TSH levels in pregnant women need to be monitored because abnormal levels—especially high TSH levels indicating hypothyroidism—can significantly increase the risk of miscarriage and adversely affect the neurological development of the fetus.


4(d) A TSH level of 8.95 mU/L8.95 \text{ mU/L} is abnormally high compared to the normal reference ranges across all trimesters (normal ranges: 0.2−2.5 mU/L0.2 - 2.5 \text{ mU/L} in the first trimester, 0.3−3.0 mU/L0.3 - 3.0 \text{ mU/L} in the second, and 0.8−5.2 mU/L0.8 - 5.2 \text{ mU/L} in the third). This indicates hypothyroidism. The patient requires immediate consultation with an endocrinologist/doctor to start appropriate hormone replacement therapy (such as synthetic thyroxine) to normalize her TSH levels and safeguard the pregnancy.

Thyroid Stimulating Hormonethyroxinemiscarriagehypothyroidismmedicationdoctor consultation

Marking Scheme

  • 14(a): 1 Mark for correctly writing 'Thyroid Stimulating Hormone'.
  • 24(b): 1 Mark for stating that TSH stimulates the thyroid gland to produce thyroxine.
  • 34(c): 1 Mark for explaining that monitoring is essential to prevent miscarriage and support proper fetal development.
  • 44(d): 1 Mark for identifying the level as high/hypothyroidism and recommending immediate medical consultation/medication.

Hint

Compare the given TSH value of 8.95 mU/L8.95 \text{ mU/L} with the normal ranges provided in the table for each trimester to identify if it is normal, low, or high, and recall the consequences of high TSH mentioned in the passage.

Quick Oral Answer

Q: Which gland secretes Thyroid Stimulating Hormone (TSH)? A: TSH is secreted by the pituitary gland, which is located at the base of the brain. Q: What is the main symptom of iodine deficiency in adults? A: Iodine deficiency leads to goitre, which is characterized by an enlargement of the thyroid gland, causing a visible swelling in the neck.

Analysis & Explanation

The endocrine system plays a vital role in maintaining homeostasis and coordinating physiological processes, especially during critical periods like pregnancy.


  1. TSH Regulation: Thyroid Stimulating Hormone (TSH) is secreted by the anterior pituitary gland. It acts on the thyroid gland to regulate the synthesis and release of thyroid hormones, primarily thyroxine (T4T_4).
  2. Role of Thyroxine: Thyroxine regulates carbohydrate, protein, and fat metabolism in the body to provide the optimal balance for growth and development. During early pregnancy, the fetus relies entirely on maternal thyroxine for brain development before its own thyroid gland becomes functional.
  3. Feedback Mechanism: When thyroxine levels in the blood are low, the pituitary gland secretes more TSH to stimulate the thyroid gland. Therefore, a high TSH level (8.95 mU/L8.95 \text{ mU/L}) is a clinical indicator of hypothyroidism (underactive thyroid).
  4. Clinical Action: To prevent complications like miscarriage or developmental delays in the fetus, external administration of thyroid hormone (levothyroxine) is prescribed to bring TSH back to the normal trimester-specific range.

Common Mistakes

  1. 1Confusing high TSH with hyperthyroidism: Students often mistakenly assume high TSH means an overactive thyroid. In reality, high TSH indicates hypothyroidism because the pituitary is working harder to stimulate a sluggish thyroid gland.
  2. 2Failing to refer to the table: Not comparing the value of 8.95 mU/L8.95 \text{ mU/L} with the trimester-specific normal ranges to conclude that it is abnormally high.
  3. 3Spelling errors in hormone names: Writing 'thyroxin' or 'thyroid' incorrectly.

Interesting Facts

Iodine is an essential element required by the thyroid gland to synthesize thyroxine. This is why dietary salt is iodized to prevent thyroid disorders like goitre.

During the first trimester of pregnancy, the fetus is completely dependent on maternal thyroid hormones because the fetal thyroid gland does not begin functioning until about the 12th week of gestation.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2020?

This question carries 4 marks in the CBSE Class 10 Science 2020 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Control and Coordination" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Hormones in Animals" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2020 paper?

This question appears in Section A in the CBSE Class 10 Science 2020 paper.