Primary hypothyroidism is characterised by:

DSSSB October 2024

Medical & Surgical Nursing

Easy

Appeared in: DSSSB October 2024

Explanation

In primary hypothyroidism, the defect lies within the thyroid gland itself, causing it to underproduce thyroid hormones (T3 and T4).
The pituitary gland detects the low levels of T3 and T4 in the blood.
Due to the lack of negative feedback from T3/T4, the pituitary gland increases its production of Thyroid-Stimulating Hormone (TSH).
This results in the characteristic laboratory profile of high TSH and low T3/T4 levels.
Among the choices, an increased TSH is the most defining feature presented.

Option B: This option is incorrect because in primary hypothyroidism, T3 and T4 levels are decreased, and metabolism is also decreased, not normal.
Option C: This is incorrect. Metabolism is decreased in hypothyroidism due to the lack of thyroid hormones, which regulate the body's metabolic rate.
Option D: This is incorrect. In primary hypothyroidism, the thyroid gland is failing, leading to decreased production and levels of T3 and T4.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pathophysiology and characteristic laboratory findings of primary hypothyroidism as background academic context rather than a clinical decision trigger.
TSH is the most sensitive marker for diagnosing and managing primary hypothyroidism. Nurses must understand its significance when reviewing lab results and educating patients.
Untreated or poorly managed hypothyroidism can lead to myxedema coma, a life-threatening medical emergency characterized by severe hypothermia, bradycardia, and altered mental status, requiring immediate intervention.
What if? If a patient's lab results showed low TSH and low T3/T4, the nurse should suspect secondary hypothyroidism. This indicates the problem is likely with the pituitary gland, not the thyroid, requiring a different diagnostic and treatment approach.

How to Approach the Question

First, identify the key term in the question: 'Primary hypothyroidism'.
Recall the meaning of 'primary' in endocrine disorders. It signifies that the problem originates in the target gland itself—in this case, the thyroid gland.
Think through the hormonal feedback loop. If the thyroid gland is failing (primary hypothyroidism), it cannot produce enough T3 and T4. This leads to low levels of T3 and T4.
Consider how the pituitary gland responds. It will sense the low T3/T4 and increase the secretion of TSH to try and stimulate the thyroid.
Synthesize the expected lab findings: Low T3/T4 and High TSH.
Evaluate the given options based on this understanding. Option A ('Only increased TSH') is the only choice that correctly identifies a key feature, even if it's not the complete picture. The other options describe hyperthyroidism or are physiologically inconsistent.

Concept Tested & Keywords

Concept Tested: Pathophysiology and characteristic laboratory findings of primary hypothyroidism.
Stem keywords: Primary hypothyroidism, characterised by
Lead-in keywords: characterised by
Negative lead-in flag: false

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E6 Textbook of Biochemistry for medical StudentsDM Vasudevan Part 2 — Subpart B (pp 240-463 of 478) pp. 153-155, 152-154