Question
Which of the following conditions are causes of gonadotropin-releasing hormone (GnRH)-dependent precocious puberty?
1. Constitutional
2. Tubercular encephalitis
3. McCune-Albright syndrome
4. Primary hypothyroidism
| A. |
A. 1, 2, and 3 |
| B. |
1, 2, and 4 |
| C. |
1, 3, and 4 |
| D. |
2, 3, and 4 |
|
Correct Answer » B Explanation |
 |
Clinical Reasoning for the Correct Answer:
– GnRH-dependent (central) precocious puberty: Also called “true” precocious puberty; caused by early activation of the hypothalamic-pituitary-gonadal axis.
– Constitutional: The most common cause; refers to idiopathic or familial (normal variation) early activation of GnRH secretion.
– Tubercular encephalitis: Any lesion or infection affecting the central nervous system (CNS) near the hypothalamus (including tuberculosis, tumors, trauma, or encephalitis) can trigger early GnRH release.
– Primary hypothyroidism: Rarely, severe hypothyroidism (Van Wyk-Grumbach syndrome) can result in gonadotropin-dependent puberty due to increased thyrotropin-releasing hormone (TRH) cross-stimulating gonadotropes.
– Why Option 1 (Constitutional):
– – Idiopathic or familial causes account for most central/GnRH-dependent cases.
– Why Option 2 (Tubercular encephalitis):
– – CNS infections (tubercular or other) can cause premature hypothalamic activation.
– Why Option 3 (McCune-Albright syndrome) is incorrect:
– – McCune-Albright syndrome causes peripheral (GnRH-independent) precocious puberty due to autonomous hormone production from ovarian cysts or adrenal glands.
– – It is a classic cause of GnRH-independent (pseudo-precocious) puberty.
– – Other classic peripheral causes: adrenal tumors, exogenous sex steroids.
– Why Option 4 (Primary hypothyroidism):
– – Severe primary hypothyroidism sometimes paradoxically activates the gonadotropin axis centrally (rare but well-described).
– Why Option A is incorrect:
– – Includes McCune-Albright syndrome, which is a peripheral cause.
– Why Option B is correct:
– – Includes only GnRH-dependent causes (constitutional, CNS disease, severe primary hypothyroidism).
– Why Option C is incorrect:
– – McCune-Albright syndrome included— not a central cause.
– Why Option D is incorrect:
– – Omits constitutional while including McCune-Albright; latter is not central/GnRH-dependent.
