Answer: Early Development of Secondary Sexual Characteristics
The exception is option 3 - both true precocious puberty and pseudo precocious puberty present with early development of secondary sexual characteristics, making this the feature that does NOT differentiate between them.
Key Distinguishing Features
What Both Types Share (The Exception)
- Early development of secondary sexual characteristics occurs in BOTH true and pseudo precocious puberty 1, 2, 3
- Both conditions manifest with phenotypically appropriate sexual maturation before age 8 in girls and age 9 in boys 2, 4
- Breast development (thelarche) in girls appears early in both types 5, 6
What Actually Differentiates Them
Presence of Gametogenesis:
- True precocious puberty (central/gonadotropin-dependent) involves complete activation of the hypothalamic-pituitary-gonadal axis with gametogenesis present 1, 2
- Pseudo precocious puberty (peripheral/gonadotropin-independent) produces sex steroids WITHOUT gametogenesis, as gonadotropins remain suppressed 7
Gonadotropin Secretion Pattern:
- Critical error in the question: Gonadotropins are secreted from the anterior pituitary, NOT posterior pituitary 8
- True precocious puberty shows elevated basal and GnRH-stimulated LH/FSH levels indicating hypothalamic-pituitary axis activation 1, 2
- Pseudo precocious puberty demonstrates prepubertal or suppressed gonadotropin levels despite pubertal sex steroid concentrations 7
- The hypothalamus controls gonadotropin release through GnRH secretion 8
Gender Predominance:
- True precocious puberty is significantly more common in females, with girls having higher risk of central nervous system abnormalities when presenting before age 6 5
- The female predominance is well-established for central/true precocious puberty 5, 2
Clinical Pitfall
The question contains an anatomical error stating "posterior pituitary" when gonadotropins (LH and FSH) are secreted from the anterior pituitary under hypothalamic control 8. This is a fundamental endocrine principle that should not be confused.