[The differential diagnosis of constitutional delay of puberty and hypogonadotropic hypogonadism in boys].

Background: The problem of differential diagnosis of constitutional delay of puberty/CDP and hypogonadotropic hypogonadism/HH in boys is discussed, as boys have similar genetic mechanisms and appearance.

Aims: to determine accuracy of the criteria for the differential diagnosis of CDP and HH.

Materials: The study included 56 boys 14.4±0.7 years old with delayed puberty (G1P1-3/testicular volume <3 сm3). We excluded patients with hypergonadotropic hypogonadism, treated with sex steroids or gonadotropins for 12 months, with endocrine/somatic diseases affecting puberty. At the first visit, we evaluated anthropometric data, bone age, testicular volume, hormones and the results of the gonadotropin-releasing hormone test (GnRH) agonist test and the human chorionic gonadotropin test (hCG) test. The HH was defined by a testicular volume <3 сm3 after 2 years follow-up. The patients were divided into two groups: the first group with CDP and testicles ≥3 cm3 (n=50) and the second group with HH and testicles <3 cm3 (n=6).

Results: At the first visit in boys with CDP corrected target height was less (Me SDS –1.8 vs –0,4, р=0.02), bone age was less (Ме SDS –2.5 vs –0.2 р=0.03), testicular volume was more (Ме 1.9 vs 0.5, p=0.0003), hormones were significantly higher, such as LH (Ме 1.1 vs 0.1 mIU/ml, p=0.0002), FSH (Ме 1.9 vs 0.2 IU/l, p=0.00007), inhibin B (Ме 142.3 vs 31.3 pg/ml, p=0.00009), max LH (Ме 18.9 vs 0.6 mIU/ml, p=0.00007), max LH/FSH (Ме 2.3 vs 0.4, p=0.0002) on the GnRH agonist test and Δ testosterone (Ме 14.4 vs 1.1 nmol/l, p=0.0001) on the hCG test than in boys with HH. The LH ≥0.3 mIU/ml had 86% sensitivity, 100% specificity; max LH/FSH ≥1 – 92% sensitivity, 100% specificity; Δ testosterone ≥2.7 nmol/l on the hCG test – 98% sensitivity, 100% specificity for differential diagnosis of CDP and HH in boys. However, max LH ≥3.5 mIU/ml on the GnRH agonist test, FSH ≥0.5 IU/l, inhibin B ≥58 pg/ml had 100% sensitivity and specificity for diagnosis of CDP.

Conclusions: The inhibin B ≥58 pg/ml, LH ≥0.3 mIU/ml, FSH ≥0.5 IU/l or max LH ≥3.5 mIU/ml, max LH/FSH ≥1,0 on the GnRH agonist test, Δ testosterone ≥2.7 nmol/l on the hCG test have an excellent accuracy for the differential diagnosis of CDP and HH in prepubertal boys with delayed puberty.