Endocrine Abstracts (2011) 26 OC2.6

The spectrum and causes of gonadal dysfunction in adolescents and adults with Prader--Willi syndrome (PWS)

Talia Eldar-Geva1,2, Harry J Hirsch1, Fortu Benarroch2 & Varda Gross-Tsur1,2

1Shaare-Zedek Medical Center, Jerusalem, Israel; 2The Hebrew University, Jerusalem, Israel.

Introduction: Hypogonadism is a cardinal feature of PWS and was generally attributed to hypothalamic dysfunction. Recently, however, primary gonadal defects were also documented. We characterized the spectrum and causes of hypogonadism in PWS adolescents and adults.

Methods: We measured reproductive hormonal profiles of 19 males (m) and 16 females (f) ages 15 to 32 years with genetically confirmed PWS. Puberty was assessed by Tanner staging; blood was sampled for gonadotropins, sex-steroids and the gonadal-specific peptides, inhibin B (INB) and anti-Mullerian hormone (AMH).

Results: We found four distinct hormonal profiles based on INB and FSH levels: Group A (m:f; 8:1): hypergonadotrophic (primary gonadal) hypogonadism with elevated FSH levels (>15 IU/l) and undetectable inhibin B. Group B (m:f; 4:4): hypogonadotrophic hypogonadism with FSH<0.5 IU/l and inhibin B<7 pg/ml. Group C (m:f; 3:5): partial gonadal and hypothalamic function with inhibin B>20 pg/ml and FSH 2–10 IU/l. Group D (m:f; 4:6): mild hypothalamic and severe gonadal dysfunction (FSH 0.5–10 IU/l and INB<20 pg/ml). There were significantly more males in Group A versus C or D (P<0.05). Mean breast Tanner stage and testosterone levels were highest in Group C (P<0.03), mean LH was highest in Group A (P<0.001), and mean AMH was highest in Group B (P<0.005). No differences were found in genetic subtype, age and BMI among the four groups.

Conclusion: We characterized four distinct phenotypes of hypogonadism in PWS ranging from primary gonadal to hypothalamic hypogonadism; the minority had gonadotropin deficiency. Determining individual reproductive hormone patterns, including inhibin B, may be important for assessing the possibility of fertility in women and for recommending the need for contraception or hormonal replacement therapy.

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