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Objectives: Children with Prader-Willi Syndrome (PWS) may develop premature pubarche (PP). We studied the incidence of PP and potential precursors and consequences.

Methods: A chart review of children with PWS treated at Children’s Mercy Hospital between 1990 – 2021 was performed. Patients not seen in endocrine clinic or without documentation of pubarche were excluded. PP was defined as Tanner stage 2 (TS2) pubic hair in girls < 8 and boys < 9 years old. Gonadarche was defined as having TS2 breast development or testicular volume ≥4 mL. Bone age (BA) divided by chronological age (CA) was used as an index for BA advancement. Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) was calculated as (Fasting insulin, uIU/mL)*(Fasting glucose, mg/dL)/405. Small for gestational age (SGA) was defined as birth weight less than the 10% for age. T2D was defined as having a HbA1c ≥6.5%. Wilcoxon rank-sum, Fisher’s exact, and Kendall rank correlation coefficient (CC) were used.

Results: Analysis included 43 children with PWS, 23 (53.4%) with PP and 20 (46.5%) with normal pubarche (NP). Average age of pubarche was 6.48 ± 0.92 years in PP group and 9.9 ± 1.59 years in NP group. Three patients in PP group and one patient in NP group were treated for central precocious puberty with gonadotropin releasing hormone agonist therapy, but median age at gonadarche did not differ between the groups. No significant differences in sex, race, mutation type, or SGA status existed between groups. Age at pubarche was not correlated with age of rhGH initiation, BMI z-score, or HOMA-IR at pubarche. BMI z-score at pubarche was modestly correlated with degree of pubarchal BA advancement (CC=0.311, p=0.033), but the correlation with difference between final and target height was non-significant (CC=-0.081, p=0.68). Highest HbA1c after pubarche was in the pre-diabetes range at 5.8% [IQR 5.6, 6.1] in PP group and 5.6% [IQR 5.4, 6.0] in NP group (p=0.356), though frequency of T2D after pubarche did not differ between groups. Those with PP were more likely to have a lower HDL (p=0.041). The difference between target and final height did not differ between groups (p=0.507).

Conclusion: Premature pubarche is common in PWS but does not impact discrepancy from final height, though obesity at pubarche results in advanced bone age. Obesity and insulin resistance may not be the cause of premature pubarche in children with PWS, contrary to what has been seen in obese children without PWS.

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Premature Pubarche in Prader-Willi Syndrome: Potential Predictors and Consequences