Kisspeptin in the Evaluation of Delayed Puberty

Inclusion Criteria: Adolescent Boys * ages 13.5-17 years * testicular volume \<4 mL OR 4-8 ml with no change in the past 6 months by Prader orchidometer * first morning (before 9AM) LH \<2 mIU/mL and testosterone \<50 ng/dL Adolescent Girls * ages 12-17 years * Tanner stage I OR II breast development with no change in the past 6 months * first morning (before 9AM) LH \<2 mIU/mL and estradiol \<20 pg/ml All Subjects: * bone age less than chronological age * weight ≥ 28 kg * body mass index \>10th percentile and \<+3 SDS for bone age * blood pressure \>5th percentile and \<95th percentile for bone age and height * white blood cell counts, platelet counts, electrolytes, thyroid stimulating hormone (TSH), free thyroxine (T4) within reference range for age * erythrocyte sedimentation rate \<2X the upper limit of the reference range for age * hemoglobin within reference range for girls of the same chronological age * blood urea nitrogen (BUN), creatinine, prolactin not elevated * aspartate aminotransferase (AST) and alanine aminotransferase (ALT) no more than 2X the upper limit of the reference range * Insulin-like growth factor 1 (IGF-1) within reference range for bone age Exclusion Criteria: All Subjects: * history or presence of underlying condition that could cause delayed puberty (chronic illness, weight loss, abnormal cranial magnetic resonance imaging (MRI)) * history of an allergic drug reaction