Body Composition in Infants With Klinefelter Syndrome and Effects of Testosterone Treatment

Serum Luteinizing Hormone (LH)

Serum will be collected at the first study visit prior to randomization. Ultrasensitive LH will be measured.

Time frame: baseline only

Serum Follicle Stimulating Hormone (FSH)

Serum will be collected at the first study visit prior to randomization. Ultrasensitive FSH will be measured.

Time frame: baseline only

Serum Total Testosterone

Serum will be collected at the first study visit prior to randomization. Total testosterone by mass spectroscopy will be measured.

Time frame: baseline only

Serum Inhibin B (INHB)

Serum will be collected at the first study visit prior to randomization. Inhibin B levels will be measured.

Time frame: baseline only

Serum Anti-Mullerian Hormone (AMH)

Serum will be collected at the first study visit prior to randomization. AMH levels will be measured.

Time frame: baseline only

Leptin

Serum will be collected at the first study visit prior to randomization. Leptin levels will be measured.

Time frame: baseline only

Change in Raw Score on the Alberta Infant Motor Scale

Muscle tone and motor development will be assessed by an occupational therapist using the standardized Alberta Infant Motor Scale (AIMS). The AIMS scale measures infant motor maturation from birth until the age of independent walking. An occupational therapists assesses 58 motor behavior items in 4 position categories: prone (21 items), supine (9 items), sitting (12 items) \& standing(16 standing). Each item receives one point (range of raw scores 0-58), with higher scores indicating more skills acquired. For change in scores, the raw score at 3 months was subtracted from the baseline raw score.

Time frame: 3 months

Change in Score on the Movement Assessment of Infants (MAI)

Muscle tone and motor development will be assessed by an occupational therapist using the standardized Movement Assessment of Infants (MAI). The MAI evaluates four domains: muscle tone, primitive reflex, automatic reactions and volitional movement. All items are scored 1-5 and summed to generate a "Total Risk Score". Lower scores indicate better function, and Total Risk Scores of 8 or more indicate high risk.

Time frame: 3 months

Change in Total Motor Standard Score on the Peabody Developmental Motor Scales 2

Motor development will be assessed by an occupational therapist using the standardized Peabody Developmental Motor Scales 2. Standard scores are normalized to age with a mean of 100 and standard deviation of 15. Change in standard score was calculated as the differences between the subject's standard score at 3 months minus the standard score at baseline. A positive change in standard scores would indicate greater growth on the measure relative to peers, while a negative number would indicate slower growth on the measure relative to peers.

Time frame: 3 months

Change in Penile Length

Stretched penile length will be measured by a physician before randomization and at the end of the study period.

Time frame: Baseline and 3 months

Change in Fat Free Mass

Fat free mass (lean mass) will be measured using air displacement plethysmography (PEA POD) at the beginning and end of the study period.

Time frame: Baseline and 3 months