In a 14-year-old adolescent with delayed puberty and underdeveloped genitalia, which initial diagnostic tests are most appropriate?

In a 14-year-old adolescent with delayed puberty and underdeveloped genitalia, which initial diagnostic tests are most appropriate?

• A. Thyroid function tests, a bone age determination, and a complete blood count
• B. Tests to determine plasma LH and FSH levels and bone age
• C. Radiographic examination of the spine, tests to determine the plasma FSH level, and thyroid function studies
• D. Sedimentation rate, FSH, and bone age

Answer: (B)

When evaluating delayed puberty in a adolescent with underdeveloped genitalia, the key step is to determine whether the delay is due to insufficient central (hypogonadal) drive or a primary gonadal problem. Measuring the pituitary gonadotropins (LH and FSH) and assessing skeletal maturity with bone age directly address that distinction. LH and FSH tell you how the hypothalamic-pituitary-gonadal axis is functioning. If these hormones are low or inappropriately normal for the stage of puberty, it points toward central (hypogonadotropic) hypogonadism. If LH and FSH are elevated despite delayed genital development, it suggests primary gonadal failure, where the gonads aren’t responding to stimulation. Bone age provides context about maturational delay and helps interpret whether the delay aligns with a constitutional delay or a more systemic issue. Other tests like CBC, ESR, or broad thyroid screening aren’t as targeted for this initial differentiation in puberty timing, and imaging of the spine isn’t a first-line requirement for evaluating pubertal onset. Thyroid function can be considered if there are signs pointing to thyroid disease, but the most informative initial tests here are the gonadotropins and bone age. So, the best initial approach is to obtain plasma LH and FSH levels and determine bone age.

When evaluating delayed puberty in a adolescent with underdeveloped genitalia, the key step is to determine whether the delay is due to insufficient central (hypogonadal) drive or a primary gonadal problem. Measuring the pituitary gonadotropins (LH and FSH) and assessing skeletal maturity with bone age directly address that distinction.

LH and FSH tell you how the hypothalamic-pituitary-gonadal axis is functioning. If these hormones are low or inappropriately normal for the stage of puberty, it points toward central (hypogonadotropic) hypogonadism. If LH and FSH are elevated despite delayed genital development, it suggests primary gonadal failure, where the gonads aren’t responding to stimulation. Bone age provides context about maturational delay and helps interpret whether the delay aligns with a constitutional delay or a more systemic issue.

Other tests like CBC, ESR, or broad thyroid screening aren’t as targeted for this initial differentiation in puberty timing, and imaging of the spine isn’t a first-line requirement for evaluating pubertal onset. Thyroid function can be considered if there are signs pointing to thyroid disease, but the most informative initial tests here are the gonadotropins and bone age.

So, the best initial approach is to obtain plasma LH and FSH levels and determine bone age.