Sex hormone levels

The panel

Sex hormone testing (testosterone, oestradiol, LH, FSH, SHBG) is used to investigate suspected hypogonadism, menstrual irregularity, and pubertal disorders - interpretation always requires pairing the peripheral hormone level with the pituitary gonadotrophin level to localise the disturbance to central (hypothalamic-pituitary) or peripheral (gonadal) origin
A frequently ordered panel across reproductive endocrinology, from male hypogonadism and female menstrual disorder work-up to delayed/precocious puberty assessment

Low sex hormone with low/inappropriately normal gonadotrophins indicates central (hypothalamic-pituitary) hypogonadism - the gonad itself is intrinsically normal but under-stimulated; low sex hormone with elevated gonadotrophins indicates primary gonadal failure, with the pituitary appropriately attempting to compensate via increased stimulation - this paired interpretation is essential to correctly localise the underlying problem

Timing matters for some tests (e.g. testosterone should ideally be measured in the morning given diurnal variation, with peak levels earlier in the day); SHBG measurement helps interpret total testosterone in states where SHBG itself is altered (e.g. obesity lowers SHBG, potentially causing a falsely low total testosterone despite normal free/bioavailable testosterone)
Repeat confirmation of an abnormal result on a separate occasion is generally recommended before committing to a diagnosis, given biological variability

Central hypogonadism -> further pituitary/hypothalamic work-up (imaging, other pituitary axis testing) given the possibility of a structural or functional cause requiring specific management
Primary gonadal failure -> hormone replacement is generally appropriate without extensive further localisation, since the gonad itself is the identified site of failure

Central vs primary hypogonadism gonadotrophin pattern (the key interpretive principle), obesity-related SHBG reduction and total testosterone interpretation, diurnal testosterone variation and morning sampling, delayed/precocious puberty gonadotrophin pattern interpretation
Sex hormone results should never be interpreted without their paired gonadotrophin level - the same low testosterone or oestradiol value has a completely different diagnostic meaning (and different further work-up) depending on whether LH/FSH is elevated (primary gonadal failure) or low/inappropriately normal (central hypothalamic-pituitary cause)

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