The present invention provides standard deviation score (SDS) calculators, which SDS calculators are useful for transforming insulin-like growth factor-1 (IGF-1) concentrations to IGF-1 standard deviation scores. In one embodiment, IGF-1 blood levels are calculated so as to take into account IGFBP-3 blood levels (and, optionally, IGF-2 blood levels) to provide an IGF-1 production rate, which can be used to calculate an IGF-1 production rate SDS. The IGF-1 SDS and IGF-1 production rate SDS are particularly useful in assessing the stimulated rate of IGF-1 production in response to, for example, growth hormone therapy.