Figure 5.

Insulin concentration EC₅₀ for half maximal suppression of R_aFFA. Data represent the EC₅₀ R_aFFA. Each gray-filled symbol represents datum from a lactating or formula-feeding woman who underwent the two-step hyperinsulinemic-euglycemic clamp at low and medium insulin levels (10 and 20 mU/m²/min, respectively). Only 16 of the 18 subjects are reported in the main analysis because 2 subjects did not reach 50% suppression of R_aFFA with the medium-dose infusion. To increase the sample size and to determine whether the choice of clamp protocol insulin levels influenced the calculated EC₅₀ R_aFFA, an additional group of lactating and formula-feeding women (black-filled symbols) underwent an insulin infusion at 10 and 40 mU/m²/min insulin. Only 7 of the 10 subjects are reported from this additional group because 2 did not receive isotopes and 1 did not reach 50% suppression of R_aFFA with the high-dose infusion. The box and whiskers graph represent minimum, maximum, median, and 25th and 75th percentiles. Lastly, the horizontal dotted line represents data from a published study (29) in nonpregnant, nonlactating women for comparison. In that study, the EC₅₀ was calculated from a two-step clamp using insulin infusions of 0.25 and 2.5 mU/kg FFM/min (equivalent to 6 and 60 mU/m²/min when put in the units used in present study).