Neonatal sex-steroid hormones and timidity in 6-18-month-old boys and girls.

Five sex-steroid hormones (testosterone, androstenedione, estradiol, estrone, and progesterone) are assayed in umbilical cord blood. Timidity is assessed in home and laboratory observations by reactions to a range of novel toys in children from 6 to 18 months of age. Significant short- (1 week) and long- (several months) term stability in timidity is demonstrated. Girls have higher mean scores on observed timidity than do boys in 2 of the 3 samples tested. An across-age timidity score is computed which shows significant correlations with neonatal progesterone, testosterone, and estradiol for boys, but is not significantly predicted by hormone concentrations in girls.