Table 3

Adjusted^a means of serum IGF-I, IGFBP-3, and molar ratio (IGF-I:IGFBP-3), by reproductive history^b and hormonal variables, Singapore Chinese Health Study

Predictor	Number of subjects	IGF-I (ng/ml)	IGFBP-3 (ng/ml)	Molar ratio (IGF-I:IGFBP-3)*1000
Age at menarche
<17 years	274	128	4233	107
≥17 years	52	112	3956	100
P		0.06	0.04	0.21
Age when periods became regular
<17 years	256	128	4254	106
≥17 years	60	113	3912	103
Never became regular	10	116	3831	102
P for <17 yrs vs. ≥17 yrs		0.06	0.003	0.47
Age at first birth
Nulliparous	20	125	4174	107
≤30 yrs	276	124	4189	104
>30 yrs	30	138	4240	116
P for (nullip. or ≤30 yrs vs. >30 yrs)		0.26	0.85	0.13
Use of oral contraceptives^c
Never	241	128	4213	108
Ex, >25 years at start	64	137	4236	114
Ex, ≤25 years at start	20	113	4109	98
P		0.09	0.69	0.09

^a Adjusted for age, BMI, and physical activity.
^b Women who reportedly stopped bleeding, but had undergone a hysterectomy without double oophorectomy and an age at specimen collection <55 years were assigned an undetermined menopausal status.
^c Only a single woman reported current use of oral contraceptives. She was excluded from the analysis.