Table 2.
Characteristics of studies investigating BPA exposure and early pubertal outcomes.
| Study | Country | Study design | Sample (cases vs. controls) | BPA assessment method | Biological matrix | Pubertal outcome definition | BPA sample timing | BPA adjustment method | Outcome diagnosis window | Key findings | Adjusted covariates |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Kim et al. (22) | Korea | Case–control | 51 CPP vs. 52 controls | GC–MS | Serum | Central precocious puberty confirmed by clinical exam + GnRH stimulation | At time of clinical diagnosis | None (serum) | Age 7–9 yr | Geometric mean BPA significantly higher in CPP girls (6.5 vs. 3.4 ng/mL, p < 0.0001). Highest BPA tertile associated with markedly increased CPP risk (OR 7.68; 95% CI: 2.34–25.19). | Age, BMI; serum BPA measured at time of clinical diagnosis; quality-controlled GC–MS with internal standards |
| Durmaz et al. (23) | Turkey | Case–control | 28 ICPP vs. 25 controls | HPLC | Urine | Idiopathic CPP confirmed by GnRH stimulation | At diagnosis | Creatinine-adjusted | Age 4–8 yr | Median urinary BPA significantly higher in ICPP girls (8.34 vs. 1.62 μg/g Cr; OR 8.68; 95% CI: 2.03–32.72). | Age, BMI; creatinine-adjusted urinary BPA; urine collected at diagnosis; HPLC analytical quality control reported |
| Lee et al. (24) | Korea | Cross-sectional | 42 CPP, 40 PPP, 32 controls | Urinary BPA quantified with steroid metabolomics panel | Urine | Central and peripheral PP diagnosed clinically and hormonally | Single-time-point urine sampling | Not specified | Concurrent with outcome assessment | BPA correlated with alterations in steroidogenesis, but not clearly with onset of PP. | Not fully reported; single-time-point urine sampling; cross-sectional design limits temporality; exposure measured concurrently with outcome |
| Supornsilchai et al. (25) | Thailand | Cross sectional | 41 advanced puberty vs. 47 controls | UPLC–MS/MS | Urine | Advanced puberty (clinical + BA and hormonal evaluation) | At time of clinical evaluation | Creatinine-adjusted | At time of clinical evaluation | Median adjusted BPA significantly higher in advanced puberty (1.44 vs. 0.59 μg/g Cr, p < 0.05). | None (unadjusted); creatinine-adjusted urinary BPA; LC-based method with low limit of quantification reported; sampling at time of clinical evaluation |
| Jung et al. (26) | Korea | Multicenter case–control | 47 CPP vs. 47 controls | LC–MS/MS | Urine | Central precocious puberty | First-morning urine samples | Creatinine-adjusted | At diagnosis | No significant difference in urinary BPA between CPP and pubertal control group (0.63 vs. 1.7 μg/g Cr, p = 0.092). | BMI, age; first-morning urine samples; creatinine-adjusted BPA; multicenter recruitment reduces selection bias |
| Chen et al. (27) | China | Case–control | 136 ICPP vs. 136 matched controls | LC–MS/MS with internal quality control | Urine | CPP confirmed by GnRH stimulation + bone age criteria | At diagnosis | Creatinine-adjusted | Age 6–9 yr | Highest quartile of BPA associated with OR 9.08 (95% CI: 2.83–29.15). | Age, BMI, endocrine parameters; creatinine-adjusted BPA; internal quality control; exposure measured at diagnosis; matching on age and BMI |
| Mohsen et al. (28) | Egypt | Case control | 60 PP vs. 40 controls | HPLC | Urine | Idiopathic precocious puberty diagnosed clinically | At time of diagnosis | Not specified | At diagnosis | Mean urinary BPA markedly higher in PP group (405.02 vs. 97.95 μg/g Cr; p < 0.001). | Not clearly specified; urine sampling at time of diagnosis; cross-sectional exposure ascertainment within case–control framework |
| Durmaz et al. (29) | Turkey | Case–control | 25 premature thelarche vs. 25 controls | HPLC | Urine | Premature thelarche (< 8 years, breast stage ≥2) | At clinical presentation | Creatinine-adjusted | < 8 yr at diagnosis | Urinary BPA significantly higher in PT girls (3.2 vs. 1.62 μg/g Cr; p < 0.05). | Not specified; creatinine-adjusted urinary BPA; exposure measured at clinical presentation |
| Vu Huynh et al. (30) | Vietnam | Case–control | 124 PP vs. 126 controls | LC–MS/MS | Urine | Precocious puberty confirmed clinically and endocrinologically | At diagnosis | Not specified | Case–control temporal ordering | BPA detectable in 11.3% of PP cases and 0% of controls (p < 0.001), supporting a positive association. | Age, BMI; urinary BPA assessed at diagnosis; case–control temporal ordering remains observational |
CPP, central precocious puberty; PPP, peripheral precocious puberty; PT, premature thelarche; BA, bone age; GnRH, gonadotropin-releasing hormone; HPLC, high-performance liquid chromatography; LC–MS/MS, liquid chromatography–tandem mass spectrometry; UPLC–MS/MS, ultra-performance liquid chromatography–tandem mass spectrometry; GC–MS, gas chromatography–mass spectrometry; OR, odds ratio; CI, confidence interval.