Table III.
Summary of key findings of the meta-analysis on the effect of COCs on total T, free T and SHBG concentrations with the comparison no COC (pretreatment) versus COC (end of treatment).
| Type of analysis | Number of studies | Number of treatment groups | Number of subjects Total (no COC versus COC) | MD [95% CI] | P value | Heterogeneity (I2) (%) |
|---|---|---|---|---|---|---|
| COC effect on total T [nmol/l] | 39 | 64 | 2741 (1405 versus 1336) | −0.49 [−0.55, −0.43] | <0.001 | 55 |
| Subgroup: type of progestin | 39 | 61 | 2452 (1256 versus 1196) | −0.50 [−0.56, −0.43] | 0.20 | 34.7 |
| First generation (estranes) | 8 | 313 (159 versus 154) | −0.33 [−0.50, −0.17] | |||
| Second generation (gonanes) | 21 | 934 (474 versus 460) | −0.54 [−0.63, −0.45] | |||
| Third generation (gonanes) | 28 | 1044 (542 versus 502) | −0.51 [−0.62, −0.40] | |||
| Fourth or unclassified generation | 4 | 161 (81 versus 80) | −0.52 [−0.77, −0.27] | |||
| COC effect on SHBG [nmol/l] | 39 | 67 | 2917 (1487 versus 1430) | 99.10 [86.44, 111.75] | <0.001 | 96 |
| Subgroup: type of progestin | 38 | 64 | 2628 (1338 versus 1290) | 103.09 [89.51, 116.66] | <0.001 | 97.8 |
| First generation (estranes) | 9 | 347 (176 versus 171) | 89.06 [65.94, 112.19] | |||
| Second generation (gonanes) | 20 | 934 (470 versus 464) | 35.84 [26.86, 44.82] | |||
| Third generation (gonanes) | 28 | 1036 (536 versus 500) | 136.76 [120.66, 152.86] | |||
| Fourth or unclassified generation | 7 | 311 (156 versus 155) | 157.39 [111.62, 203.16] | |||
| [95% CI] | ||||||
| COC effect on free T (log scale; relative change) | 29 | 47 | 2043 (997 versus 1046) | 0.39 [0.35, 0.43] | <0.001 | 79 |
| Subgroup: type of progestin | 29 | 45 | 1865 (954 versus 911) | 0.38 [0.35, 0.42] | 0.32 | 12.0 |
| First generation (estranes) | 2 | 54 (27 versus 27) | 0.38 [0.31, 0.48] | |||
| Second generation (gonanes) | 13 | 596 (302 versus 294) | 0.42 [0.36, 0.50] | |||
| Third generation (gonanes) | 24 | 946 (490 versus 456) | 0.37 [0.32, 0.43] | |||
| Fourth or unclassified generation | 6 | 269 (135 versus 134) | 0.34 [0.25, 0.46] |
CI, confidence interval; COC, combined oral contraceptive; MD, mean difference; SHBG, sex hormone-binding globulin; T, testosterone.