Background: This study was conducted to examine the effect of oral contraceptives on endogenous reproductive hormone levels in order to assess the suitability of oral contraceptive users as experimental and/or control groups in human performance studies.
Study design: Ninety-five females who were taking a variety of oral contraceptives (2 types and 11 brands) were recruited. A single blood sample was analysed for endogenous concentrations of oestradiol and progesterone.
Results: There were significant differences (p<.05) in circulating oestradiol and progesterone as a result of oral contraceptive type and brand. Overall, oral contraceptive use resulted in low levels of oestradiol and progesterone and large variation in hormone concentration when multiple brands were analysed together.
Conclusion: This study indicates that future studies should employ a single pill type and brand when using oral contraceptive users as either a control or experimental group and that comparison between oral contraceptive users as a control group and the early follicular phase of the menstrual cycle as an experimental group should be reconsidered.
Keywords: Athletic performance; Control group; Estrogen; Experimental group; Progesterone.
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