Reply to Lipworth et al.: Sex Hormones and Asthma: Don’t Forget Progesterone

From the Authors:

We thank Dr. Brian Lipworth and colleagues for their interest in our recent cross-sectional study of sex steroid hormones and asthma among adult participants in the National Health and Nutrition Examination Survey (1). We showed that elevated serum levels of free testosterone were associated with lower odds of current asthma in women. After stratification by obesity, we found that elevated serum levels of both free testosterone and estradiol were associated with lower odds of current asthma in obese women and that an elevated serum estradiol level was associated with lower odds of current asthma in nonobese men (1).

Similar to estradiol, progesterone levels fluctuate according to the follicular phase of the menstrual cycle. As acknowledged in the Discussion of our study limitations, we had no information on such phases of the menstrual cycle. Moreover, serum progesterone was not measured in the National Health and Nutrition Examination Survey. We agree with Dr. Lipworth and colleagues that a potential role of progesterone should be examined in future longitudinal studies of sex hormones and asthma.