When you express interest in a specific study, the information from your profile will be sent to the doctor conducting that study. If you're eligible to participate, you may be contacted by a nurse or study coordinator.
If you select a health category rather than a specific study, doctors who have active studies in that area may contact you to ask if you would like to participate.
In both cases, you will be contacted by the preferred method (email or phone) that you specified in your profile.