The objective of this study is to investigate the impact of hormones on lung disease in Cystic Fibrosis (CF) patients. Due to improved therapies, CF patients are living longer and healthier lives than they did 20 years ago. However, females have been shown to have a survival disadvantage. The median life expectancy is 33 in women and 37 in men with CF. The hypothesis is that estrogen and/or progesterone negatively impact lung health in CF. Therefore, understanding the impact of sex hormones (including the use of birth control pills) on the disease process is increasingly important. The purpose of this study is to determine if lung function, respiratory symptoms, or various markers of lung health change during different phases of the natural ovulatory cycle in order to understand if estrogen or progesterone hormones are impacting the disease relative to fluctuations in men with stable testosterone levels. The research objectives of this project are to:

• Determine if lung function, respiratory symptoms, or various markers of lung health change during different hormonal phases of the ovulatory cycle in women.
• Determine if men change lung function, respiratory symptoms, or various markers of lung health over time.
• Determine if oral contraceptive pills in women stabilize fluctuations in symptoms and improve lung health.

Inclusion Criteria:

• Male and female cystic fibrosis patients
• Must be greater than or equal to 18 years of age.
• All subjects must understand and sign the informed consent.
• Subjects must have the ability to read and write in English.
• Female subjects starting this study must be willing to use a double barrier method of birth control (such as condom or diaphragm) used with a spermicide (a substance that kills sperm), while participating in the study.

Exclusion Criteria for Main Study:

• Women who are pregnant, breast feeding, or who have had an oophorectomy.
• Women who have received a hormone contraceptive injection (such as Depo Provera) within the last 3 months.

Exclusion Criteria for Substudy:

• Men
• Women who have a history of breast cancer, abnormal vaginal bleeding, liver disease, coronary artery disease, cerebrovascular disease, uncontrolled hypertension, diabetes mellitus with vascular disease, or have had a stroke, heart attack, or blood clot within the past year, due to a possible reaction to Loestrin.
• Women who currently smoke cigarettes, due to the increased risk of serious cardiovascular events with Loestrin use.