This study will include cystic fibrosis patients who are greater or equal to 18 years of age. a total of 60 subjects may be consented at uTSW or Children's Medical Center. These subjects must understand and sign informed consent. Women Women who are taking hormone contraceptives when consented will complete a 2 month wash out of their hormone contraceptive. all women will be followed for one menstrual cycle observationally off of any hormone supplementation. They will have 3 study visits corresponding to their menstrual cycle phases (menses, ovulation, and luteal). Women participating in the main study may participate in the optional sub-study. Following a negative urine pregnancy test, women will be started on once daily oral Loestrin (1.5 mg norethindrone + 0.03 mg ethyl estradiol). They will be followed for two months on this agent and have 2 additional study visits. Men Men participating in this study will be followed for 1 day observationally. They will have 1 study visit. The estimated time for completion of this project is 4 years. it will take 2-3 years to identify, consent subjects, and to collect pertinent data. it will take one more year to analyze the data and write appropriate manuscripts.
* 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.