Effects of Letrozole on Precocious Puberty Due to McCune Albright Syndrome

Study Summary

This study will test the safety and effectiveness of letrozole in treating precocious (early) puberty in girls with McCune-Albright syndrome (MAS). The physical changes of puberty, such as breast enlargement, menstruation and growth spurt, as well as the emotional changes of this developmental stage, usually begin in girls between the ages of 8 and 14. Girls with MAS, however, often begin puberty before age 7. In MAS, large ovarian cysts produce high levels of estrogens (female hormones) that cause the changes of puberty. Children with MAS also have polyostotic fibrous dysplasia (PFD), a disease of bones that, depending on what parts of the skeleton are affected, can lead to broken bones or disfigurement of the head, face, arms and legs, or can cause pressure on nerves and blood vessels. Many children with MAS have cafe-au-lait spots (increased pigmentation) on areas of their skin as well. Letrozole is an estrogen-lowering drug that has been approved for treating women with breast and other cancers. Although the drug has not been tested or approved for use in children, some pediatric specialists have given it to girls with precocious puberty and MAS and found that it improves their condition without harmful side effects. This study will examine whether letrozole can lower estrogen in girls with MAS and arrest puberty. It will also study the drug's effects on substances involved in bone growth, including calcium, phosphate and amino acids. Girls 1 to 8 years old with MAS may be eligible for this study. Patients who were enrolled in NIH protocol 98-D-0145 (Screening and Natural History of Patients with Polyostotic Fibrous Dysplasia and the McCune-Albright syndrome) are also eligible. Participants will be admitted to the hospital for 2 to 3 days every 3 months for 15 months, for a total of 6 visits. They will undergo a complete history and physical examination and routine blood and urine tests every visit, as well as evaluations of their general health, growth and bo

Interventions

• DRUG Letrozole