If you are found to be eligible to take part in this study and you agree to take part, you will be randomly assigned (as in the toss of a coin) to 1 of 2 groups. There is an equal chance that you will be assigned to either group. One group (the 'Surgical' Group) will receive the parathyroid surgery and "observation" (the review of blood tests by the study doctor) during the course of the study. The other group (the 'Observation' Group) will receive observation alone, and then surgery after their study participation ends.