I was on Lupron recently for endometriosis. After my fourth injection, I fell and got a compression fracture of the lumbar spine. Bone density testing showed I have the density of a 70-year-old. (I am 45.) Nobody seems to know what to do, other than calcium and vitamin D supplements, and probably Fosamax. The orthopedist is uncertain what could have caused such drastic bone loss. Serum calcium and phosphorus tests, as well as parathyroid panels, are all normal. I am five feet two inches, slight build, 110 pounds. I have always been active, exercise four to five times a week, and have never smoked. Is it possible than only four injections of Lupron could have caused that much bone loss?

M.B.

It is almost certain that your low bone calcium was a result of your condition before you ever began the Lupron therapy. I would guess you had a low level of body fat and -- like most women -- a low calcium intake. Blood calcium levels are not a factor in bone loss.

Lupron may certainly contribute to bone loss. The average woman on Lupron therapy will lose about 1-2 percent of bone calcium during the six-month course of therapy. The lost bone calcium is restored within a few months of stopping therapy. Most of this temporary loss can be prevented with add-back therapy, which involves adding a daily low dose of estrogen and progesterone at the start of therapy with Lupron. It is unfortunate that you were not placed on add-back therapy along with the Lupron. Even so, you would very likely have fractured whether or not you were on Lupron.

If a women plans to stay on Lupron for longer than six months with add-back therapy, I use a screening test called the urinary NTx test to check for bone loss. This is a simple urine test that measures a product of bone breakdown. If levels of NTx are high, that indicates that the rate of bone loss may be excessive. If excess bone loss is detected, then the add-back therapy dosage can be modified, or a bone-building drug such as Fosamax or Miacalcin may be added to restore bone calcium.