Could you please explain the relationship between the Tanner stages and the bone age x-ray? My son is going through an early puberty. He is currently 10.9 years. We took him to a pediatric endocronoligist for evaluation four months ago and he was well into Tanner stage 4. The Dr. said that although his bone age was approx. 19 months advanced, he still had plenty of growth room and should reach a height of 5"11". We were very happy to hear this, but are confused because we had read that if a child went through the Tanner stages too early their growth could stop. He had a growth spurt last year and has grown a little over an inch in the last 3 months to almost 5'4". Are the bone age results what is important?

The Tanner stages assess genital and pubic hair development from Tanner Stage I which is none (prepubertal) to Tanner Stage 5 which is adult. These are actually based on photographs that Dr. Tanner, an English endocrinologist, took of a large number of children as they passed through puberty. The bone age is an X-ray of the left wrist which depicts the epiphyses (growth plates) of the bones The physician tries to estimate how much "growing room" remains in the growth plates by comparing the patient's bone age Xray to the Xray pictures in the Gruelich and Pyle Atlas. Usually, (but not always!), the two are roughly equivalent, that is, Tanner stage III usually occurs at about age 13, and Tanner Stage 4 at about age 14. While the bone age is a reasonable predictor of final adult height (plus of minus two inches), bone ages may change rapidly over a short period of time, thus altering the final height prediction. Unfortunately, human biology is not always reliably predictable, so the best guide will be obtained from careful continued observation of your son's growth pattern and pubertal development (especially testicular size) with periodic repeat bone age Xrays. Frank B. Diamond Jr M.D.

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