Adam was born five minutes after his twin sister and sadly he was born
deaf. That did not stop him excelling as a student; when I first met him as
a high school senior at age 17 he had just been accepted to a prestigious
college in the Northeast.
Adams father was 6'3" and his sister 5'7" - Adam
It is shameful that no attention had been paid to his obvious short
stature and delayed development during all of his pediatric care. It was his
sister, not his parents, who eventually went with him to one of the doctor
visits and insisted that something had to be done. (Whatever happened to
routinely plotting height and weight on growth curves?)
His bone age was delayed by 2.5 to 3 years and he failed to respond to
provocative testing for growth hormone. Not only was he short, but he had no
evidence of puberty and physical examination revealed only one small testis in
the scrotum. The second testis was found on ultrasound, but the urologist was
unable to relocate it to the scrotum so it was removed.
After discussion Adam elected to complete at least one year of GH
replacement therapy before beginning testosterone therapy, and he has grown
almost 4 in. He continues on GH and testosterone therapy has been started.
At college he remains a straight-A student.
Jeff provides a different story. By age 8 years, his parents were concerned
about his growth, which had been steady just above the 25th
percentile for height and weight. He was an only child; his father was
511; and mother was 56. Because of his short stature
relative to his parents, his pediatrician was able to prescribe GH replacement
without provocative testing but over the next two years he did not grow at all
and was falling off the growth curve. Subsequent testing confirmed that he had
Laron syndrome - GH insensitivity.
This autosomal recessive disorder is due to an abnormality in the GH
receptor, such that there is normal production of GH but failure to generate
insulin-like growth factor-I and its IGFBP3. As with Jeff, GH replacement is ineffective. Mecasermin
(Increlex) is a recombinant human IGF-I that is FDA approved as a treatment for
this genetic disorder.
Why am I, an endocrinologist who infrequently cares for pediatric
patients, involved with this uncommon pediatric problem? The pediatric
endocrinologist caring for Jeff thought that it would be wise to monitor his
BMD as well as his growth and growth velocity.
What should be monitored? There are conflicting opinions on this but my
bias is to monitor total bone mass and not regional BMD. The total body
approach also provides valuable information about body fat and lean mass which
are important to monitor in this case. Moreover it would be difficult, if not
near impossible, to decide which age group to use as the reference population if
one were to focus on spine or hip T-scores. Finally, as Jeffs bone size
is likely to increase in advance of bone mass, serial monitoring of regional
(2-D) BMD is likely to result in misleading serial data.