title: Are adult patients with Laron syndrome osteopenic? A comparison between dual-energy X-ray absorptiometry and volumetric bone densities.
abstract: Severe short stature resulting from a deficiency in IGF-I is a prominent feature of Laron syndrome (LS). Although low bone mineral density (BMD) has been noted in LS patients examined by dual energy x-ray absorptiometry (DEXA), this technique does not take volume into account and may therefore underestimate the true bone density in patients with small bones. The aim of the present study was to evaluate the BMD yielded by DEXA in our LS patients using estimated volumetric values. Volumetric density was calculated with the following formulas: bone mineral apparent density (BMAD) = bone mineral content (BMC)/(area)(3/2) for the lumbar spine and BMAD = BMC/area(2) for the femoral neck. The study sample included 12 patients (mean age, 43.9 yr; mean height, 123.7 cm). Findings were compared with 10 osteopenic subjects without developmental abnormalities (mean age, 56 yr; mean height, 164.8 cm) and 10 healthy control subjects matched for sex and age to the LS patients (mean height, 165.5 cm). BMAD in the LS group was 0.201 +/- 0.02 g/cm(3) at the lumbar spine and 0.201 +/- 0.04 g/cm(3) at the femoral neck; corresponding values for the osteopenic group were 0.130 +/- 0.01 and 0.140 +/- 0.01 g/cm(3), and for the controls, 0.178 +/- 0.03 and 0.192 +/- 0.02 g/cm(3). Although areal BMD was significantly lower in the LS and osteopenic subjects compared with controls (P < 0.02) at both the lumbar spine and femoral neck, BMAD was low (P < 0.01) in the osteopenic group only. In conclusion, DEXA does not seem to be a reliable measure of osteoporosis in patients with LS.
authors.affiliation: Endocrine Institute, Rabin Medical Center, Beilinson Campus, Petah Tikva 49100, Israel. carlosb@netvision.net.il
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Benbassat
authors.forename: Varda
authors.initials: V
authors.lastname: Eshed
authors.forename: Moshe
authors.initials: M
authors.lastname: Kamjin
authors.forename: Zvi
authors.initials: Z
authors.lastname: Laron
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D015519:Bone Density; D001851:Bone Diseases, Metabolic / Q000000981:diagnostic imaging*; D005260:Female; D005272:Femur Neck / Q000000981:diagnostic imaging; D006130:Growth Disorders / Q000000981:diagnostic imaging*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000172:deficiency*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged
chemical_list: D007334:Insulin-Like Growth Factor I