ESPE Abstracts

Background: Testosterone therapy is recommended for management of puberty from the age of 12 years in boys with Duchenne Muscular Dystrophy(DMD) in accordance with the 2018 international standards of care. The majority of boys loose ambulation in mid to late adolescence. Height measurement is problematic in these adolescents s as lower limb contracture can be common and estimated height from segmental body part measurements generally over-estimate height.

Aims: To evaluate the efficacy of testosterone on bone growth in DMD by a retrospective evaluation using metacarpophalangeal index on hand radiographs.

Methods:The 19 tubular bones of the hand were measured by a single observer using the digital ruler on the radiology platform(PACS). Raw bone length measurements were converted to Z-scores based on published paediatric normative data. To produce a single summary descriptor for each patient, the mean of the z-scores for the 19 bones was calculated called the ‘composite bone length z-score’. Descriptive data is expressed as median(inter-quartile range).

Results: Median age at baseline was 14.3 years(1.3). All boys were pre-pubertal (G1, testicular volume<4 ml) with median bone age delay of 2.9 years(4.9). All boys were on daily glucocorticoid with median Prednisolone equivalent dose of 0.4(0.2) mg/kg and this was 0.3(0.3) mg/kg at 12 months of testosterone. At baseline, 8/14(57%) were non-ambulant, and this was seen in 9/14(64%) at 12 months of testosterone. At 12 months, 13 boys were in early puberty(G2-G3) and one boy was in late puberty(G4). At baseline, median bone length Z-scores(metacarpal 1-5; proximal phalanx 1-5; mid-phalanx 2-5; distal phalanx 1-5) were all significantly lower than zero[P<0.05]. Following 12 months of testosterone, all bone length Z scores other than distal phalanx 5 were significantly lower than baseline. At baseline, median composite bone length Z score for chronological age was -2.6(1.9) and this was -3.5(2.3) at 12 months[P< 0.05]. Median rate of composite bone growth was 0.2 mm/year prior to testosterone and this was increased to 0.6 mm/year which equates to a median increase of 238%(282).

Conclusion: Using the metacarpophalangeal index, rate of bone growth increased by over 200% after a year of testosterone therapy in boys with DMD. However, this improvement in growth rate is not sufficient to lead to complete catch-up growth which could reflect the state of growth hormone resistance with long term glucocorticoid therapy.