Endocrine Abstracts

Background: Testosterone therapy is recommended for the management of puberty in Duchenne muscular dystrophy (DMD) from 12 years, according to the 2018 international standards of care with studies demonstrating improvement in linear growth. The majority become non-ambulant during mid-to-late adolescence. Accurately measuring height in non-ambulant adolescent boys can be challenging compounded by lower limb contractures. Estimated height from segmental body part measurements often overestimates actual height.

Objectives: The aim of this study was to retrospectively evaluate the efficacy of 12 months of testosterone on bone growth in boys with DMD using metacarpophalangeal length measured on radiographs.

Methods: A single observer measured the 19 tubular bones of the hand using the digital ruler on the radiology platform. Raw bone length measurements were converted into Z-scores from published paediatric normative data. To summarise the data for each patient, mean of the Z-scores for the 19 bones was calculated, referred to as the ‘composite bone length Z-score.’ Descriptive data are expressed as median(IQR).

Results: Median age at baseline was 14.3 years(IQR 1.3). All boys were pre-pubertal, with a median bone age delay of 2.9 years. All were receiving daily glucocorticoid therapy. Injectable testosterone was administered to 7 boys, while 7 received topical therapy. At baseline, 8/14 boys(57%) were non-ambulant, and was 9/14(64%) at 12 months. At 12 months, 13 boys were in early puberty(G2-G3), and one boy was in late puberty(G4). At baseline, all median bone-length Z-scores were significantly lower than zero(P<0.05). After 12 months of testosterone, all bone-length Z-scores, except for distal phalanx 5, remained significantly lower than baseline. The median composite bone-length Z-score was −2.6(IQR 1.9) at baseline, and this decreased to −3.5(IQR 2.3) at 12 months(P<0.05). The median rate of composite bone growth increased from 0.2 mm/year prior to testosterone to 0.6 mm/year – a median increase of 238%.

Conclusion: Using the metacarpophalangeal length, bone growth rate increased by over 200% after one year of testosterone. This improvement in growth rate is insufficient to achieve complete catch-up, possibly indicating the presence of growth hormone resistance due to long-term glucocorticoid