TOPLINE:

Among patients with Klinefelter and Kallmann syndromes on testosterone therapy, body composition was altered, and appendicular lean mass (ALM) differed between the groups. Follicle-stimulating hormone was associated with ALM, suggesting a potential independent role of this gonadotropin hormone in regulating muscle mass.

METHODOLOGY:

• This retrospective study assessed the prevalence of altered body composition parameters in patients with Klinefelter and Kallmann syndromes who were receiving testosterone replacement therapy and compared body composition between the two groups.
• A total of 50 Caucasian men were analysed — 29 with Klinefelter syndrome (median BMI, 24.4) and 21 with Kallmann syndrome (median BMI, 26.3); the median age was 41 years in both groups.
• Body composition was assessed using DEXA, which included ALM, total body fat, and visceral adipose tissue; the height-adjusted ALM index (ALMI) was calculated as ALM divided by height squared.
• DEXA was also used to assess bone mineral density at the lumbar spine, total hip, and femoral neck.
• Following an overnight fast, blood samples were obtained for hormonal assays.

TAKEAWAY:

• Overall, radiologic sarcopenic obesity occurred in 14% of patients (21% in the Klinefelter group and 5% in the Kallmann group), whereas osteosarcopenic obesity was present in 4% of patients, exclusively in the Klinefelter group.
• Patients with Kallmann syndrome had significantly higher ALMI values than those with Klinefelter syndrome (8.37 vs 7.28 kg/m²; P < .001), and this difference persisted after accounting for potential confounders.
• Higher levels of follicle-stimulating hormone were significantly associated with lower ALMI values after adjusting for potential confounders (P = .002).
• Bone mineral density did not differ significantly between the groups.

IN PRACTICE:

"In patients with these conditions, early lifestyle interventions — alongside pharmacological treatment — should be encouraged. A multidisciplinary approach incorporating muscle-strengthening exercise and nutritional support may offer added benefits for improving bone health in this population," the authors of the study wrote.

SOURCE:

This study was led by Caterina Buoso, SSD Endocrinologia, University of Brescia, Brescia, Italy. It was published online on October 10, 2025, in The Journal of Clinical Endocrinology & Metabolism.

LIMITATIONS:

This study was limited by the small sample size. The low number of patients with vertebral deformities potentially precluded the analysis of the relationship between body composition and the risk for fracture. This study lacked data on functional tests for sarcopenia.

DISCLOSURES:

This study did not receive any funding from public, commercial, or not-for-profit organisations, and the authors reported having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.