Body Composition by DXA in Patients with Klinefelter and Kallmann Syndrome: The Kama Study.

Patients with Kallmann syndrome had significantly higher appendicular lean mass index (ALMI) values than those with Klinefelter syndrome.

• ALMI was 8.37 ± 1.15 kg/m² in Kallmann syndrome vs 7.28 ± 1.20 kg/m² in Klinefelter syndrome (P < .001)
• Study included 50 patients total: 29 with Klinefelter syndrome and 21 with Kallmann syndrome
• All patients were receiving testosterone replacement therapy at the time of assessment
• Body composition was evaluated using whole-body dual-energy x-ray absorptiometry (DXA)

FSH levels were inversely associated with ALMI in univariable analysis, and this association remained significant after adjustment for confounders.

• Univariable analysis: B = -0.026; P = .002
• After adjustment for confounders: B = -0.030; P = .0022
• The two syndromes differ in gonadotrophin profiles despite both being characterized by reduced testosterone levels
• This finding supports a potential role for FSH in modulating muscle mass independently of testosterone levels

Radiologic sarcopenic obesity was identified in 14% of the overall study population, with the majority occurring in patients with Klinefelter syndrome.

• 7 out of 50 patients (14%) had radiologic sarcopenic obesity
• 6 of the 7 cases were in Klinefelter syndrome patients (6/29) and 1 was in a Kallmann syndrome patient (1/21)
• Osteosarcopenic obesity was found in 2 patients (4%), both with Klinefelter syndrome
• This is a single-center, retrospective observational study

Klinefelter syndrome and Kallmann syndrome are two rare genetic disorders that both involve reduced testosterone levels but differ in their gonadotrophin profiles.

• No prior studies have directly compared body composition in these two syndromes
• The study assessed prevalence of altered body composition parameters including ALM, total body fat (TBF), visceral adipose tissue (VAT), ALMI, and ALM-to-weight ratio
• Secondary objectives included evaluating associations between body composition, bone mineral density (BMD), and serum FSH levels
• Klinefelter syndrome is associated with elevated FSH, while Kallmann syndrome is associated with low FSH due to gonadotrophin deficiency