SAT-802 Severe Male Osteoporosis from Relative Energy Deficiency Syndrome in Sport

Abstract Disclosure: I.K. Smith: None. Background: Relative Energy Deficiency in Sport (previously referred to as the Female Athlete Triad) is less defined and likely under recognised in Males due to the absence of amenorrhoea as a defining feature. Clinical case: A 39-year-old male recreational runner (running 120kms/week) presented with multiple stress fractures including the left iliac crest, calcaneal, left and right fibular fracture and bone marrow oedema in right pubic body. Fractures occurred within a four-year period and prior to this his only fracture history was a distal radius from a fall on an outstretched hand as a child. Bone density scan revealed very low bone density with a lumbar spine Z-score of - 3.8, T-score - 3.9 and left femoral neck Z-score of - 2.1 and T-score - 2.6. There was no significant medical or family history and he was not on any regular medications. Clinical examination revealed a lean Caucasian male with no obvious syndromic features. He had a moderate chest pectus carinatum. Clothed weight was 64.0kg, height 182cm and BMI 19.3kg/m2. Initial review recommended referral to a sports dietitian and increase in caloric intake. Osteoporosis screen was completed after nutritional changes and commencement of calcium and vitamin D supplementation. Pathology revealed negative coeliac serology, normal serum calcium, PTH, vitamin D of 108nmol/L (50-200). TSH, IGF-1 and growth hormone were all within normal reference range. The 24-hour urine calcium, cortisol and 1-Methyl histamine were also all within normal limits. Testosterone was low-normal at 10.8nmol/L (8.3-29) with normal gonadotropins LH 3.1IU/L (<10) and FSH 9.0IU/L (<10). There was a low calculated free testosterone at 182.6pmol/L (255.0-725.0) with normal sex hormone binding globulin of 41nmol/L (11-71). Karyotype analysis was a normal male XY. He was iron deficient with a ferritin of 14ug/L (30-300). The patient was diagnosed with prolonged relative energy deficiency syndrome characterised by mild hypogonadism, iron deficiency and bone density in the lumbar spine 3.8 standard deviations below average for his age and sex. Bone turnover markers were tested after increased caloric intake and decreased running volume. There was increased bone formation compared to resorption with a P1NP of 100ug/L (15-80), compared to a CTX of 464ng/L (100-600). Due to ongoing P1NP elevation, pharmacotherapy was not initiated. Lifestyle management with increased caloric intake, weight gain and decrease in total physical activity was recommended. Conclusion: This case is an example of significantly reduced bone density due to unintentional relative energy deficiency. Relative energy deficiency in endurance athletes is an important yet under recognised cause of osteoporosis in males and treatment is predominantly lifestyle related. Presentation: Saturday, July 12, 2025