A Junior Triathlete With a Healing Metatarsal, Amenorrhea, and a Race in Six Weeks
Alina is a 17-year-old nationally ranked junior triathlete training about 18 hours per week. She presents with 5 months of amenorrhea, a second metatarsal stress fracture in a walking boot, and two prior tibial stress reactions in the last 14 months. Height 168 cm, weight 51 kg (BMI 18.1), down 4 kg since last season. She describes eating 'clean' - mostly vegetables plus a protein shake - and routinely skips breakfast before morning swims. Resting HR 44, ferritin 12 ng/mL, vitamin D 22 ng/mL, TSH normal, hemoglobin normal. She wants to race the junior national qualifier in six weeks, asks whether she can keep swimming while the foot heals, and asks whether an oral contraceptive would 'fix the periods.'
1. State the unifying diagnosis in physiological terms and link the amenorrhea, the fractures, the low ferritin, and the bradycardia.
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Unifying diagnosis: low energy availability with relative energy deficiency in sport (RED-S), with a female-athlete-triad phenotype.
- Energy availability = dietary intake minus exercise energy expenditure, normalized to fat-free mass. Sustained intake below roughly 30 kcal/kg FFM triggers a coordinated downregulation.
- Reproductive axis: suppressed GnRH pulsatility → low LH/FSH → low estradiol → hypothalamic (functional) amenorrhea. This is an adaptive response to perceived scarcity, not a primary gynecologic disorder, and not a 'period problem.'
- Bone: low estradiol, low IGF-1, high cortisol, and low leptin shift remodeling toward resorption and suppress formation. Cortical bone at low-load sites (metatarsals, tibia) fails under repetitive load - hence recurrent stress injury at 17, which is the finding that matters most.
- Iron: low intake plus exercise-induced hepcidin elevation explains ferritin 12 despite normal hemoglobin; this impairs oxidative capacity and recovery.
- Bradycardia reflects high vagal tone from training volume compounded by chronic underfueling; it is not proof of fitness in this context.
The amenorrhea is not the disease. It is a marker that the bone and endocrine consequences are already present.
2. Give a prioritized management plan and address her two questions directly.
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Priorities, in order:
- Energy. Referral to a sports dietitian; add breakfast and carbohydrate around sessions; target a gradual weight gain toward a BMI consistent with her growth trajectory. This is the treatment, not an adjunct.
- Training load. Reduce total volume now. Permit swimming and cycling only if pain-free and only at reduced volume - cross-training that preserves the energy deficit is not treatment.
- Bone workup and micronutrients. DEXA is reasonable given prolonged amenorrhea plus multiple stress injuries; replete vitamin D; evaluate iron supplementation and repeat ferritin; review calcium intake.
- Screening. Screen for disordered eating and depression; involve her parents; clarify that weight and menses will be monitored.
- The race. She should not race in six weeks. Six weeks is not enough to restore energy status, and a metatarsal under race load in an underfueled athlete is a high-risk combination.
Her questions: An oral contraceptive will produce withdrawal bleeding and may improve bone density marginally at best; it does not restore energy availability, does not normalize IGF-1 or cortisol, and masks the one marker you are using to track recovery. It is not the answer here. Swimming: yes, if pain-free, at reduced volume, and only as part of a plan that increases intake - not as a way to maintain her current training load.
3. Define the criteria you would use to allow graded return to full training, and explain what you would monitor.
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Return criteria (all must be met, not any):
- Clinical and, where indicated, radiographic healing of the metatarsal; pain-free with walking, then hopping, then running.
- A demonstrated upward weight trajectory (roughly 0.5 kg/week) and reported intake adequate for training load - not just a promise to eat more.
- Restoration of regular menses is desirable but is not a gate; energy availability and weight trend are the operative variables. Waiting on menses alone delays care and rewards the wrong endpoint.
- Normalized ferritin and vitamin D, and resolution of any disordered-eating concerns.
Progression: walk-run in 10% weekly increments, then cycling and swimming at full volume, then sport-specific intensity, then racing. Any recurrence of bone pain means a step back and re-imaging.
Monitoring: monthly weight and training-load review, menstrual calendar, repeat ferritin and vitamin D, bone health follow-up, and psychological screening. Also address the systemic issue - coach and parents need to understand that a leaner athlete is not a faster athlete, and that her fracture history, not her race schedule, defines the timeline.