Weight Gain Through Increased Energy Intake is the Primary Treatment
The answer is A (body fat). Increasing body fat through weight restoration is the definitive treatment for this adolescent with primary amenorrhea and BMI below the 5th percentile, as weight gain is the key intervention that leads to resumption of menses and prevents progressive bone loss. 1
Why Body Fat/Weight Gain is the Correct Answer
Weight restoration directly addresses the underlying pathophysiology of functional hypothalamic amenorrhea caused by energy deficiency. The Female Athlete Triad Coalition consensus establishes that normalizing body weight is the best strategy for successful resumption of menses and improved bone health. 1
Specific Weight Targets and Mechanisms
Weight gain of approximately 4-5 kg is typically required for menstrual resumption in amenorrheic adolescents with low BMI, with studies showing 75 amenorrheic women resumed menses after gaining an average of 4 kg. 1
The target should be gradual weight gain of 0.5 kg every 7-10 days, achieved through a 20-30% increase in caloric intake over baseline energy needs (approximately 200-600 kcal/day increase for someone consuming 2000 kcal/day). 1
Energy availability should reach at least 45 kcal/kg of fat-free mass to restore hormonal function and menstrual cyclicity. 1
Timeline for Recovery
Menstrual function can resume within several months of adequate energy intake and weight gain, though the exact timing varies based on severity and duration of energy deficiency. 1
Metabolic hormone profiles improve within days to weeks of increased energy availability, with body weight changes occurring over weeks to months. 1
Why the Other Options Are Incorrect
B. Exercise - Contraindicated in This Context
Exercise is NOT the answer and may actually worsen her condition. While weight-bearing exercise can improve bone density in healthy premenopausal women (1-3% improvement at lumbar spine), this benefit does not apply to severely underweight amenorrheic adolescents. 2
Estrogen may be permissive for osteogenic effects of mechanical loading, and chronically amenorrheic individuals show poor osteogenic benefits from exercise. 1
High-impact activity in females with low BMD may result in fractures rather than bone strengthening. 1
The primary issue is energy deficiency, not lack of mechanical loading—adding exercise without correcting the energy deficit would worsen the underlying problem. 1
C. Vitamins - Adjunctive Only, Not Primary Treatment
Vitamins alone will not restore menstrual function or correct the fundamental problem. While calcium and vitamin D status should be addressed as part of comprehensive care, supplementation without weight gain does not reverse amenorrhea or prevent continued bone loss. 1
Amenorrheic women lose approximately 2-3% of bone mass per year if the condition remains untreated, regardless of vitamin supplementation. 1
The etiology of bone loss includes both energy deficiency-related factors AND estrogen deficiency—vitamins address neither of these core mechanisms. 1
D. Sleep Hygiene - Not Relevant to Primary Pathology
Sleep hygiene has no established role in treating functional hypothalamic amenorrhea secondary to low body weight. The evidence clearly identifies energy deficiency as the causative factor, not sleep disturbance. 1
Critical Clinical Considerations
Monitoring Requirements
Weekly weight monitoring is recommended when initiating treatment, using the same scale with minimal clothing to ensure accuracy. 1
Track menstrual function as a marker of hypothalamic-pituitary-gonadal axis recovery, as resumption of regular menstruation indicates normalization of energy balance. 3
Common Pitfalls to Avoid
Do not prescribe oral contraceptives as primary treatment—one case study showed 2 years of oral contraceptives without weight gain resulted in no BMD improvement, while subsequent weight gain led to 25.5% increase in spinal BMD. 4
Individual weight targets matter—the weight required for menstrual resumption can be predicted by the weight at which menstruations ceased, and population-based targets may be too low. 5
Patients with higher premorbid BMI may require higher target weights for menstrual recovery. 6
Long-term Outcomes
Weight gain combined with menstrual resumption produces substantial bone health improvements: studies demonstrate lumbar spine BMD increases of 3.1% and hip BMD increases of 1.8% over one year in those who gain weight and resume menses, while those who don't recover menses show continued BMD decreases. 1