Blood Results Assessment for Functional Hypothalamic Amenorrhea
Direct Answer
Yes, these blood results are highly consistent with Functional Hypothalamic Amenorrhea (FHA) as the diagnosis for this woman's menstrual irregularities, particularly given the clear precipitating history of heavy fasting and calorie restriction following oral contraceptive discontinuation. 1
Key Diagnostic Features Supporting FHA
Gonadotropin Pattern (Most Diagnostic)
- LH 4.8 IU/L and FSH 4.7 IU/L are both low-normal, which is the hallmark laboratory finding in FHA 1
- The LH:FSH ratio is approximately 1.0, which effectively rules out PCOS (where LH:FSH ratio >2 is typical) 2, 3
- FHA is characterized by functional reduction in GnRH pulsatile secretion leading to decreased LH pulses and reduced serum LH and FSH levels 1
Estrogen Status
- Oestradiol of 69 pmol/L (approximately 18.8 pg/ml) on Day 1 of cycle is low, indicating hypoestrogenism 1
- This low estradiol is consistent with FHA, where patients reveal lower serum levels of oestradiol compared to PCOS patients 1
- The Endocrine Society notes that direct oestradiol assays are insensitive below 20 pg/ml, and this patient's level is just at that threshold 1
Androgen Profile (Rules Out PCOS)
- Total testosterone 0.5 nmol/L is normal-to-low, not elevated 1
- Free Androgen Index 0.4% is very low, excluding hyperandrogenism 1
- SHBG 118 nmol/L is elevated, which is characteristic of FHA rather than PCOS 1
- FHA patients have higher SHBG levels than PCOS patients because they lack the insulin resistance that suppresses hepatic SHBG synthesis 1
Metabolic Parameters
- HbA1c 36 mmol/mol is excellent, indicating normal insulin sensitivity 1
- FHA patients typically have low insulin levels and normal insulin sensitivity, contrasting with PCOS where insulin resistance is common 1
- Normal albumin 42 g/L suggests adequate protein status currently 4
Prolactin
Clinical Context Strongly Supports FHA
The history is pathognomonic for FHA:
- Heavy fasting and calorie restriction are classic precipitants of FHA 1, 2
- Energy availability below 30 kcal/kg FFM/day can inhibit LH pulsation and cause menstrual disorders 4
- Coming off oral contraceptives after 15 years unmasks the underlying hypothalamic suppression that was previously hidden by exogenous hormones 6
- The temporal relationship between caloric restriction and amenorrhea onset is diagnostic 1, 7
Critical Diagnostic Pitfall to Avoid
If this patient has polycystic ovarian morphology (PCOM) on ultrasound, do not misdiagnose her with PCOS 1, 2:
- Approximately 40-47% of women with FHA have PCOM (FHA-PCOM), which can be easily misclassified as PCOS phenotype D 1, 2, 3
- The key differentiators here are: clear history of energy deficit/caloric restriction, low-normal LH and FSH (not elevated LH:FSH ratio), very high SHBG (opposite of PCOS), and low androgens with very low Free Androgen Index 1
- FHA-PCOM requires correction of energy deficit as primary treatment, NOT PCOS-directed therapy 2, 3
What These Results Rule Out
- PCOS: Excluded by low-normal LH:FSH ratio, high SHBG, low androgens, and low Free Androgen Index 1
- Primary Ovarian Insufficiency: Excluded by low-normal (not elevated) FSH and LH 2, 5
- Hyperprolactinemia: Excluded by normal prolactin 2, 5
- Thyroid dysfunction: Would need TSH measurement, but not suggested by current presentation 2, 5
Immediate Clinical Implications
This patient requires urgent attention to bone health due to hypoestrogenism 2, 3, 5:
- Low estradiol levels put her at significant risk for decreased bone mineral density and osteoporosis 2, 3, 5
- The primary treatment is restoration of energy balance through increased caloric intake and reduction of any excessive exercise 4, 6, 8
- Energy availability should be increased above 30 kcal/kg FFM/day 4
- Body fat percentage above 22% may be required to restore menstrual function 4
- If menses do not resume after six months of lifestyle intervention, estrogen replacement therapy should be initiated to protect bone health 6, 8