Assessment of FHA Diagnosis Based on Blood Work and History
Based on the available blood work and clinical history, there is nothing to suggest that FHA is the wrong diagnosis—in fact, all parameters strongly support FHA and effectively rule out alternative diagnoses, particularly PCOS. 1
Hormonal Profile Confirms FHA
The gonadotropin levels are characteristic of hypothalamic suppression:
- Low-normal LH (4.8 IU/L) and FSH (4.7 IU/L) are classic for FHA, reflecting suppressed GnRH pulsatility 1, 2
- The LH:FSH ratio of approximately 1.0 effectively rules out PCOS, where ratios typically exceed 2.0 1, 3
- Approximately 82% of FHA patients demonstrate an LH:FSH ratio <1, making this patient's ratio entirely consistent with FHA 3, 1
The estrogen status confirms hypoestrogenism:
- Low estradiol (69 pmol/L, approximately 19 pg/mL) indicates the hypoestrogenism characteristic of FHA 1
- This level is at the threshold where standard assays become unreliable, but the clinical picture is clear 3
Androgen and Metabolic Profile Excludes PCOS
The androgen parameters definitively exclude hyperandrogenism:
- Normal-to-low total testosterone (0.5 nmol/L) rules out PCOS 1
- Very low Free Androgen Index (0.4%) is incompatible with PCOS and strongly supports FHA 1
- Elevated SHBG (implied by the very low FAI) is characteristic of FHA patients, who have higher SHBG than PCOS patients 1, 3
Metabolic parameters support FHA over PCOS:
- Normal HbA1c (36 mmol/mol) indicates normal insulin sensitivity, typical of FHA 1
- FHA patients characteristically have low insulin levels and normal insulin sensitivity, contrasting sharply with PCOS where insulin resistance is common even in lean patients 3, 1
Clinical Context is Diagnostic
The history of heavy fasting and calorie restriction is a classic FHA precipitant:
- Energy deficit through caloric restriction is one of the three main causes of FHA (along with excessive exercise and psychological stress) 1, 4
- The temporal relationship between caloric restriction and amenorrhea onset is diagnostic of FHA 1
- This clear history of energy deficit is a key differentiator from PCOS 3, 1
Addressing the PCOM Concern
If polycystic ovarian morphology is present on ultrasound, this does NOT invalidate the FHA diagnosis:
- PCOM occurs in 41.9-48% of women with FHA, substantially higher than the 14-33% prevalence in the general population 3, 4
- FHA-PCOM is a recognized entity that can be easily misdiagnosed as PCOS if clinicians rely solely on Rotterdam criteria 3
The key differentiators between FHA-PCOM and PCOS are all present in this patient:
- Clear history of energy deficit/caloric restriction 3, 1
- Low-normal LH and FSH (not the elevated LH seen in PCOS) 1
- Very high SHBG reflected in the extremely low FAI 3, 1
- Low androgens with very low Free Androgen Index 1
- LH:FSH ratio of 1.0 (not >2 as in PCOS) 3, 1
What Would Contradict FHA
The following findings would suggest an alternative diagnosis, but NONE are present:
- LH:FSH ratio >2 would suggest PCOS (this patient has ratio of 1.0) 3, 1
- Elevated gonadotropins would indicate primary ovarian insufficiency (this patient has low-normal levels) 4
- Evidence of insulin resistance would favor PCOS (this patient has normal HbA1c) 3, 1
- Frank hyperandrogenism with elevated testosterone and FAI would suggest PCOS (this patient has low-normal testosterone and very low FAI) 1
- Low SHBG would favor PCOS over FHA (this patient has high SHBG based on the very low FAI) 3, 1
- Absence of typical FHA triggers would make the diagnosis questionable (this patient has clear history of caloric restriction) 3, 1
Critical Clinical Implications
This patient requires urgent attention to bone health:
- The hypoestrogenism puts her at significant risk for decreased bone mineral density and osteoporosis 3, 1
- Baseline DEXA scan is recommended for patients with at least 6 months of amenorrhea 3
- FHA carries a 2-fold increased fracture risk compared to healthy eumenorrheic women 3
Cardiovascular risk assessment is warranted: