Androgenetic Alopecia with Normal Investigations
Yes, cases presenting with pattern hair loss and normal investigations (including normal androgen levels, normal ovulatory function, and no signs of hyperandrogenism) are appropriately diagnosed as androgenetic alopecia (AGA), not idiopathic androgenic alopecia. This is a distinct clinical entity from alopecia areata or other forms of hair loss.
Understanding the Diagnosis
Androgenetic alopecia is fundamentally a genetic condition that does not require elevated serum androgens for diagnosis. The pathogenesis involves:
- Genetic predisposition coupled with normal circulating androgens acting on genetically susceptible hair follicles 1
- Polygenic inheritance pattern affecting both men and women equally in incidence 2
- Local tissue sensitivity to androgens rather than systemic hyperandrogenism 2
Clinical Diagnostic Criteria
The diagnosis of AGA in women is established by clinical pattern recognition, not hormonal abnormalities:
- Pattern of hair loss: Increased thinning over frontal/parietal scalp with retention of frontal hairline and greater density over occipital scalp 2
- Age of onset: Typically begins between ages 12-40 years 2
- Presence of miniaturized hairs on examination 2
- Progressive nature following a defined pattern 3
When Hormonal Testing is NOT Required
Most women with AGA have normal menses, normal pregnancies, and normal androgen levels 2. Extensive hormonal testing is unnecessary unless specific signs of androgen excess are present:
- Hirsutism 2, 4
- Severe unresponsive cystic acne 2
- Virilization 2, 4
- Galactorrhea 2
- Oligomenorrhea or amenorrhea 5
- Clitoromegaly 5
Key Pathophysiologic Distinction
The critical mechanism is increased local androgen sensitivity in hair follicles, not systemic hyperandrogenism:
- Women with AGA have higher levels of 5-alpha reductase and androgen receptors in frontal hair follicles compared to occipital follicles 2
- Women also have much higher levels of cytochrome p-450 aromatase in frontal follicles than men, which partially protects against more severe baldness 2
- Dihydrotestosterone binds to androgen receptors in susceptible follicles, causing gradual miniaturization even with normal serum androgen levels 2
Important Clinical Pitfall
Do not confuse this with "idiopathic hirsutism" or assume all androgenic manifestations require elevated androgens. Recent evidence suggests that even conditions labeled "idiopathic" may involve relative hyperandrogenemia (androgens in upper normal range) or increased local androgen production at the tissue level 6. However, for androgenetic alopecia specifically, the diagnosis is clinical and does not require any hormonal abnormality.
Differential Diagnosis to Exclude
When normal investigations are present, ensure you have ruled out:
- Alopecia areata: Look for exclamation mark hairs, round yellow dots on dermoscopy, and patchy rather than patterned loss 7
- Telogen effluvium: Diffuse shedding without miniaturization pattern 7
- Trichotillomania: Incomplete hair loss with firmly anchored broken hairs 7
- Early scarring alopecia: May require biopsy if uncertain 7
Terminology Clarification
The term "idiopathic androgenic alopecia" is not standard nomenclature. The correct diagnosis is simply "androgenetic alopecia" (also called female pattern hair loss in women or male pattern baldness in men) 1, 2, 3. The condition is not idiopathic—the cause is known (genetic predisposition with androgen-dependent follicular miniaturization)—even though serum androgens may be normal.