Since the type of alopecia isn’t identified, I’ll approach the two most common forms: alopecia areata; and androgenetic alopecia.
Alopecia areata is a common form of localized hair loss. It may occur anywhere on the body, but the most typical presentation first appears as one or more round patches of baldness on the scalp. A diffuse pattern of hair loss is also possible. The etiology of alopecia areata appears to be immunologically-based. While it’s frequently idiopathic, some patients have an associated thyroid autoimmunity, or rarely a connective tissue disorder such as lupus. So, it would be valuable to check for these conditions. If found to be negative, then either topical or intralesional corticosteroids can be useful in reversing the alopecia.
In androgenetic alopecia (AGA), there’s progressive miniaturization of the hair shaft with successive anagen cycles. In males, there will be bitemporal recession, and thinning at the crown. There’s no apparent shedding of the hair. In this case, accelerated peripheral conversion of androgens is at fault. Oral finasteride, either alone or in combination with topical minoxidil are the treatments of choice. In cases of AGA, there’s no particular need for serological testing.
In cases where the pattern or onset makes it unclear, a scalp biopsy that’s mounted transversely can be instructive in identifying the etiology. This biopsy should be interpreted by a dermatopathologist who’s familiar with this form of biopsy procedure.