This guide is a work in progress which will be updated over time.
This complex body of research can be thought of in phases:
The development of finasteride by Merck was inspired by a 1974 paper reporting on individuals with atypical sexual development in a remote village of Dominican Republic. The paper, by Joanne Imperato-McGinley and colleagues, was titled ‘Steroid 5alpha-reductase deficiency in man: an inherited form of male pseudohermaphroditism’ (abstract). When these individuals matured, they did not have enlarged prostates and did not have recession of their hairline. The lack of expression of these typically male traits was attributed to a deficiency in the enzyme 5-alpha reductase. Finasteride was later developed to induce this deficiency in adults by inhibiting 5-alpha reductase.
Drug development and Proscar approval, 1981–1992
In the 1980s, inhibition of the 5-alpha reductase enzyme was explored in animal studies.
The Finasteride Study Group published an article on finasteride for the treatment of benign prostatic hyperplasia (BPH) in New England Journal of Medicine in 1992. Also in 1992, FDA approved Merck’s application for Proscar (finasteride, 5 mg/day) for the treatment of BPH.
Propecia development and approval, 1992–1997
In the mid-1990s, trials were run on finasteride for androgenetic alopecia culminating in FDA approval of Propecia (finasteride, 1 mg/day) in late 1997.
Whereas Proscar was used by urologists to treat men 50 and older, Propecia would be used by dermatologists to treat hair loss in much younger men, 18 and older.
Quiet period, 1998–2009
Following approval of Propecia, there was a slow trickle of papers, averaging seven or eight per year. During this period, finasteride was studied as a treatment to prevent prostate cancer. GSK developed another 5-alpha reductase inhibitor, dutasteride, which was approved as Avodart for the treatment of BPH.
Concerns about persistent adverse effects and ‘post-finasteride syndrome’, 2010–present
In 2010–2011, several papers raised concerns about adverse effects of finasteride, including those reported to continue after stopping the medication.
This period saw increased attention to adverse effects of finasteride as measured by papers per year, with nearly 50 papers published in 2020. Whereas earlier papers came from the fields of urology and dermatology, research during this period brought new perspectives including genetics, neuroendocrinology and epidemology.
Papers are grouped by symptom/presentation and field of study here.
Several systematic reviews and meta-analyses have been published in recent years.