5 Alpha Reductase by Ray Sahelian, M.D. 5 Alpha Reductase Inhibitor information

The enzyme 5 alpha-reductase (5 alpha R) catalyses the reduction of testosterone (T) into the more potent androgen dihydrotestosterone (DHT). The abnormal production of DHT is associated with pathologies of the main target organs of this hormone: the prostate and the skin. Benign prostatic hyperplasia (BPH), prostate cancer, acne, androgenetic alopecia in men, and hirsutism in women appear related to excess DHT production. Two isozymes of 5 alpha-reductase have been cloned, expressed and characterized (5 alpha R-1 and 5 alpha R-2). They share a poor homology, have different chromosomal localization, enzyme kinetic parameters, and tissue expression patterns. Since 5 alpha R-1 and 5 alpha R-2 are differently distributed in the androgen target organs, a different involvement of the two isozymes in the pathogenesis of prostate and skin disorders can be expected.

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Natural substances and herbs that have 5-alpha-reductase inhibitory activity
There are a number of substances in herbs that have 5-alpha-reductase inhibitory activity, however at this time we don't know how potent they are and how they compare to the active drugs finasteride and dutasteride. Here I will list a few and will add to the list over time.
Black cohosh extract has potential, see study below.

Saw palmetto, also known as serenoa repens, is being studied to determine how potent it is in terms of being a 5alpha-reductase inhibitor. Saw-Palmetto is found in Prostate Power Rx.

Willow herb has a substance called oenothein B, which appears to have 5-alpha-reductase inhibitory activity. For more oenothein information.
 

Black Cohosh and 5alphareductase
Inhibition of 5alpha-reductase in the rat prostate by Cimicifuga racemosa black cohosh.
Maturitas. 2006 Nov 1;55 Suppl 1:S75-82.  Department of Clinical and Experimental Endocrinology, University of Goettingen, Robert-Koch-Strasse 40, D-37075 Gottingen, Germany.
Prostate cancers and many thereof derived cell lines, as the LNCaP cells, grow androgen-dependent. In vivo testosterone is locally converted by 5alpha-reductase to 5alpha-dihydrotestosterone (5alpha-DHT) which is the major androgenic principle in prostates and seminal vesicles. The occurrence of prostate cancer and growth of LNCaP cells can be effectively inhibited by finasteride, a synthetic 5alpha-reductase inhibitor and by a black cohosh (Cimicifuga racemosa) extract. In the present contribution we tested whether the aqueous / ethanolic black cohosh extract BNO 1055 contains 5alpha-reductase inhibitors. Taken together, these results indicate that the black cohosh extract BNO 1055 contains one or more potent 5alpha-reductase inhibitors which may make this extract suitable for the prevention and treatment of prostate cancer and possibly of benign prostate hyperplasia (BPH).

Saw palmetto herb and 5alphareductase
Serenoa repens (Permixon, saw palmetto) inhibits the 5alpha-reductase activity of human prostate cancer cell lines without interfering with PSA expression.
Int J Cancer. 2005 Mar 20;114(2):190-4. Habib FK, Ross M, Ho CK, Lyons V, Chapman K. Prostate Research Group, University of Edinburgh, School of Molecular and Clinical Medicine, 2nd Floor Main Outpatient Building, Western General Hospital, Edinburgh EH2 2XU, Scotland, UK.
The phytotherapeutic agent Serenoa repens is an effective dual inhibitor of 5alpha-reductase isoenzyme activity in the prostate. Unlike other 5alpha-reductase inhibitors, Serenoa repens induces its effects without interfering with the cellular capacity to secrete PSA. Our results demonstrate that despite Serenoa repens effective inhibition of 5alpha-reductase activity in the prostate, it did not suppress PSA secretion. Therefore, we confirm the therapeutic advantage of Serenoa repens over other 5alpha-reductase inhibitors as treatment with the phytotherapeutic agent will permit the continuous use of PSA measurements as a useful biomarker for prostate cancer screening and for evaluating tumour progression.

5 Alpha Reductase Inhibitors and BPH

By inhibiting the production of dihydrotestosterone (DHT) locally within the prostate gland, 5alpha-reductase inhibitors have the effect of reducing prostate volume, improving lower urinary tract symptoms, increasing peak urinary flow, and decreasing the risk of acute urinary retention and need for surgical intervention. The combination of a 5alpha-reductase inhibitor and a alpha1-adrenergic antagonist significantly reduces the clinical progression of BPH over either drug class alone.

5 Alpha Reductase Inhibitors

The two 5alpha-reductase inhibitors currently available in pharmacies are finasteride and dutasteride. Finasteride is a 5alpha-reductase inhibitor approved for the treatment of male pattern hair loss. Originally approved for the treatment of benign prostatic hypertrophy in 1992, its approval was expanded in 1997 to include the treatment of androgenetic alopecia in men at a dose of 1 mg/day. Finasteride inhibits 5alpha-reductase, thereby prohibiting the conversion of testosterone to dihydrotestosterone (DHT), which is implicated in the development of hairless in some men.

The importance of dual 5alpha-reductase inhibition in the treatment of male pattern hair loss: results of a randomized placebo-controlled study of dutasteride versus finasteride.
J Am Acad Dermatol. 2006 Dec;55(6):1014-23. Olsen EA, Hordinsky M, Whiting D, Stough D, Hobbs S, Ellis ML, Wilson T, Rittmaster RS; Dutasteride Alopecia Research Team. Duke University Medical Center, Durham, North Carolina, USA.
Male pattern hair loss is a potentially reversible condition in which dihydrotestosterone is an important etiologic factor. Our aim was to evaluate the efficacy of the type 1 and 2 5alpha-reductase inhibitor dutasteride in men with male pattern hair loss. Four hundred sixteen men, 21 to 45 years old, were randomized to receive dutasteride 0.05, 0.1, 0.5 or 2.5 mg, finasteride 5 mg, or placebo daily for 24 weeks. Dutasteride increased target area hair count versus placebo in a dose-dependent fashion and dutasteride 2.5 mg was superior to finasteride at 12 and 24 weeks. Scalp and serum dihydrotestosterone levels decreased, and testosterone levels increased, in a dose-dependent fashion with dutasteride. Dutasteride increases scalp hair growth in men with male pattern hair loss. Type 1 and type 2 5alpha-reductase may be important in the pathogenesis and treatment of male pattern hair loss.

Side effects of 5 Alpha Reductase Inhibitors

The 5alpha-reductase inhibitors, finasteride and dutasteride, are associated with erectile dysfunction (ED), ejaculatory dysfunction (EjD) and decreased libido.

5alpha-reductase deficiency in male pseudohermaphrodites

Male pseudohermaphroditism involves 5alpha-reductase deficiency. This is an autosomal recessive form of partial male pseudohermaphroditism where there is a deficiency of the type 2 form of the enzyme 5 alpha-reductase.

Hirsute Women and 5alpha-reductase

Hirsute women often have increased activity of 5alpha-reductase, the enzyme that converts the androgen testosterone to its active metabolite, in hair follicles.

5 alpha nature nurture reductase
5 alpha female male reductase

5alphareductase, acne and alopecia in women
Effect of finasteride 5 mg (Proscar) on acne and alopecia in female patients with normal serum levels of free testosterone.
Gynecol Endocrinol. 2007 Mar;23(3):142-5.
In some women with acne or alopecia who have normal serum levels of free testosterone, no clinical improvement can be reached by the classical treatment with antiandrogens, isotretinoids or corticosteroids. Our hypothesis is that some of these women have an excessive activity of the enzyme 5alpha-reductase. We evaluated the subjective benefit of the treatment with finasteride (5 mg/day) in women with normal serum levels of free testosterone suffering from acne or alopecia. Nine of the 12 patients benefited from the finasteride treatment, their symptoms decreased significantly and they felt better psychologically than before the administration of finasteride. The other three patients did not benefit at all from finasteride and reported no change in the extent of the acne or alopecia. Treatment was generally well tolerated, only a few adverse effects were noted. Conclusions. Nine of the 12 patients benefited from the finasteride treatment. This supports our hypothesis of an excessive activity of 5alpha-reductase enzyme in peripheral tissue in these patients. The fact that three of the patients did not realize any change in their symptom severity implies that there must also be other pathways in the genesis of acne and alopecia in women with normal levels of free testosterone.