Does using finasteride increase the risk of diabetes?

Finasteride at 5 mg doses Linked to a Small Increased Risk of Type 2 Diabetes

Studies to date have had varied results as to whether finasteride leads to insulin resistance. In fact, some studies have suggested that inhibition of 5 alpha reductase could lead to insulin resistance whereas others have suggested it could lead to an improvement in insulin sensitivity. 

Finasteride at 1 mg is marketed under Propecia as well as generics and is used for treatment of male androgenetic alopecia (male balding). Finasteride at 5 mg is marketed under brand name Proscar (as well as generics) and is used for treatment of male prostate enlargement. 

2010 Study suggests 1 mg Finasteride improves Insulin Sensitivity

In 2010, Duskova and colleagues examined 12 men with premature balding who used Finasteride (1 mg/day) for 12 months. A hormonal profile and lipid spectrum were monitored after 4, 8 and 12 months of treatment and insulin tolerance tests were repeated after 12 months of the treatment. After treatment with finasteride the authors observed an initial increase in total cholesterol and HDL- and LDL-cholesterol, which stabilized with prolonged treatment. They found a significant decrease in glycated hemoglobin HbA1c and insulin resistance. 

In 2016, studies by Hazelhurt et al suggested that Dutasteride (but not finasteride) may increase insulin resistance in the liver. 

2017 Study Suggests 0.5 mg Dutasteride May Worsen Insulin Resistance 

A retrospective study of 230 men in 2017 by Traish et al suggested that dutasteride worsened insulin resistance. Men in the study were treated with dutasteride (0.5 mg/d) for lower urinary tract symptoms due to prostate enlargement and followed-up for 3 to 3.5 years. Dutasteride use resulted in increased blood glucose, glycosylated hemoglobin A, total cholesterol, and low-density lipoprotein cholesterol levels. In addition, dutasteride treatment increased activities of liver enzymes (AST, ALT), suggesting dysregulation of liver metabolism.

2019 Study Suggests that Either 5 mg Finasteride and 0.5 mg Dutasteride May Worsen Insulin Sensitivity. 

A large 2019 study by Wei et al again examined the links between finasteride, dutasteride and diabetes. The researchers compared large databases from both the UK to see if any links could be found and then analysed data bases from Taiwan. The UK database included 8,231 men using dutasteride, 30,774 men using finasteride and compared the frequency of new onset diabetes in these individuals compared to 16, 270 patients who were using another prostate drug known as tamsulosin (Flomax). The Taiwanese database included 1251 dutasteride users, 4194 finasteride users and 86 263 tamsulosin users.

After a mean follow up time of 5.2 years in the UK database, there was a modest increased risk of type 2 diabetes for users of dutasteride (adjusted hazard ratio 1.32, 95% confidence interval 1.08 to 1.61) and finasteride (1.26, 1.10 to 1.45) compared with tamsulosin. The study carefully controlled for body mass index, other drug use, smoking, alcohol consumption, hypertension and other health and behavioral characteristics. 

Results from the Taiwanese database were similar to the UK database. There was an increased risk of diabetes in dutasteride users ( 1.34, 95% confidence interval 1.17 to 1.54 ) as well as finasteride users ( 1.49, confidence interval 1.38 to 1.61 ) compared with tamsulosin). 

Conclusion 

Overall, this data in “real terms” equated to a 32 percent increased risk for developing diabetes in dutasteride 0.5 mg users and a 26 % increased risk in finasteride 5 mg users. What this means practically is that for every 1000 men treated with these drugs for 10 years, there will be 16 “new” cases of type 2 diabetes over those 10 years that can be attributed to the drug. The authors concluded that use of finasteride at 5 mg daily or dutasteride at 0.5 mg daily may increase the risk of type 2 diabetes. The authors propose that additional monitoring might be required for men starting these drugs, particularly in those with other risk factors for type 2 diabetes.

Reference

Duskova et al. Changes of metabolic profile in men treated for androgenetic alopecia with 1 mg finasteride. Endocr Regul. 2010 Jan;44(1):3-8.

Hazlehurst JM et al. Dual-5α-Reductase Inhibition Promotes Hepatic Lipid Accumulation in Man. Clin Endocrinol Metab 2016 Jan;101(1):103-13.

Traish A, Haider KS, Doros G, Haider A. Long-term dutaste- ride therapy in men with benign prostatic hyperplasia alters glucose and lipid profiles and increases severity of erectile dysfunction. Horm Mol Biol Clin Investig 2017;30.

Wei et al. Incidence of type 2 diabetes mellitus in men receiving steroid 5α-reductase inhibitors: population based cohort study/. BMJ 2019 Apr 10;365:l1204.