Thank you for your question. You didn’t submit an image, but you describe you started finasteride about 8 months prior, experienced a certain amount of hair shedding, followed by significant growth and thickening of your hair. You state you also had another episode of shedding where only one side of the head had growth. You’re asking if finasteride can cause telogen effluvium. I can share with you how I guide my patients when it comes to the drug finasteride, and treatment of hair loss. A little background: I’m a Board-certified cosmetic surgeon and Fellowship-trained oculofacial plastic and reconstructive surgeon. I have been in practice in Manhattan and Long Island for over 20 years. I am also the founder of TrichoStem™ Hair Regeneration Centers, a system we developed over several years starting about 7 years ago for men and women with thinning hair bot . It has worked out very favorably as an alternative for people who didn’t want to take finasteride because of the concerns of side-effects. Nonetheless, we still prescribe this drug as part of hair loss management when appropriate. Telogen effluvium is an early entry into the resting stage of the hair growth cycle. Hair growth is 3 stages: anagen, catagen, telogen. Anagen is the active growing stage. Telogen effluvium is usually the result of a preceding highly stressful event 2-5 months prior, which then results in significant hair shedding. This is something we do see fairly often in patients who have undergone general anesthesia, who had significant life stressors like death of a family member. We have patients who are young such as students who have very high stress levels with exams, so they have shedding. Finasteride is a blocker of an enzyme called 5-alpha reductase that converts testosterone to dihydrotestosterone(DHT). It has been my observation when it comes to hair loss that variables we can use to determine the benefits of finasteride are the age of onset, the rate of progression, and severity of hair loss. When I see a younger person who has been losing hair, say in their 20s, and has significant hair loss, we ask why 80% of their contemporaries don’t have hair loss? One possible variable is relative DHT sensitivity. Someone who shows up to the office in their early 60s or 70s and have never taken finasteride, but starting to notice some hair loss has low DHT sensitivity. With the role of finasteride as a DHT blocker, I always try to differentiate where that fits in the treatment of hair loss, versus the role of a treatment like Hair Regeneration. Hair Regeneration is our treatment we developed which is a combination of platelet-rich plasma with extracellular matrix. This was derived out of the intention of helping our hair transplant patients with better graft yields and healing of the donor area. A serendipitous benefit was a lot of thinning hair became thicker. Over the course of several years, I developed an algorithm of formulations and methods of delivery based on age, gender, and degree of hair loss, so over the course of time we developed what became Hair Regeneration, and now TrichoStem™ Hair Regeneration. The point is this treatment will stop progression, reactivate hair that’s not growing such as those in the telogen stage, and thicken existing thinning hair. The differentiation is DHT is effectively a toxin to your hair. The absence of a toxin may allow for growth as it has in your situation, but it doesn’t stimulate hair growth. For the right patient, a combination approach of finasteride with Hair Regeneration has been valuable. The overall majority of our patients do not take finasteride because of fears of sexual side-effects. Clinically speaking, in my own practice and those of my colleagues and people I discuss this with meetings all over the world, less than 2% of people have sexual side-effects. This is reflective with one of the original studies which showed both the active drug group and the placebo group where both had less than 2% sexual side-effects. This is a very controversial subject, and I don’t want to take away the beliefs and concerns of people who believe they have an issue with the drug ,but clinically, in my own practice, this has been my experience. That said, as far as the direct connection between finasteride and telogen effluvium, in my clinical experience, there is none. You may want to think about the other limitations of finasteride as it doesn’t stop progression, but slows it down. We have had patients in our practice who have been in finasteride for 15 years who still slowly progress, but they had more hair than they would’ve had if they weren’t on finasteride. In those patients we’ve done the injection treatment Hair Regeneration for, they’ve had significant growth and improvement. This means we’re working from a different mechanism other than DHT ,and here’s a potential for synergy in the right patient. For now, it is important you discuss this with the doctor who prescribed the finasteride. Look at your own situation as far as possible stressors. Remember, telogen effluvium can occur from stress that happened 2-5 months earlier, but I would still advise since finasteride has been successful for you, as long as you don’t have any other issues, to continue taking it, and learn more about treatments like Hair Regeneration which can help further the scalp coverage you are enjoying now. I hope that was helpful, I wish you the best of luck, and thank you for your question.