Eli Lilly (NYSE: LLY) has something to be thankful for this week. Yesterday, the Food and Drug Administration approved Axiron, its testosterone replacement therapy.

Testosterone therapy isn't revolutionary; there are plenty already on the market. But I think Eli Lilly might have a marketing advantage since Axiron is applied with an applicator in the armpit, kind of like putting on deodorant.

I imagine a lack of testosterone is a little emasculating, but putting on deodorant, covering up manly smells, is pretty masculine -- certainly manlier than putting on a patch or popping a pill.

That isn't to say that marketing Axiron is going to be easy for Eli Lilly. The company estimates that as many as 13 million men over the age of 45 have symptoms of testosterone deficiency, but I'm guess most of them are going undiagnosed. Eli Lilly's biggest challenge will likely be getting the men in to see their doctor.

Fortunately, Eli Lilly has experience with under-diagnosed conditions. Eli Lilly sells Cymbalta for fibromyalgia, a painful disease that is often not diagnosed. Awareness campaigns can increase the number of patients that ask their doctor about the disease and hopefully get prescribed the drug. Of course it also helps the competitors. I'm sure Forest Labs (NYSE: FRX) and Cypress Bioscience (Nasdaq: CYPB) are thankful for all of Eli Lilly's work bringing awareness about the disease before their own fibromyalgia drug, Savella, was approved.

Eli Lilly also has experience with touchy subjects since it markets the erectile dysfunction drug Cialis. The drug was third to the market behind Pfizer's (NYSE: PFE) Viagra and GlaxoSmithKline (NYSE: GSK) and Bayer's Levitra, but Cialis has held its own with marketing campaigns with couples lounging in bathtubs in the middle of nowhere.

Eli Lilly needs Axiron to be at least a mild success to justify licensing the drug from Australia's Acrux. Eli Lilly owes Acrux $87 million now that the drug has been approved, in addition to the $53 million it's already paid. If Eli Lilly plays its commercials right, that shouldn't be a problem.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.