Finasteride does not completely suppress DHT production because it lacks significant inhibitory effects on the 5α-reductase type I isoenzyme, with more than 100-fold less inhibitory potency for type I as compared to type II (IC50 = 313 nM and 11 nM, respectively). This is in contrast to inhibitors of all three isoenzymes of 5α-reductase like dutasteride, which can reduce DHT levels in the entire body by more than 99%. In addition to inhibiting 5α-reductase, finasteride has also been found to competitively inhibit 5β-reductase (AKR1D1). However, its affinity for the enzyme is substantially less than for 5α-reductase (an order of magnitude less than for 5α-reductase type I) and hence is unlikely to be of clinical significance.As of 2012, the tissues in which the different isozymes of 5α-reductase are expressed are not fully clear. This is because different investigators have obtained varying results with different reagents, methods, and tissues examined. However, the different isozymes of 5α-reductase appear to be widely expressed, with notable tissues including the prostate gland, seminal vesicles, testes, epididymides, skin, hair follicles, liver, kidneys, and brain, among others.By inhibiting 5α-reductase and thus preventing DHT production, finasteride reduces androgen signaling in tissues like the prostate gland and the scalp. In the prostate, this reduces prostate volume, which improves BPH and reduces risk of prostate cancer. Finasteride reduces prostate volume by 20 to 30% in men with benign prostatic hyperplasia.
As a result, pingueculae tend to occur more often on the nasal side of the eye. While most pingueculae are found in people over the age of 40, they are not uncommon in 20- and 30-year-old adults who spend significant time in the sun. The surface of the conjunctival tissue overlying a pinguecula interferes with the normal spreading of the tear film. The tear ferning test reveals abnormalities of the mucous component of the tear film, making it useful as a predictor of a persons tolerance of hydrophilic soft contact lenses. Contact lens intolerance can also result from the elevation of the peripheral edge of the contact lens if it overlies a pinguecula. The plural form of pinguecula is pingueculae. Pinguecula is derived from the Latin word "pinguis" for fat or grease. Associated conditions
A pinguecula is one of the differential diagnoses for a limbal nodule. It may have an increased prevalence in Gauchers disease. Diagnosis
Diagnosis of pinguecula is usually done by an eye care professional during routine eye examination using slit lamp. Conjunctival biopsy may be advised if malignancy is suspected. Treatment
Pingueculae may enlarge slowly over time, but are a benign condition, usually requiring no treatment. Artificial tears may help to relieve discomfort, if it occurs. If cosmesis is a concern, or if there is discomfort in contact lens use, surgical excision may be done. Occasionally, a pinguecula may become inflamed, a condition called pingueculitis. The cause of pingueculitis is unknown and there are no known infectious agents associated with it.