Numerous small studies have investigated the effects of oral ketoconazole on hormone levels in humans. It  has been found in men to significantly decrease testosterone and estradiol levels and to significantly increase luteinizing hormone, progesterone, and 17α-hydroxyprogesterone levels, whereas levels of androstenedione, follicle-stimulating hormone, and prolactin were unaffected. The ratio of testosterone to estradiol is also decreased during oral ketoconazole therapy in men. Suppression of testosterone levels by ketoconazole is generally partial and has often been found to be transient. Better effects on suppression of testosterone levels have been observed in men when ketoconazole is combined with a GnRH agonist to suppress the hypothalamic–pituitary–gonadal axis, which prevents compensatory upregulation of luteinizing hormone secretion and consequent activation of gonadal testosterone production. In premenopausal women with polycystic ovary syndrome, ketoconazole has been found to significantly decrease levels of androstenedione and testosterone and significantly increase levels of 17α-hydroxyprogesterone and estradiol. Studies in postmenopausal women with breast cancer have found that ketoconazole significantly decreases androstenedione levels, slightly decreases estradiol levels, and does not affect estrone levels. This indicates minimal inhibition of aromatase by ketoconazole in vivo in humans. Ketoconazole has also been found to decrease levels of endogenous corticosteroids, such as cortisol, corticosterone, and aldosterone, as well as vitamin D.Ketoconazole has been found to displace dihydrotestosterone and estradiol from sex hormone-binding globulin in vitro, but this was not found to be relevant in vivo. Other activities
Ketoconazole has been found to inhibit the activity of the cation channel TRPM5.
Ketoconazole, sold under the brand name Nizoral among others, is an antiandrogen and antifungal medication used to treat a number of fungal infections. Applied to the skin it is used for fungal skin infections such as tinea, cutaneous candidiasis, pityriasis versicolor, dandruff, and seborrheic dermatitis. Taken by mouth it is a less preferred option and only recommended for severe infections when other agents cannot be used. Other uses include treatment of excessive male-patterned hair growth in women and Cushings syndrome.Common side effects when applied to the skin include redness. Common side effects when taken by mouth include nausea, headache, and liver problems. Liver problems may result in death or the need for a liver transplantation. Other severe side effects when taken by mouth include QT prolongation, adrenocortical insufficiency, and anaphylaxis. It is an imidazole and works by hindering the production of ergosterol required for the fungal cell membrane, thereby slowing growth.Ketoconazole was patented in 1977 by Belgian pharmaceutical company Janssen, and came into medical use in 1981. It is available as a generic medication and formulations that are applied to the skin are over the counter in the United Kingdom. In 2019, it was the 171st most commonly prescribed medication in the United States, with more than 3 million prescriptions. The formulation that is taken by mouth was withdrawn in the European Union and in Australia in 2013, and in China in 2015. In addition, its use was restricted in the United States and Canada in 2013.