Endocrine Abstracts

Introduction: Ketoconazole is an antifungal agent that, in a high dose, suppresses adrenocortical steroidogenesis by inhibition of cytochrome P-450 dependent enzymes. Currently, ketoconazole is used to decrease cortisol production in patients with Cushing’s syndrome. However, ketoconazole often causes gastrointestinal side effects and hepatotoxicity. Fluconazole may also inhibit steroidogenesis and has the advantage over ketoconazole that it has less side effects. Therefore, we compared the effects of ketoconazole and fluconazole on primary cultures of adrenocortical tissue, as well as on the human adrenocortical carcinoma cell line HAC15.

Methods: Primary cultures of human adrenocortical tissue and HAC15 cells were incubated with ketoconazole (0.05–100 μM) and fluconazole (10–1000 μM). Supernatant cortisol concentrations were measured after 96 h (primary cultures) or 72 h (HAC15) of incubation.

In addition, the effects on cell growth and DNA fragmentation (measure of apoptosis) were measured.

Results: Both ketoconazole and fluconazole decreased cortisol production in a dose-dependent fashion by ~70–90% (highest concentration), but not cell number in primary cultures of adrenocortical cells. Ketoconazole was significantly more potent than fluconazole with a 7- to 30-fold potency difference, depending on the culture.

In HAC15 cells, ketoconazole reduced cortisol production by 80%, while fluconazole reduced cortisol production by only 55%, corrected for cell number (IC₅₀ 0.42 and 11 μM, respectively). Additionally, we found that ketoconazole (IC₅₀ 9 μM) and fluconazole (IC₅₀ 74 μM) dose- and time dependently inhibited HAC15 cell growth, at least in part by inducing apoptosis.

Discussion: Both ketoconazole and fluconazole inhibit cortisol production in primary adrenocortical cells and HAC15 cells and decrease HAC15 cell growth in a dose-dependent fashion. Since our IC₅₀ values are within the range of earlier reported steady state serum concentrations, fluconazole, as an alternative to ketoconazole, may be applied to decrease cortisol production in Cushing’s disease or cortisol producing adrenocortical adenomas and carcinomas.