Endocrine Abstracts

Case history: A 45-year-old male was referred to Endocrinology from the Infectious Diseases clinic for investigation of possible adrenal insufficiency. The patient had multiple co-morbidities including asthma, hepatitis B and HIV. The patient’s GP had introduced a fluticasone inhaler to control the symptoms of his asthma, however when the patient was seen in Infectious Diseases clinic as an interaction with his protease inhibitor (atazanavir) was suspected. A random cortisol test was performed, showing a cortisol of less than 20, thus the patient’s fluticasone inhaler was stopped and he was referred to Endocrinology. His history and examination showed no symptoms nor signs of adrenal insufficiency.

Investigations: A short synacthen test and subsequent long synacthen test were requested when the patient had discontinued use of the fluticasone inhaler for 1 week. Thyroid function tests were normal. HIV and hepatitis B viral loads were both undetectable.

Results and treatment: SST result: 0 min cortisol 158, 30 min cortisol 289, 60 min cortisol 315. LST result: 0 min cortisol 348, 60 min cortisol 501, 240 min cortisol 584, 360 min cortisol 600, 480 min cortisol 645, 1,440 min cortisol 543 and 2,880 min cortisol 393, ACTH level 49.2. The patient was reassured that although his SST was suboptimal, his subsequent LST result was completely satisfactory. It was explained he had temporary adrenal insufficiency with the combination therapy, which had resolved over time after withdrawal of the fluticasone inhaler.

Conclusion and points for discussion: Interactions between protease inhibitors and inhaled or intranasal corticosteroids are well documented in the literature. The drug-drug interaction is secondary to the inhibition of hepatic cytochrome P450 3A4 isozyme by protease inhibitors, which is partly responsible for the metabolism of steroids. This case concerns concurrent use of a protease inhibitor and inhaled corticosteroid, leading to low cortisol levels with temporary adrenal suppression. Such interactions have become a common source of referral to endocrinology. Could this interaction be minimised by the use of an alternative steroid inhaler such as beclometasone, or the use of an alternative anti-retroviral medication?