Effect of Supplemental Hydrocortisone During Stress in Prednisolone-induced Adrenal Insufficiency

In this double-blinded randomised placebo-controlled clinical trial, the aim is to determine the effect of supplemental hydrocortisone compared with placebo during mild to moderate physical or mental stress on health related quality of life in patients with polymyalgia rheumatica (PMR)/giant cell arteritis (GCA) on ongoing low-dose prednisolone diagnosed with glucocorticoid-induced adrenal insufficiency. The main emphasis is on fatigue (primary outcome) and daily variation hereof during periods of stress.

The study will include patients with PMR/GCA on ongoing prednisolone treatment in a low dose of \> 0 mg/day and ≤5mg/day. Eligible patients will undergo a Synacthen® test and 250 patients with a stimulated cortisol level \<420 nmol/l (biochemical adrenal insufficiency) will be randomised to either placebo or hydrocortisone supplemental doses during stress. Patients will continue prednisolone treatment and tapering hereof according to current clinical guidelines for PMR/GCA and add supplemental hydrocortisone/placebo in situations of stress according to study protocol. In situations of severe stress (potential adrenal crisis) patients will receive open label hydrocortisone treatment according to routine clinical care. The duration of RESCUE is 6 months but stops earlier if the patient stops prednisolone treatment earlier. In case of a flare of PMR/GCA during the study where prednisolone is increased to \>5mg/day for e.g. 5 weeks the study is prolonged accordingly 5 weeks.

Seventy-five patients with stimulated cortisol ≥420 nmol/l (normal adrenal function) will be used as a reference group. The participants will undergo screening and baseline examinations, 3 month's reporting of HRQoL, and with patient consent follow-up through medical records on prednisolone treatment characteristics, and number of hospitalisations.

Eligibility Criteria:
Inclusion Criteria:

* Age ≥ 50 years
* Women must be postmenopausal (FSH is measured at the screening visit)
* A diagnosis of PMR/GCA, or both conditions combined.
* Treatment with prednisolone ≥12 weeks
* Ongoing prednisolone treatment, with current daily prednisolone dose \> 0 mg and ≤5 mg. The dose must have been ≤5 mg for minimum 2 weeks at the time of the screening visit.

Exclusion Criteria:

* Known primary or secondary adrenal insufficiency
* Known Cushing's Syndrome
* Known allergy towards study medication ingredients
* Severe comorbidity: Heart failure (New York Heart Association class IV); Kidney failure with an estimated glomerular filtration rate \<30 mL/min (Chronic kidney disease stage 4-5); Liver disease in the form of cirrhosis; Active cancer; Known severe immune deficiency; A history of psychiatric disease requiring treatment by a psychiatric department (for affective disorders only if within the last year before study entry)
* Alcohol consumption \>21 units per week
* Planned major surgery during the study period at study entry.
* Use of drugs that interfere with cortisol metabolism/measurements: Systemic oestrogen treatment (discontinued \< 1 month before inclusion), Treatment with strong CYP3A4 inhibitors or inducers, Use of other glucocorticoid formulations (Inhaled corticosteroids, intraarticular or intramuscular injections, steroid creams European steroid group IV-V used in the genital area. Note: Permitted glucocorticoid formulations: Eye-drops, nasal spray, glucocorticoid creams European steroid group I-III, and European steroid group IV-V used in the non-genital area only.)
* Inability to provide written informed consent.