Introduction: Low or borderline cortisol concentrations and impaired response to dynamic testing have been reported in patients with fibromyalgia, potentially related to hypothalamus-pituitary dysfunction.1,2 Superimposed adrenal insufficiency (AI) may contribute to some fibromyalgia symptoms or delay improvement in patients enrolled in fibromyalgia treatment programs. We hypothesized that a subset of patients with fibromyalgia have: 1) partial secondary AI and concomitant growth hormone (GH) deficiency 2) a discordance in Cosyntropin stimulation test and 3) improvement in fibromyalgia symptoms with initiation of glucocorticoid and/or GH replacement.
Design: This was a retrospective study of patients with fibromyalgia diagnosed with partial secondary AI based on abnormal insulin tolerance test (peak cortisol < 18 mcg/dL) at our institution from June 2002 to August 2019. Patients were excluded if they had other reasons for adrenal insufficiency, including steroid exposure and opioid use.
Results: We identified 22 patients (18 women, 82%) diagnosed with partial AI at a median age of 38 years (range 19-65). The fibromyalgia symptoms included fatigue (n=22, 100%), pain (n=22, 100%), sleep disturbance (n=15, 68%), and bowel changes (n=13, 59%). The median morning cortisol concentration was 8.6 mcg/dL (range 1.1-11); 9 patients (41%) had a morning cortisol concentration below the normal range (7 mcg/dL). The median ACTH level was 15.5 pg/mL (range 7.7-54). Nineteen patients had baseline IGF1 levels, with a median z-score of -0.94 (range -1.96 to 1.70). MRI pituitary imaging was performed in 20 patients and showed no significant pituitary pathology.
All patients achieved hypoglycemia <=40 mg/dL during the insulin tolerance test. Peak median cortisol level was 11 mcg/dL (range 5.4-17). Nineteen patients (86%) also had partial GH deficiency (defined as a peak GH < 4 ng/mL) with a median GH level of 0.36 ng/mL (range 0.03-3.83). Cosyntropin stimulation test was performed in 13 patients (59%) with a 1 mcg dose in 2 patients and 250 mcg dose in 11 patients. The peak cortisol was >=18 mcg/dL in 10 (77%) patients. All patients were started on physiologic glucocorticoid replacement, and 12 patients were started on GH replacement. Endocrinology follow-up information was available for 13 patients, and 8 (62%) reported symptom improvement after starting treatment.
Conclusions: Patients with fibromyalgia can have co-existing partial secondary AI and GH deficiency as defined by insulin-induced hypoglycemia. Cosyntropin stimulation test can be used in patients with fibromyalgia, but a normal test does not rule out partial secondary AI. Replacing the underlying deficiency improved symptoms in some patients demonstrating certain fibromyalgia symptoms may overlap with AI and GH deficiency.