Blunted ACTH and cortisol responses to systemic injection of corticotropin-releasing hormone (CRH) in fibromyalgia: role of somatostatin and CRH-binding protein.

Thirteen female patients suffering from fibromyalgia (FM) and thirteen female age-matched controls were intravenously injected with a bolus dose of 100 microg corticotropin-releasing hormone (CRH), and the evoked secretion pattern of ACTH, cortisol, somatostatin, and growth hormone (GH) was followed up for two hours, together with the plasma levels of CRH. The increases of ACTH and cortisol following CRH were not significantly different between controls and FM patients. The increase of plasma CRH following its injection was significantly higher in FM patients and lasted about 45 min, paralleled by an increase of somatostatin with a similar time course. Basal GH levels were significantly lower in FM patients. GH increased in FM patients 90 min after injection of CRH, coincident with decreasing CRH and somatostatin levels, while GH levels in controls rather decreased with the lowest values occurring 90 min after CRH. The results support the concept that the hormonal secretion pattern frequently observed in FM patients is primarily caused by CRH, possibly as a response to chronic pain and stress. The elevated levels of CRH in the circulation of FM patients suggest elevated levels of CRH-binding protein, which could explain why the levels of ACTH and cortisol between controls and FM following CRH do not differ.