Reduction of cortisol levels after single intra-articular and intramuscular steroid injection.

Background: This study was undertaken to determine the influence of single intra-articular or intra muscular injections of methylprednisolone acetate on the hypothalamic-pituitary-adrenal axis.
Patients and Methods: Twenty-one patients with rheumatic disease who had never been treated with systemic glucocorticoids and had not received local injections of these agents for the preceding 2 months, were given 40 mg of methylprednisolone acetate. Group I (11 patients) received one intra-articular injection into the knee, and Group II (10 patients) received the same dose intramuscularly.
Results: In Group I, serum cortisol levels were significantly decreased 24 hours after injection (228.2 +/- 8.7 nmol/L versus 193 +/- 16.3 nmol/L; P < 0.05). Serum cortisol levels were decreased in 9 of the 11 patients, by an average of 21.5%. Two patients' levels were below 138 nmol/L, which is considered to be the lower limit of normal range. Serum cortisol levels were below normal range in 3 patients 72 hours after intra-articular steroid injection. In Group II, serum cortisol levels were significantly decreased at 72 hours after injection (239.6 +/- 10.3 nmol/L versus 175.6 +/- 21.4 nmol/L; P < 0.01). Three patients' levels were below normal. By 72 hours postinjection, serum cortisol concentrations in 9 of 10 patients were decreased by an average of 31% compared to preinjection values.
Conclusion: The present study suggests that decreased adrenocortical secretion, as reflected in depressed cortisol levels, can result from a single, low-dose, intra-articular or intramuscular injection of depot corticosteroids.