Hypothalamo-pituitary-adrenal axis after a single epidural triamcinolone injection

To quantify adrenocorticotropin and cortisol secretion after epidural glucocorticoid injection.

Eight men (ages 25–63 year) were studied at baseline, 1, 4, and 12 weeks after triamcinolone (80 mg) injection epidurally. Adrenocorticotropin (pg/mL) and cortisol (µg/dL) were measured every 10 min for 4 h, and after Corticotropin-releasing hormone (CRH) (1 µg/kg) injection.

Epidural triamcinolone markedly suppressed: (1) pre-CRH injection ACTH (from 18 ± 3.1 to 4.8 ± 0.4: P < 0.01) and cortisol (from 12.2 ± 1.6 to 1.6 ± 0.3: P < 0.0001) at week 1, with recovery at 4 weeks, and (2) CRH-stimulated 3-h summed ACTH (from 633 ± 116 to 129 ± 10 pg/mL, P < 0.0001), and 3-h summed cortisol at week 1 (from 385 ± 29 to 56 ± 22 µg/dL, P < 0.0001) and 4 weeks (284 ± 53; P < 0.01). Serum cortisol was <18 µg/dL in eight of eight men at 4 weeks, and six of eight men at week 12. Urinary-free cortisol (µg/24 h) remained low at week 12: baseline (60 ± 6.5); week 1 (9.0 ± 1.3, P < 0.01); week 4 (36 ± 8.6) and week 12 (38 ± 4.1). Urinary cortisol/cortisone ratios rose at week 4 only. Serum triamcinolone peaked at week 1 (16/16 samples), declining at week 4 (13/16 samples) and week 12 (6/16 samples).

Relatively small group.

Epidural triamcinolone suppresses unstimulated and CRH-stimulated ACTH and cortisol secretion for 1–4 weeks but urinary free cortisol ≥12 weeks. Suppression of ACTH and cortisol after glucocorticoid treatment is thus complex.