Failure of somatostatin analogue to control Cushing's syndrome in two cases of ACTH-producing carcinoid tumours.

OBJECTIVE

To determine the effectiveness of somatostatin analogue (octreotide) in controlling hypercortisolism in two patients with ectopic ACTH-producing carcinoid tumours, and to review the literature.

DESIGN

The two patients were treated with octreotide administered by subcutaneous injection, for 5 days with 150 micrograms three times daily and for 7 days with 100 micrograms three times daily respectively. They were subsequently treated with oral metyrapone 250 mg three times daily.

PATIENTS

Patient 1 had a metastatic carcinoid tumour but the primary was not identified. Patient 2 had a pulmonary carcinoid. Cushing's syndrome due to ectopic ACTH syndrome was established by demonstration of failure of cortisol suppression by dexamethasone, elevated ACTH levels, and immunoperoxidase staining for ACTH within the tumours.

MEASUREMENTS

Urinary free cortisol (UFC) was measured on consecutive days during treatment with octreotide. Serum cortisol and ACTH levels were taken daily in patient 2, and on days 0 and 3 in patient 1.

RESULTS

Patient 1 had a baseline 24-hour urinary free cortisol of 5340 nmol/24 h, serum cortisol of 915 nmol/l, and serum ACTH of 163 ng/l (ACTH ng/l x 0.23 = pmol/l). After 3 days of octreotide, serum cortisol was 782 nmol/l and ACTH 164 ng/l. Twenty-four hour urinary free cortisol was 4136 nmol/24 h after 7 days of treatment. Metyrapone, however, resulted in a rapid fall in urinary free cortisol to 290 nmol/24 h, with marked clinical improvement. Patient 2 had a baseline 24-hour urinary free cortisol of 2520 nmol/24 h, serum cortisol of 747 nmol/l, and ACTH of 103 ng/l. Urinary free cortisol rose to 2970 nmol/24 h on day 6 of treatment with octreotide. Serum cortisol and ACTH levels fell slightly to 611 nmol/l and 70 ng/l respectively. On changing to metyrapone, the urinary free cortisol fell to 821 nmol/24 h in 4 days.

CONCLUSIONS

Octreotide failed to significantly reduce 24-hour urinary free cortisol, serum cortisol and ACTH in the two patients reported. We conclude that it should probably not be regarded as primary treatment for control of hypercotisolism in patients with ACTH-producing carcinoids, but reserved as adjunctive therapy.