Characteristics and response cutoff of octreotide suppression test in thyrotrophin (TSH)-secreting pituitary adenomas

ContextSomatostatin analogs are recommended for preoperative therapy in thyrotrophin secreting pituitary adenomas (TSHomas). Octreotide suppression test (OST) was designed to differentiate TSHomas with resistance to thyroid hormones, while its ability to test the sensitivity of SSA has not been fully studied. ObjectiveTo test the sensitivity of SSA in TSHomas with OST. PatientsWe collected 48 pathologically confirmed TSHoma patients with complete 72 h' data of OST into analysis. InterventionOctreotide suppression test. Main OutcomeSensitivity timepoint and cutoff of OST. ResultsDuring the entire OST, the TSH descended maximally 89.07% (73.85%, 96.77%), while the FT3 and FT4 declined slowly [43.40% (37.80%, 54.44%) and 26.59% (19.01%, 33.13%), respectively]. The 24th hour was the timepoint wherein the stability occurs for TSH, and the 48th hour for FT3 and FT4 during OST. In the patients who received both short- and long-acting somatostatin analogs (SSA), the 24-h timepoint was the most predictive timepoint for the percentage of TSH decline (Spearman's rank correlation analysis, r = .571, p < .001), while the 72-h timepoint was optimal for predicting the magnitude of TSH decline (Spearman's rank correlation analysis, r = .438, p = .005). In the 24th timepoint, a positive correlation was also observed between TSH suppression rate and the percentage decrease and absolute value decrease of FT3 and FT4. Furthermore, in patients treated with long-acting SSA, the 72-h timepoint was optimal for predicting both the percentage (Spearman's rank correlation analysis, r = .587, p = .01) and magnitude (Spearman's rank correlation analysis, r = .474, p = .047) of TSH decline. The 24th hour was the optimal timepoint with 44.54% (50% of median value of TSH in 72-hOST) decrease of TSH being the observing cutoff. The adverse effect of OST was predominantly occurred in the gastrointestinal system and no severe event occurred during OST. Paradoxical response could occur in OST and it did not influence the effect of SSA as long as sensitivity was confirmed. A high level of hormonal control was achieved in the SSA-sensitive patients. ConclusionOST can be used as an efficient tool to guide the adequate use of SSA.

Automated summary

This study found that the octreotide suppression test can be used as an efficient tool to predict the decline of thyroid-stimulating hormone in patients with thyrotrophin-secreting pituitary adenomas. The 24-hour and 72-hour timepoints were particularly effective in guiding the use of somatostatin analogs.