ACTH Levels After Surgery Help Predict Remission, Recurrence in Cushing’s, Study Suggests

Levels of adrenocorticotropic hormone (ACTH) in circulation after pituitary surgery may help predict which Cushing’s disease patients will achieve early remission and which will eventually see the disease return, a study shows.

Also, the earlier that patients reached their lowest peak of ACTH levels, the better their long-term outcomes.

The study, “Prognostic usefulness of ACTH in the postoperative period of Cushing’s disease,” was published in the journal Endocrine Connections.

Removing the pituitary tumor through a minimally invasive surgery called transsphenoidal surgery is still the treatment of choice for Cushing’s disease patients. But not all patients enter remission, and even among those who do, a small proportion will experience disease recurrence.

While cortisol levels have been suggested as a main predictor of remission and recurrence, there is no consensus as to which cutoff point should be used after surgery, or the best time for measuring this hormone.

Because Cushing’s disease is caused by an ACTH-producing tumor in the pituitary gland, and ACTH has a short half-life (approximately 10 minutes), it is expected that ACTH levels drop markedly within a few hours after surgery.

Thus, a group of researchers in Spain aimed to determine whether blood levels of ACTH could be useful for predicting remission of Cushing’s disease both immediately after surgery (defined as less than 72 hours) and in the long term.

Researchers analyzed 65 patients with Cushing’s disease who had undergone transsphenoidal surgery (seven required a second intervention) between 2005 and 2016. Remission within three months was seen in 56 of 65 cases; late disease recurrence was seen in 18 of 58 cases.

Investigators measured the ACTH nadir concentration (defined as the lowest concentration) and the time taken to reach nadir levels after surgery, as well as the plasma ACTH concentration before hospital discharge.

While ACTH levels had no predictive value, the team found that people who went into remission had significantly lower ACTH nadir levels and ACTH levels at discharge. On the other hand, levels of ACHT nadir and at discharge were significantly higher for people who experienced a relapse, compared to those who remained in remission.

Using artificial intelligence algorithms, the researchers further found that ACTH nadir, ACTH at discharge, and cortisol nadir values were all of great relevance to predict remission within three months.

Analysis indicated that using a cutoff point of 3.3 pmol/L of ACTH after surgery and before discharge gave the best sensitivity and specificity for predicting a patient’s prognosis.

Researchers further found that the time patients took to reach their ACTH nadir, regardless of nadir levels, also influenced their outcomes. In fact, patients reaching this nadir in less than than 46 hours more likely achieved early remission.

And taking longer than 39 hours to reach the ACTH nadir was significantly more frequent in patients who experienced recurrence. This indicates that the time to ACTH nadir is an important measure for prognosis.

“In the immediate postoperative period of patients with [Cushing’s disease], the ACTH concentration is of prognostic utility in relation to late disease remission,” the researchers said.

Overall, “we propose an ACTH value <3.3 pmol/L as a good long-term prognostic marker in the postoperative period of CD. Reaching the ACTH nadir in less time is associated to a lesser recurrence rate,” the study concluded.