SUN-356 The Effects of Selective Serotonin Reuptake Inhibitors on Urinary Free Cortisol in Patients with Carney Complex and Primary Pigmented Nodular Adrenocortical Disease

PPNAD is a rare cause of ACTH-independent Cushing syndrome mainly associated with Carney complex (CNC). It is diagnosed by histologic examination or a 6-day Liddle test (LT) showing a paradoxical increase of >50% in 24-h urinary free cortisol (UFC) on the 2(nd) day of high-dose dexamethasone administration (Day 6 [D6]). PPNAD tissue has neuroendocrine features and can overexpress the serotonin (5-HT) synthesizing enzyme tryptophan hydroxylase type 2 and the 5-HT receptors types 4, 6, and 7, with formation of an illicit stimulatory serotonergic loop whose pharmacological inhibition in vitro decreases cortisol production [1]. SSRIs inhibit the reuptake of 5-HT and are used as 1(st)-line antidepressants. This is a retrospective cohort study of patients with CNC and PPNAD that underwent a LT with the objective to evaluate the effect of SSRIs on UFCs in these patients. Of the 34 patients (4-65 y) with CNC and PPNAD that had a LT at our institution between 2004 and 2018, 4 patients took an SSRI during testing. No statistically significant differences were demonstrated between the SSRI (S) group and the non-SSRI (NS) group in baseline UFCs and urine 17-hydroxycorticosteroids (17OHS) and the percent increase in UFC and 17OHS on D6. Specifically, the median (IQR) baseline UFC in the S group was 36 (13-252) mcg/24h (nl 4-56) vs 35 (13-98) mcg/24h in the NS group (P=0.95). Baseline 17OHS were 11 (8-18) mg/mg creatinine (Cr) (nl ≤6) in the S group vs 8 (5-11) mg/mgCr in the NS group (P=0.27). The percent change in UFC was 208 (93-683)% in the S group and 185 (28-364)% in the NS group (P=0.89), while the percent change in 17OHS was 56 (40-87)% in the S group and 67 (16-92)% in the NS group (P=0.91). On D6, the S group appeared to have higher UFC [118 (63-635) mcg/24h vs 112 (58-201) mcg/24h; P=0.64] and 17OHS [16 (10-39) mg/mgCr vs 13 (7-17) mg/mgCr; P=0.25] than the NS group, but these were not statistically significant. Though these data do not confirm an effect of SSRIs on UFC and ultimately cortisol production in PPNAD, and the percent change in UFC during the LT was similar between both groups, the higher D6 UFC in the S group, when the baseline UFCs between the 2 groups were similar may suggest a degree of increased cortisol production in the S group. The data are limited by the small number of patients in the S group (n=4). In addition, 50% of patients in the S group vs 77% in the NS group underwent adrenalectomy, which is indicative of more severe disease in the NS group. More data are needed from this cohort to determine if SSRI use affects cortisol production in vivo, as this may have significant diagnostic and therapeutic implications for patients with CNC and PPNAD. Reference: 1. Bram, Z., et al., PKA regulatory subunit 1A inactivating mutation induces serotonin signaling in primary pigmented nodular adrenal disease. JCI Insight, 2016. 1(15): p. e87958.