Abnormal Levels of Cortisol and Cortisone in Patients with Prurigo Nodularis.

Sir,

Prurigo nodularis (PN) is a highly pruritic condition caused by a vicious circle of repeated itching and scratching.[1] PN as a chronic stressor would result in an individual's psychological and physiological responses. Previous studies had investigated the psychological responses related to PN,[234] such as emotional and psychosomatic responses. For instance, most of the studies had demonstrated that patients with PN showed severer symptoms of anxiety and depression than healthy control group and also had a higher prevalence of anxiety, depression, and other psychological symptoms than the patients with psoriasis vulgaris.[3] However, the PN-related physiological responses still remain poorly understood. Moreover, limited data are available on investigating the hypothalamic-pituitary-gonadal (HPG) axis activity in skin diseases. Simultaneous use of dehydroepiandrosterone (DHEA), testosterone, and progesterone as important sex steroids were recommended to assess the activity of the HPG axis. To date, no study investigated the activities of the hypothalamic-pituitary-adrenal (HPA) and HPG axes in patients with PN and a few studies examined the association between pruritus severity and steroid levels in patients with PN. Taken together, this study aimed to investigate the activities of the two neuroendocrine systems including the HPA and HPG axes and the interactions within one neuroendocrine system among patients with PN by examining the differences between the patients with PN and healthy control group in the levels of the biomarkers that were five steroids and three ratios. Then, it screened the sensitive biomarkers to assess the pruritus severity in patients with PN by examining the association of these biomarkers with the pruritus severity. The screening criteria are whether the biomarkers show the intergroup differences and show moderate or over correlation with the pruritus severity.

This prospective case–control study was performed on 36 newly registered consenting patients with PN and 36 age-matched and sex-matched (P = 0.306 and 0.421, respectively) healthy control group. Demographic and disease data were recorded. The pruritus severity was determined by the prurigo score at the initial visit. All included patients were outside a washout period of 2 months from systemic medication and 2 weeks from topical medication. Patients with known autoimmune disease, malignancy, or serious chronic systemic disease and pregnant and lactating women were excluded. The study was approved by the Health Science Research Ethics Board of Southeast University, the Ethical Committee of Peking University Shenzhen Hospital (no. 20160427). Written informed consent about all data for scientific research was obtained from all participants.

Blood samples (1 mL) were collected from the antecubital vein after a light application of a tourniquet and 200 μL supernatant plasma was separated and stored at −80°C. Liquid chromatography (Agilent 1200 HPLC system; Agilent, Waldbronn, Germany) and tandem mass spectrometry (ABI 3200 Qtrap; ABI, Foster City, CA, USA) (liquid chromatography–mass spectrometry/mass spectrometry) was used to detect the concentrations of cortisol, cortisone, DHEA, testosterone, and progesterone in plasma.[56] The method showed good linearity (R2> 0.99) in the range of 0.03–500 ng/mL, and the limit-of-quantitation were 0.1, 0.4, 0.6, 0.1, and 0.1 ng/mL for cortisol, cortisone, DHEA, testosterone, and progesterone, respectively. The coefficients of variation for intra-day and inter-day (n = 5) assays were less than 15%. All statistical tests were performed using the IBM SPSS (version 22.0) software at a significance level of a = 0.05 after testing the normality of the variables. An analysis of correlations of the subpopulations with various disease parameters in the patients was conducted. Group comparisons were made with the Chi-square test or analysis of variance.

Table 1 summarizes the clinical characteristics of the patients. Most patients (n = 30, 83.3%) had early-onset disease.

Table 1

Baseline clinical and demographic characteristics of PN patients and healthy controls

Variables	Patients (n=36)	Controls (n=36)	P
Age at the time of enrolment (M±SD)	47.2±9.3	46.8±9.1	0.306
Age at disease onset (M±SD)	40.1±7.2	NA	NA
Male:Female ratio	19/17	19/17	NA
BMI (M±SD)	22.1±2.5	23.3±1.6	0.412
The Prurigo score (M±SD)	40.9±1.2	NA	NA
Duration of psoriasis in years (M±SD)	7.8±4.9	NA	NA

Table 2 displays comparison in candidates of plasma biomarkers between the PN patients and healthy control group. Plasma contents of cortisol, cortisone, and progesterone were significantly lower in patients compared with control group (ps < 0.05). In addition, lower plasma levels of the ratio of cortisone to cortisol (P < 0.001) and higher levels of the ratios of testosterone to cortisol (P < 0.05, P < 0.01, and P < 0.05) were observed in patients with PN.

Table 2

Comparison in candidates of plasma biomarkers between the PN patients and healthy controls

Bio-index	PN (n=36)	Controls (n=36)	Statistical values
F	311.6±125.6	350.6±107.1	F1, 68=2.863, ηp2=0.167, P=0.018
E	47.2±19.4	83.2±18.8	F1, 68=69.107, ηp2=0.504, P<0.001
T	8.3±6.2	5.9±6.8	F1, 68=2.440, ηp2=0.035, P=0.123
P	7.7±19.5	19.0±32.2	F1, 68=8.937, ηp2=0.080, P=0.017
DHEA	7.2±7.0	6.5±5.0	F1, 68=0.357, ηp2=0.005, P=0.552
E/F	0.16±0.06	0.25±0.07	F1, 68=34.584, ηp2=0.337, P<0.001
T/F	0.054±0.023	0.017±0.003	F1, 68=5.026, ηp2=0.069, P=0.028
DHEA/F	0.046±0.150	0.019±0.014	F1, 68=1.750, ηp2=0.025, P=0.190

F, cortisol; E, cortisone; T, testosterone; P, progesterone; DHEA, dehydroepiandrosterone; The contents of all the seven compounds in plasma were reported in ng/mL. The levels of the 8 plasma biomarkers were presented as mean±standard deviation (SD)

Table 3 shows between PN's the pruritus severity and contents of plasma steroids and their ratios among the PN patients. Plasma levels of cortisol, cortisone, E/F, and T/F ratios showed a statistically significant correlation with disease severity.

Table 3

Coefficients of partial correlations between PN’s the pruritus severity and contents of plasma steroids and their ratios among the PN patients (n=36)

Bio-index	PRUNOSI
F	-0.851***
E	-0.474**
P	-0.256
E/F	0.438**
T/F	0.460**

*P<0.05, **P<0.01, ***P<0.001. F, cortisol; E, cortisone; T, testosterone; P, progesterone; DHEA, dehydroepiandrosterone; PRUNOSI, the prurigo score; VAS, visual analogue scale; VRS, verbal rating scale; NRS, numerical rating scale; DLQI, dermatology life quality index. Very high correlation, r>0.7; high correlation, 0.5 < r < 0.7; moderate correlation, 0.3 < r < 0.5; weak correlation, r<0.3

In this study, four biomarkers from eight candidate biomarkers in plasma showed abnormal levels in the PN patients. To the best of our knowledge, it was the first investigation to verify the influence of PN on the two neuroendocrine systems including the HPA and HPG axes as well as on the interactions between two systems. Previous studies were confined only to the HPA axis showing abnormal activity in other skin diseases, such as chronic urticaria.[78] Moreover, four biomarkers out of the nine biomarkers showing the intergroup differences (i.e., cortisol, cortisone, and the ratios of cortisone and testosterone to cortisol) were founded to be correlated with PN symptoms, especially for the pruritus severity. The four biomarkers could be potential biomarkers to accurately and objectively assess the pruritus severity of PN. To the best of our knowledge, it was also the first attempt to screen sensitive biomarkers for objectively assessing the pruritus severity of PN. This study could provide valuable insights into the physiological mechanism of psychological responses involved in the pathogenesis of PN.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.