Evaluation of relationship between sexual functions, depression and quality of life in patients with chronic kidney disease at predialysis stage

Abstract

Aim: The relation of chronic kidney disease (CKD) with metabolic, psychiatric and endocrinologic disorder is well-known. Depressive mood and sexual dysfunction are frequently observed as renal functions deteriorate. We aimed to analyze the relationship of sexual dysfunction, depressive mood and life quality in patients with CKD at predialysis stage. Patients and methods: Fifty-three patients; 27 female and 26 male with CKD who had estimated glomerular filtration rate (eGFR) between 15 and 90 mL/min and followed up in the Nephrology Department, Bursa Sevket Yılmaz Education and Research Hospital, were enrolled. Age- and sex-matched 20 female and 20 male healthy control subjects were assigned to the control group. Detailed medical and sexual history was obtained by using Female Sexual Function Index (FSFI), Erectile Function International Evaluation Form (IEFF), Short form (SF) 36 Form and Beck Depression Questionnaire (BDI). Biochemical and hormonal parameters including urea, creatinine, uric acid, sedimentation rate, c-reactive protein, total testosterone, DHEA-S, FSH, LH, TSH, estradiol and prolactin were analyzed. Findings: Depression was observed in 12 male (46%) and 14 female (51%) patients. The frequency of depression among male patients and control subjects was similar, however, significantly higher in female patients than female controls (p = 0.036). Physical function score, physical role score and pain score in SF 36 of entire patients were significantly lower than controls (p = 0.0001, 0.0001, 0.001, respectively). The frequency of depression was similar between patients and controls (p > 0.05). When SF 36 tests of male and female patients were compared, general health status, vitality and mental health status were significantly better in male patients (p = 0.005, 0.016, 0.035, respectively). SF 36 scores of female patients were significantly lower than female controls (p = 0.0001). The frequency of erectile dysfunction (ED) was similar between male patients (84%) and controls (75%) (p = 0.62). On the other hand, sexual dysfunction was significantly higher in female patients when compared to female controls (92% vs. 30%; p = 0.0001). Conclusion: We showed that sexual dysfunction and depression are more frequent among female patients with CKD at predialysis stage; however, it does not have significant impact on life quality. When life quality of female and male patients was compared, general health status, vitality and mental health status of female patients were poorer. We failed to demonstrate a relationship between sexual dysfunction and sex hormone level.

• Chronic kidney disease
• predialysis stage
• sexual dysfunction
• depression
• life quality

Introduction

Chronic kidney disease (CKD) is defined as decrease of glomerular filtration rate (GFR) leading to progressive deterioration of fluid-electrolyte balance and metabolic or endocrinologic functions.1 The relation of CKD with hyperparathyroidism, infertility and sexual dysfunction is well-defined that affects medical health status as well as social, economic and physiological status.2

Sexuality is a source of human existence and complex process influenced by several factors including medical, psychological, sociocultural and economical.3 Lack of standardized terms exists due to inadequacy of understanding the pathophysiology of sexual dysfunction.4 Sexual dysfunction is a term that describes the lack of sexual desire accompanying sexual distress.5 Approximately, three quarters of male patients with CKD experience erectile dysfunction (ED).6 On the other hand, there is a wide range of frequency of sexual dysfunction among female patients with CKD; ranging from 30% to 100%.7 Variability of results between different populations may attribute to several factors including ethnicity and cultural differences. Yazici et al.7 reported that only 22% of patients with sexual dysfunction request for medical help.

Depression is usually related to loss of renal and sexual function, physical and intellectual capacity and social role. Psychiatric aspects of organ failure; especially depression, is widely studied among patients with CKD.8–10 Erectile dysfunction is related to decreased life quality, which is a risk factor for the development of depression.11 Additionally, depression is considered as an independent factor of sexual dysfunction; especially for male patients with CKD.12

Owing to the fact that CKD directly affects health related life quality index (HRLQi), evaluation of HRLQi is important to determine the morbidity and mortality rate of disease.13 So far, there is little data related to sexual dysfunction in predialysis stage of females and male patients with CKD, this study was aimed to assess sexual dysfunction of the patients and the relationship between disease activity, psychological status and quality of life.

Patients and methods

A total of 53 consecutive patients; 27 female and 26 male sexually active patients with CKD that had GFR between 15 and 90 mL/min, at Bursa Şevket Yılmaz Education and Research Hospital, Nephrology outpatient clinic between September 2011 and December 2011 and were recruited into the prospective case-control study. Age- and sex-matched 20 female and 20 male healthy subjects with regular sexual activity were assigned to the control group. Menopause ratio of female patients and controls were similar. Entire patients and control subjects were married. We excluded a number of patients and controls like sexually inactive, pregnant and individuals who do not accept gynecologic or urologic examination. Written consent was obtained from all participants. Ethics committee of Bursa Şevket Yılmaz Education and Research Hospital approved the study. All the subjects read and signed the informed consent forms before enrolling into the study.

Medical and sexual history of controls and patients were evaluated by Female Sexual Function Index (FSFI), Erectile Function International Evaluation Form (IEFF), Short form (SF) 36 Form and Beck Depression Inventory (BDI).14–17

For the assessment of sexual satisfaction, FSFI test was applied to all female patients who were described by Rosen et al.18; and includes the domains of sexual desire, arousal, lubrication, orgasm, satisfaction and pain during sexual intercourse. The overall score and subscores of sexual functional status in female patients and controls were calculated. Scale is negatively pointed to individuals who had sexual activity in last month and subgroups have different scores. Every question has scores between 0–5 and 1–5: lubrication (1–5 points), orgasmic function (1–5 points), sexual desire (2–10 points), satisfaction (2–10 points), clitoral sensitivity (1–5 points) and overall satisfaction (2–10 points).19 Total FSFI score <22.7 is considered as a sexual dysfunction. FSFI subgroups are multiplied by a coefficient as follows: lubrication 0.3, orgasmic function 0.4, sexual desire 0.6, stimulation 0.3, sexual pain 0.4 and sexual satisfaction 0.4. Sexual desire <3.6 is defined as low libido, stimulation score <3.9 is defined as impaired stimulation, lubrication score <3.6 is defined as impaired lubrication, orgasm score <3.6 is defined as impaired orgasm, sexual satisfaction score <3.6 impaired sexual satisfaction and sexual pain score <4 is defined as impaired sexual pain.20

All patients and controls were evaluated in terms of possible presence of depression with the BDI, and the cutoff point was accepted as 17. BDI is a self applicable test consisting of 21 questions that examine characteristic features and symptoms of depression like, sadness, self dislike, pessimism and fatigue. There are four options in 21 sign category. Every item has scores between 0 and 3. Depression score is sum of overall scores. High overall score reflects severity of depression. Maximum score is 63. Depression was defined as overall BDI score higher than 17. It was created by Beck et al. and validated to Turkish community.15

Short form 36 (SF-36) was introduced by Rand Corporation to assess life quality. It is composed of 36 items to analyze eight subjects: (1) Physical function; (2) social function; (3) role physical function; (4) emotional role function; (5) mental health; (6) healthiness; (7) pain; (8) general health status. Evaluation can be made by Likert type and includes last 4 week. Subscales range from 0 to100 and high scores indicate better life quality. SF 36 is supposed to evaluate life quality in persons with organic disorders. It is consist of 36 items that examine eight subgroups: (1) physical function; (2) social function; (3) role physical function; (4) emotional role function; (5) mental health; (6) crispness; (7) pain; (8) general health status. Evaluations are performed in Likert type and last 4 weeks are considered. Subscales are scored between 0 and 100, and high score reflects better life quality. It was reported that it can be used to evaluate life quality in patients with organic disorders.16 The scale of SF36 was shown.

IEFF evaluates male erectile function by 15 questions. These questions are: erectile function 6 questions, orgasm function 2 questions, sexual desire 2 questions, sexual satisfaction 3 questions and general satisfaction 2 questions. By 6 questions in erectile function subject (maximum score 30) IEFF classifies ED into four subgroups: nano (26–30 score), mild (22–25 score), mild-moderate (17–21 score), moderate (11–16 score) and severe (6–10 score). Erectile function score is calculated by answers: never or almost never - 1; rarely - 2; sometimes - 3; generally - 4; always - 5.15

Fasting blood samples were collected in early follicular phase of female patients and controls and at any time for male patients. Whole blood count, blood urea nitrogen, creatinine, uric acid, total protein, albumin, parathormone (PTH), C-reactive protein (CRP), sedimentation rate, high-density lipoprotein (HDL), low-density lipoprotein (LDL), aspartate transaminase (AST), alanine transaminase (ALT), sodium (Na), potassium (K), calcium (Ca), phosphorus (P), prolactin (PRL), luteinizing hormone (LH), follicle-stimulating hormone (FSH), dehydroepiandrosteredione sulfate (DHEA-SO₄), total testosterone, estradiol (E2) and thyroid stimulating hormone (TSH) were analyzed after centrifugated and stored at 80 °C. Biochemical parameters were analyzed by using an Aeroset autoanalyzer (Abbott Laboratories Inc., Abbott Park, IL). Plasma glucose levels were measured using the glucose oxidase method. Prolactin (4–15.2 ng/mL), total testosterone (2.5–8.36 ng/mL), DHEA-S (44.3–331 μg/dL), FSH (1–8 IU/L), LH (1–12 IU/L), TSH (0.3–4 μIU/mL) and E2 (7.63–42.6 pg/mL) levels were analyzed by Roche Hitachi Elecsys 2010 Immunoassay analyzer (Carnation, WA). Macroprolactin levels were measured with polyethylene glycol for patients with high PRL level. Biochemical and hormonal parameters were examined simultaneously with the study. MDRD formula was used to determine GFR (Glomerular filtration rate = 186 × Serum creatinine – 1.154 × age – 0.203 × gender × race).

Statistical analysis

SPSS 17.0 (SPSS Inc, Chicago, IL) package program was used for the statistical analysis. Data were expressed as mean ± SD. Parametric variables were compared using independent t-test, ordinal data were compared using Mann–Whitney U-test and non-parametric variables were compared using the chi-square test. Pearson’s correlation test was used to evaluate the relation between two parametric variables. A p value <0.05 was considered as significant.

Results

Mean duration of CKD was 24 ± 21 months in 53 patients (mean age was 55 ± 8.7 years). The mean duration of male and female patients were 23.4 ± 19.2 and 21.7 ± 15.4 months, respectively (p = 0.72). The mean age of male and female patients were 52.6 ± 7.1 and 49.1 ± 9.87, respectively (p = 0.59). The mean age and disease duration of male and female patients were similar. Control group consist of 20 female and 20 male individuals (mean age was 49.8 ± 6.6 years). The mean age of male and female controls were 51.3 ± 5.7 and 48.3 ± 7.22, respectively. Mean age of patients and controls were similar. Ratio of menopausal status of patients (33%) and controls (30%) were similar.

Depression was observed in 26 patients (50%); 12 male (46%) and 14 female (51%). There was a non-significant difference between patients and controls, in terms of depression frequency as well as between male and female participants (p = 0.054 and p = 0.78). We found no significant impact of age, duration of disorder, hypertension, diabetes mellitus and anemia on the frequency of depression (p > 0.05). There was no significant difference between patients and controls in terms of depression frequency. Additionally, frequency of depression was similar between male and female patients.

Patient group has significantly lower physical function, physical role, pain, social function, general health status, vitality, emotional role and mental health score when compared to control subjects (p = 0.0001, 0.0001, 0.001, 0.0001, 0.0001, 0.0001, 0.0001, 0.007, respectively). Impact of age, duration of disorder, hypertension, diabetes mellitus and anemia on SF36 scores was non-significant (p > 0.05).

The relation of pain with serum testosterone, total protein, HDL-cholesterol and AST were significant (p = 0.049, 0.011, 0.045, 0.027, respectively; r = 0.27, 0.34, 0.27, 0.30, respectively). Vitality was significantly related with total protein, total cholesterol, LDL-cholesterol and HDL-cholesterol (p = 0.008, 0.002, 0.02, 0.018, respectively and r = 0.36, 0.41, 0.32, 0.32, respectively). There was a significant relation between emotional role and serum albumin, uric acid and blood urea nitrogen (p = 0.035, 0.02, 0.011, respectively and r = 0.29, 0.31, 0.34, respectively). Mental health status was significantly related with serum testosterone, cholesterol and uric acid level (p = 0.04, 0.03, 0.027, respectively and r = 0.28, 0.29, 0.30, respectively). Serum uric acid level was significantly correlated to testosterone and prolactin level (p = 0.04, 0.014, respectively and r = 0.27, 0.33, respectively). Despite non-significant association between testosterone and PTH in all patients (p = 0.59; r = 0.07), association of DHEA-S and PRL with PTH were significant (p = 0.023, 0.006, respectively and r = 0.31, 0.37, respectively). Age was significantly correlated with DHEA-S, PRL, E2 and uric acid (p = 0.001, 0.044, 0.003, 0.047, respectively and r = 0.44, 0.27, 0.40, 0.27, respectively).

Physical function score, physical role, pain, general health status, vitality social function and emotional role of male and female patients were similar. General health, vitality, mental health status of male patients were significantly better than female patients (p = 0.005, 0.016, 0.035, respectively).

Testosterone levels of male and female patients were within the normal range. Serum LH, FSH and PRL levels of patients were significantly higher than control subjects. We observed no significant association between sexual dysfunction and testosterone or PRL level in male and female patients. Table 1 shows the comparison of biochemical and hormonal parameters of male patients and controls. Table 2 shows the comparison of biochemical and hormonal parameters of female patients and controls.

Table 1. Comparison of laboratory data of male patients and the control group.

	Patients group (n = 26)	Control group (n = 20)
	Mean ± SD	Mean ± SD	p
BUN (mg/dL)	48.35 ± 40.35	14.4 ± 3.36	0.001
Creatinine (mg/dL)	2.45 ± 1.38	0.91 ± 0.14	0.0001
Uric acid (mg/dL)	6.82 ± 1.33	5.6 ± 1.5	0.008
Total protein (g/dL)	7.48 ± 0.57	7.3 ± 0.39	0.19
Albumin (g/dL)	4.29 ± 0.48	4.72 ± 0.2	0.001
Hematocrit (%)	40.49 ± 4.37	44.3 ± 3.13	0.001
PTH	135.73 ± 133.4	46.4 ± 16.2	0.005
CRP (mg/L)	10.2 ± 11.3	4.0 ± 2.5	0.02
ESR (mm/saat)	21.46 ± 16.6	14.7 ± 7.7	0.1
Testosterone (ng/mL)	4.16 ± 1.26	4.43 ± 1.66	0.44
DHEA-S (µg/dL)	166.06 ± 120	142.49 ± 66.5	0.4
Estrogen (pg/mL)	35.7 ± 10	37.8 ± 20.7	0.68
TSH (µIU/mL)	1.65 ± 1.27	1.86 ± 1.15	0.56
FSH (IU/L)	8.31 ± 6.44	4.74 ± 2.08	0.02
LH (IU/L)	8.44 ± 4.8	5.07 ± 3.57	0.009
Prolactin (ng/mL)	10.03 ± 3.68	5.96 ± 2.20	0.0001
Calcium (mg/dL)	8.8 ± 9.1	8.9 ± 6.1	0.25
Phosphorus (mg/dL)	3.5 ± 1.4	3.2 ± 0.5	0.38

Table 2. Laboratory data of female patients and controls.

	Patients group (n = 26)	Control group (n = 20)
	Mean ± SD	Mean ± SD	p
BUN (mg/dL)	4.27 ± 26.7	12.7 ± 2.65	0.0001
Creatinine (mg/dL)	2.44 ± 1.29	0.67 ± 0.09	0.0001
Uric acid (mg/dL)	6.16 ± 1.75	4.4 ± 0.81	0.0001
Total protein (g/dL)	7.42 ± 0.52	7.28 ± 0.30	0.25
Albumin (g/dL)	4.25 ± 0.35	4.4 ± 0.25	0.02
Hematocrit (%)	34.5 ± 3.4	38.7 ± 2.68	0.0001
PTH	190.83 ± 136.34	54 ± 28	0.0001
CRP (mg/L)	9.06 ± 14.7	5.3 ± 5.6	0.002
ESR (mm/saat)	33 ± 15	23 ± 13	0.25
Testosterone (ng/dL)	0.24 ± 0.30	0.20 ± 0.09	0.51
DHEA-S (µg/dL)	105 ± 100	117 ± 71	0.61
Estrogen (pg/mL)	27.79 ± 28.1	34,4 ± 28.9	0.43
TSH (µIU/mL)	2.38 ± 1.43	1.41 ± 0.7	0.005
FSH (IU/L)	85.1 ± 41.9	73.7 ± 32.5	0.01
LH (IU/L)	50.06 ± 49	21.29 ± 13.9	0.007
Prolactin (ng/mL)	20.4 ± 19.9	10.2 ± 6.7	0.01
Phosphorus (mg/dL)	3.73 ± 0.59	3.37 ± 0.44	0.02
Calcium (mg/dL)	9.1 ± 0.6	9.1 ± 0.29	0.6

According to BDI, the frequency of depression in male patients (46%) and controls (35%) were similar (p = 0.55). According to IEFF, the frequency of ED in male patients [84%, n = 22 (mild 50%, moderate 32% and severe 18%)] and controls (75%, n = 15) were similar (p = 0.62). We found a non-significant association between ED and serum levels of sex hormones, age, duration of disorder, and the presence of hypertension or diabetes mellitus. When SF 36 scores of male patients and controls were considered, physical function score, physical role, general health status, vitality, social function and emotional role were significantly lower in male patients (Table 3).

Table 3. Quality of life and depression scores of male patients and controls.

	Patient group (n = 26)	Control group (n = 20)
	Mean ± SD	Mean ± SD	p
Age (years)	52.6 ± 7.1	51.3 ± 5.7	0.51
Physical function score	51.15 ± 21.4	81.5 ± 10.14	0.0001
Physical role score	50.96 ± 37	72.5 ± 22.79	0.03
Pain score	67 ± 25	74.5 ± 11.9	0.24
General health score	43.2 ± 15.2	73 ± 5	0.0001
Vitality score	61 ± 23	83.75 ± 6	0.0001
Socail function score	68.27 ± 24.81	93.75 ± 7.5	0.0001
Emotional role score	45.7 ± 27.64	74.65 ± 24	0.001
Mental health score	74 ± 20.46	77 ± 10	0.59
ED score	18.15 ± 5.75	16.9 ± 9.7	0.62
BDI score	15 ± 11	14 ± 10	0.55

The frequency of depression was significantly higher in female patients (n = 14, 51%) than female controls (n = 4, 20%) (p = 0.036). When SF 36 scores of female patients and controls were considered, physical function score, physical role, pain, general health status, vitality, social function, emotional role and mental health scores were significantly lower in female patients (Table 4).

Table 4. Quality of life and depression scores of female patients and controls.

	Patient group (n = 27)	Control group (n = 20)
	Mean ± SD	Mean ± SD	p
Age (years)	49.1 ± 9.87	48.3 ± 7.22	0.65
Physical function score	46.11 ± 17.96	85.25 ± 11.9	0.0001
Physical role score	48.4 ± 37.4	77.5 ± 24.1	0.002
Pain score	60 ± 26	74 ± 14.2	0.001
General health score	36.4 ± 17.1	73.4 ± 5.2	0.0001
Vitality score	52 ± 24	86 ± 5.9	0.0001
Social function score	67.6 ± 25.3	93.75 ± 7.5	0.0001
Emotional role score	47.6 ± 26.6	76.3 ± .22.1	0.001
Mental health score	66.9 ± 22.12	77 ± 10.6	0.002
BDI score	17 ± 11	10 ± 7	0.036

According to total FSFI score, sexual dysfunction was significantly frequent in female patients when compared to female controls (92%, n = 25 vs. 30%, n = 6; p = 0.0001). Subgroups of FSFI scoring system in female patients and controls were as follows: lack of sexual desire 55% (n = 15), impaired sexual arousal 77% (n = 21), impaired lubrication 44% (n = 12), difficulty in reaching orgasm 77% (n = 21), impaired sexual satisfaction 66% (n = 18), impaired sexual pain 74% (n = 20), respectively. In the control group, FSFI scores were as follows: lack of sexual desire 10% (n = 2), impaired sexual arousal 40% (n = 8), impaired lubrication 0% (n = 0), difficulty in reaching orgasm 10% (n = 3), impaired sexual satisfaction 15% (n = 3), impaired sexual pain 10% (n = 2) (Table 5). In female patients group, the relation of FSFI with age, duration of disorder and the presence of hypertension or diabetes mellitus were non-significant. FSFI score was significantly related to serum FSH (p = 0.011; r = 0.48).

Table 5. Comparison of female sexual function indexes and components.

	Patients group (n = 26)	Control group (n = 20)
	Mean ± SD	Mean ± SD	p
FSFI total score	20.15 ± 4.23	27.3 ± 1.99	0.0001
Sexual desire score	4.5 ± 1.1	4.62 ± 0.91	0.01
Libido score	3.2 ± 1.5	4.3 ± 0.6	0.03
Lubrication score	2.93 ± 1.91	4.49 ± 0.65	0.0001
Sexual satisfaction score	2.6 ± 1.8	4.3 ± 0.6	0.0001
Orgasm score	3.14 ± 1.26	4.12 ± 0.62	0.0001
Pain score	3.10 ± 1.7	5.5 ± 0.7	0.0001

Discussion

The present study indicated that in contrast to male patients with CKD, female patients with CKD have significantly higher incidence of sexual dysfunction, depressive mood and poor life quality.

In the present study, ED was observed in 42% by interviewing with patient and 84% by IEFF beside 23% of patients had testicular atrophy in urologic examination. The frequency of ED in our study was significantly higher than previous studies that were carried out in patients on renal replacement therapy (RRT). The other interesting result of the study was that only 20% of our patients with ED request medical help that supports the role of sexual monomania.

The relation of ED with testosterone is well-documented by the “Massachusetts Male Aging Study”. In contrast to the previous report, we failed to demonstrate relation between serum testosterone level and ED scores.21 ED has two cornerstones: hormonal deficiency and behavioral disorder, which are a possible explanation of our controversial result. The complex interaction of sexual dysfunction, quality of life and depression is generally underestimated. Inadequate sexual performance may lead to anxiety, lack of sexual desire and even depression.

Similar to our results, sexual dysfunction is frequently observed among patients with CKD.22 Some recent studies revealed out that the frequency of ED may reach to 40–75% in uremic males.23 Fryckstedt et al.24 determined that male and female patients with CKD have similar frequencies of sexual dysfunction. Among healthy male individuals, sexual dysfunction has been reported to be 20–80%.25^,26 Similar to our control group, Akkus et al.27 showed that the frequency of ED was 69.2% in 1982 male individuals from Turkey. A non-significant difference between male patients and controls in terms of ED scores emphasized that male patients with CKD at predialysis stage have similar sexual functions to healthy population.

Kurdoglu et al.28 evaluated the Arizona Sexual Experiences Scale, BDI and endogenous gonadotropin levels in female patients at predialysis stage and on hemodialysis (HD) and established that patients at predialysis stage exhibit depressive symptoms, 6- and 3.8-fold frequently when compared to healthy controls and patients on HD. In the same study, patients with depressive symptoms at predialysis stage have 24-fold increased risk of sexual dysfunction than patients without depressive symptoms. Increased frequency of depressive symptoms at predialysis is probably attributed to fear receiving dialysis therapy and becoming dependent on renal replacement modalities. We determined that sexual dysfunction was significantly more frequent among female patients at predialysis stage and the most frequent problems were impaired sexual arousal and orgasm. Hormonal alterations in menopause stage may affect sexual functions.29 However, we matched female patients and controls with regard to frequency of menopausal stage to exclude the impact of menopause on sexual functions. Sexual dysfunction is observed in 22–93% of healthy women and prevalence increases by aging.30 Similarly, previous studies from Turkey showed that 30% of healthy women have sexual dysfunction.3^,31

A number of studies pointed out those lower urinary tract infections comprise risk for sexual dysfunction.30^,31 Lower urinary infection was observed in 74% of our female patients and 35% control subjects. We found no significant relation between FSFI score and lower urinary tract infection.

House32 followed-up 80 patients with CKD for 1 year and observed psychiatric disorder in 30%. Kimmel et al.33 conducted a study in patients on HD for 1 year and showed that 10% of patients have at least one psychiatric disorder. In a study from Turkey, 16 of 70 patients (22.9%) on HD had at least one psychiatric disorder.34 Depression is related to decrease of sexual interest and desire.35 Our male patients at predialysis stage and male controls have similar depression rates. Although depression was more frequent in female patients, it has no significant impact on sexual dysfunction. Non-significant relation of depression and sexual dysfunction in our study is attributed to short duration of disorder and high GFR that reflects well preserved renal functions.

Rate of depression is 10% in Turkish population without an accompanying disorder.36 Higher frequency of depression among our control subjects (female 20% and male 35%; overall 27%) is a possible explanation for controversial results.

Although testosterone levels were within normal range and serum LH, FSH and PRL were significantly higher than controls, we found no significant association between sexual dysfunction and serum testosterone and PRL levels. PRL levels were higher than upper limit of normal range, however, macroprolactin was negative in entire patients. Similar to our results, Toorians et al.37 observed no significant correlation between sexual dysfunction and biochemical parameters including urea and creatinine. In contrast to our study, some researchers concluded that higher PTH level may lead to a decrease in testosterone.38

Mittal et al.39 stated that men have higher physical function score than women however mental function scores were similar. Several studies from different populations demonstrated no significant difference between men and women in terms of life quality.40^,41 In contrast, we found that male patients with CKD have better general health, vitality and mental health scores, similar to the study by Ogutmen et al.42^,43

Fujısawa et al.41 and Balaska et al.44 reported that life quality scores of younger patients were better than elder patients. On contrary, Patton et al.45 and Humar et al.46 demonstrated that there was no significant association between age and life quality. Shu-Fen et al.47 showed that age is the most significant determinant of life quality. We demonstrated no significant role of age, duration of disease, hypertension, diabetes mellitus, depression, sexual dysfunction and anemia on life quality, which is explained by short duration of CKD and mild elevation of creatinine level.

Our study has some limitations. First, number of sample size was relatively low which limits the statistical significance. Second, there may be several factors interacting with sexual dysfunction like medical therapy, family history, educational status and vascular abnormalities. Third, low adherence of participants to questionnaire due to social issues and inadequate communication of physician and participants may cause underestimation of true relationship of CKD and sexual dysfunction. Finally, our population consists of Turkish patients on predialysis stage that inhibit to generalize our results to other races.

There are a limited number of studies concerning sexual dysfunction in female patients at predialysis stage. Medical status, disease activity, physiologic abnormalities, hormonal disturbances, psychiatric status and family history should be considered in the evaluation of sexual dysfunction. The importance of the present study is that it is one of a few reports examining the interaction of sexual dysfunction, life quality, and depression and sex hormone levels in patients at predialysis stage in both sexes. Also, similar frequencies of depression among patients and controls excluded the role of depression on sexual functions.

In conclusion, sexual functions are an important stressor which is inadequately evaluated. Sexual dysfunction should be considered and questioned in CKD patients at predialysis stage; especially in female patients. In the presence of sexual dysfunction, disease activity and depression should be evaluated as well as physical examination and endocrinologic assessment. Further studies with large number of participants are required to reach more precise conclusion.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.