Serum levels of human growth hormone during different penile conditions in the cavernous and systemic blood of healthy men and patients with erectile dysfunction

Erectile function and androgen and estrogen beta receptor gene polymorphisms in acromegalic men

PURPOSE

Sexual dysfunctions are often experienced by male patients with acromegaly, due to a combination of hypogonadism and other comorbidities, but are a scarcely investigated complication. Erectile dysfunction is also closely related to cardiovascular diseases through endothelial dysfunction. Therefore, this project aimed to assess the prevalence of erectile dysfunction in a population of acromegalic men and evaluate its association with cardio-metabolic disorders, also exploring associations with androgen and estrogen receptor gene polymorphisms.

METHODS

Sexually active men aged 18-65 with previous diagnosis of acromegaly were recruited. Clinical and laboratory data were retrospectively collected. Each patient also provided a blood sample for AR and ERβ gene polymorphisms analyses and filled out the IIEF-15 questionnaire.

RESULTS

Twenty men with previous diagnosis of acromegaly (mean age 48.4 ± 10.0 years) were recruited. 13/20 subjects (65%) had erectile dysfunction, but only four had a concurrent biochemical hypogonadism, with no significant correlation with IIEF-15 scores. Total testosterone negatively correlated with sexual intercourse satisfaction domain (ρ = - 0.595; p = 0.019) and general satisfaction domain (ρ = - 0.651; p = 0.009). IGF-1 levels negatively correlated with biochemical hypogonadism (ρ = - 0.585; p = 0.028). The number of CAG and CA repeats in AR and ERβ receptors genes was not significantly associated with IIEF-15 scores or with GH/IGF-1 levels, but a negative correlation between CA repeats and the presence of cardiomyopathy (ρ = - 0.846; p = 0.002) was present.

CONCLUSIONS

Men with acromegaly have a high prevalence of erectile dysfunction, but it does not appear to be correlated with treatments, testosterone levels and AR/ER-beta signaling. Nonetheless, a shorter CA polymorphic trait (ERbeta) is associated with the presence of cardiomyopathy. If confirmed, these data may suggest an association between an incorrect hormonal balance and increased cardiovascular risk in acromegaly subjects.

Effects of Growth Hormone on Adult Human Gonads: Action on Reproduction and Sexual Function

Growth hormone (GH), which is commonly considered to be a promoter of growth and development, has direct and indirect effects on adult gonads that influence reproduction and sexual function of humans and nonhumans. GH receptors are expressed in adult gonads in some species including humans. For males, GH can improve the sensitivity of gonadotropins, contribute to testicular steroidogenesis, influence spermatogenesis possibly, and regulate erectile function. For females, GH can modulate ovarian steroidogenesis and ovarian angiogenesis, promote the development of ovarian cells, enhance the metabolism and proliferation of endometrial cells, and ameliorate female sexual function. Insulin-like growth factor-1 (IGF-1) is the main mediator of GH. In vivo, a number of the physiological effects of GH are mediated by GH-induced hepatic IGF-1 and local IGF-1. In this review, we highlight the roles of GH and IGF-1 in adult human gonads, clarify potential mechanisms, and explore the efficacy and the risk of GH supplementation in associated deficiency and assisted reproductive technologies. Besides, the effects of excess GH on adult human gonads are discussed as well.

Diagnostic work up: Laboratory and biomarkers

This chapter will focus on the diagnostic work around sexual dysfunction in Parkinson's disease, especially laboratory tests and biomarkers. A number of methods to analyze if sexual dysfunction is caused by neural pathology, vascular dysfunction or other mechanisms are now available. Other methods can be used to differentiate between psychogenic/functional reasons behind sexual dysfunction and organic ones. The role of biomarkers for diagnosis, but also for understanding the reason behind and for counteracting sexual dysfunction is becoming more evident. There is also a rich and increasing number of scales and other instruments available for detecting and quantifying sexual hypo- and hyperactivity. When investigating the reason behind sexual dysfunction in patients with Parkinson's disease comorbidities should also be considered. Finally, early and pronounced sexual dysfunction might in some cases be an indication that differential diagnosis, like Multisystem Atrophy, should be thought about. All these aspects of the diagnostic procedures around sexual dysfunction in Parkinson's disease will be covered in this chapter.

Hypothalamic-Pituitary Diseases and Erectile Dysfunction

Several hormones contribute to ensure penile erection, a neurovascular phenomenon in which nitric oxide plays a major role. Erectile dysfunction (ED), which is defined as the persistent inability to obtain or maintain penile erection sufficient for a satisfactory sexual performance, may be due to arteriogenic, neurogenic, iatrogenic, but also endocrinological causes. The hypothalamus-pituitary axis plays a central role in the endocrine system and represents a fundamental link between the brain and peripheral glands, including gonads. Therefore, the hormonal production of the hypothalamic-pituitary axis can control various aspects of sexual function and its dysregulation can compromise erectile function. In addition, excess and deficiency of pituitary hormones or metabolic alterations that are associated with some pituitary diseases (e.g., Cushing's disease and acromegaly, hypopituitarism) can determine the development of ED with different mechanisms. Thus, the present review aimed to explore the relationship between hypothalamic and pituitary diseases based on the most recent clinical and experimental evidence.

Sexual Dysfunction: A Neglected and Overlooked Issue in Adult GH Deficiency: The Management of AGHD Study

Context

Although sexuality influences well-being and quality of life (QoL), studies on sexual dysfunction (SD) in adult growth hormone deficiency (AGHD) patients are lacking.

Objective

To investigate the prevalence of SD in AGHD patients grouped according to recombinant human growth hormone (r-hGH) therapy.

Design

Prospective, cross-over, 24 months, monocentric study.

Setting

Real-life clinical setting in a tertiary, endocrinological center.

Patients

83 AGHD patients (31 women, 52 men, mean age 56.3 ± 14.7 years) were enrolled according to stringent criteria.

Intervention(s)

Patients already on long-term r-hGH therapy (Group 1, n = 32) vs untreated (Group 2, n = 51).

Main outcome measure(s)

Serum hormones, QoL Satisfaction in Hypopituitarism (QLS-H) and QoL Assessment of GHD in Adults (QoL-AGHDA) questionnaires for QoL, Index for Erectile Function-15 (IIEF-15) in men, and Female Sexual Function Index (FSFI) in women for SD.

Results

The overall prevalence of SD was 71.2% (60% men, 89% women). All IIEF-15 scores were lower (P = 0.001) and erectile dysfunction was more prevalent in Group 2 (75%) than Group 1 (35%). IGF-1 was correlated to scores of all IIEF-15 domains, particularly with that of erectile function (EF) (R²=0.123, P = 0.019). EF domain score correlated with QLS-H (P < 0.005) and QoL-AGHDA (P = 0.001). Despite the high prevalence of female SD also in untreated AGHD women, FSFI scores did not correlate with IGF-1 levels and QoL scores.

Conclusions

SD is highly prevalent in AGHD patients, especially in those untreated. SD represents an overlooked and neglected issue in AGHD, regardless the contribution of sexual life on QoL. The evaluation of sexual function should be integrated in the global assessment of AGHD patients.

Somatotropic-Testicular Axis: A crosstalk between GH/IGF-I and gonadal hormones during development, transition, and adult age

BACKGROUND

The hypothalamic-pituitary-gonadal (HPG) and hypothalamic-pituitary-somatotropic (HPS) axes are strongly interconnected. Interactions between these axes are complex and poorly understood. These interactions are characterized by redundancies in reciprocal influences at each level of regulation and the combination of endocrine and paracrine effects that change during development.

OBJECTIVES

To comprehensively review the crosstalk between the HPG and HPS axes and related pathological and clinical aspects during various life stages of male subjects.

MATERIALS AND METHODS

A thorough search of publications available in PubMed was performed using proper keywords.

RESULTS

Molecular studies confirmed the expressions of growth hormone (GH) and insulin-like growth factor-I (IGF-I) receptors on the HPG axis and reproductive organs, indicating a possible interaction between HPS and HPG axes at various levels. Insulin growth factors participate in sexual differentiation during fetal development, indicating that normal HPS axis activity is required for proper testicular development. IGF-I contributes to correct testicular position during minipuberty, determines linear growth during childhood, and promotes puberty onset and pace through gonadotropin-releasing hormone activation. IGF-I levels are high during transition age, even when linear growth is almost complete, suggesting its role in reproductive tract maturation. Patients with GH deficiency (GHD) and insensitivity (GHI) exhibit delayed puberty and impaired genital development; replacement therapy in such patients induces proper pubertal development. In adults, few studies have suggested that lower IGF-I levels are associated with impaired sperm parameters.

DISCUSSION AND CONCLUSION

The role of GH-IGF-I in testicular development remains largely unexplored. However, it is important to evaluate gonadic development in children with GHD. Additionally, HPS axis function should be evaluated in children with urogenital malformation or gonadal development alterations. Correct diagnosis and prompt therapeutic intervention are needed for healthy puberty, attainment of complete gonadal development during transition age, and fertility potential in adulthood.

Endocrinologic Control of Men's Sexual Desire and Arousal/Erection

INTRODUCTION

Several hormones and neurotransmitters orchestrate men's sexual response, including the appetitive (sexual desire) and consummative (arousal and penile erection) phases.

AIM

To provide an overview and recommendations regarding endocrinologic control of sexual desire and arousal and erection and their disturbances.

METHODS

Medical literature was reviewed by the subcommittee of the International Consultation of Sexual Medicine, followed by extensive internal discussion, and then public presentation and discussion with other experts. The role of pituitary (prolactin, oxytocin, growth hormone, and α-melanocyte-stimulating hormone), thyroid, and testicular hormones was scrutinized and discussed.

MAIN OUTCOME MEASURES

Recommendations were based on grading of evidence-based medical literature, followed by interactive discussion.

RESULTS

Testosterone has a primary role in controlling and synchronizing male sexual desire and arousal, acting at multiple levels. Accordingly, meta-analysis indicates that testosterone therapy for hypogonadal individuals can improve low desire and erectile dysfunction. Hyperprolactinemia is associated with low desire that can be successfully corrected by appropriate treatments. Oxytocin and α-melanocyte-stimulating hormone are important in eliciting sexual arousal; however, use of these peptides, or their analogs, for stimulating sexual arousal is still under investigation. Evaluation and treatment of other endocrine disorders are suggested only in selected cases.

CONCLUSION

Endocrine abnormalities are common in patients with sexual dysfunction. Their identification and treatment is strongly encouraged in disturbances of sexual desire and arousal.

Erectile Dysfunction is Common among Men with Acromegaly and is Associated with Morbidities Related to the Disease

INTRODUCTION

The prevalence of erectile dysfunction (ED) and its correlates in men with acromegaly has never been investigated.

AIM

The aim of this study was to evaluate sexual function in men with acromegaly.

METHODS

Multicenter-based, retrospective analysis of a nonselected series of 57 acromegalic subjects (mean age: 52.7 ± 14.2 years) was performed. Acromegalic subjects reporting ED (n = 24) were compared with matched ED patients without acromegaly or pituitary disease (controls), selected from a cohort of more than 4,000 subjects enrolled in the Florence Sexual Medicine and Andrology Unit.

MAIN OUTCOME MEASURES

Patients were interviewed using Structured Interview on Erectile Dysfunction (SIEDY) structured interview, a 13-item tool for the assessment of ED-related morbidities. Several clinical and biochemical parameters were taken. Penile color Doppler ultrasound (PCDU) was performed in a subgroup of 37 acromegalic subjects.

RESULTS

ED was reported by 42.1% of acromegalic subjects. After adjusting for age and testosterone, acromegalic subjects with ED had a higher prevalence of hypertension and more often reported an impairment of sleep-related erections and a longer smoking habit. Accordingly, acromegaly-associated ED was characterized by a higher organic component and worse PCDU parameters. No relationship between ED and testosterone levels or other acromegaly-related parameters was found. However, acromegalic subjects with severe ED reported a longer disease duration. In a case-control analysis, comparing acromegalic subjects with ED-matched controls free from acromegaly (1:5 ratio), acromegalic men had a worse ED problem and a higher organic component of ED, as derived from SIEDY score. In line with these data, acromegalic patients with ED had a higher prevalence of major adverse cardiovascular events history at enrollment and lower PCDU parameters.

CONCLUSIONS

Subjects with complicated acromegaly are at an increased risk of developing ED, especially those with cardiovascular morbidities. Our data suggest including a sexual function evaluation in routine acromegaly follow-up.

Growth hormone and reproduction: a review of endocrine and autocrine/paracrine interactions

The somatotropic axis, consisting of growth hormone (GH), hepatic insulin-like growth factor I (IGF-I), and assorted releasing factors, regulates growth and body composition. Axiomatically, since optimal body composition enhances reproductive function, general somatic actions of GH modulate reproductive function. A growing body of evidence supports the hypothesis that GH also modulates reproduction directly, exerting both gonadotropin-dependent and gonadotropin-independent actions in both males and females. Moreover, recent studies indicate GH produced within reproductive tissues differs from pituitary GH in terms of secretion and action. Accordingly, GH is increasingly used as a fertility adjunct in males and females, both humans and nonhumans. This review reconsiders reproductive actions of GH in vertebrates in respect to these new conceptual developments.

Growth hormone, prolactin, and sexuality

GH and PRL, although not considered as 'classi cal' sexual hormones, could play a role in the endocrine control of sexual function both in men and women. Physiologically, PRL seems to be involved in the central control of sexual behavior and activity, by modulating mainly the effects of dopaminergic and serotoninergic systems on sexual function. Indeed, circulating PRL levels increase after orgasm and may potentially play a role in the acute regulation of further sexual arousal following orgasm both in men and women. On the other hand, either short-term or long-term PRL in crease can modulate central nervous system areas involved in the control of sexual function and, peripherally, can directly influence mechanisms of penile erection in men, and presently only as an hypothesis, mechanisms related to the sexual response of genitalia in women. Furthermore, chronic hyperprolactinemia is classically associated with hypogonadotropic hypogonadism and sexual dysfunction in both sexes. Successful treatment of chronic hyperprolactinemia generally restores normal sexual function both in men and women although this effect is not only related to relapse of gonadal function. Hypoprolactinemia is recently recognised as a possible risk factor of arteriogenic erectile dysfunction while a possible role on female sexual function is not known. The physiological role of GH on sexual function is not fully elucidated. GH is an important regulator of hypothalamus-pituitary-gonadal axis and seems to participate in the regulation of the sexual response of genitalia in men, and potentially also in women. Sexual function in men and women with GH deficiency (GHD) and GH excess, particularly in acromegaly, is scantily studied and GH- or IGF-I-dependent effects are difficult to quantify. Nevertheless, a decrease of desire and arousability both in men and women, together with an impairment of erectile function in men, have been described both in patients with GHD and acromegaly, although it is not clear whether they are dependent directly on the hormone defect or excess or they are consequence of the hypogonadism or the different clinical complications or the physical disfigurement and psychological imbalance, which are associated with the diseases, and are potentially affecting sexual function. Data on beneficial effects of GH replacement therapy and specific surgical or pharmacological approach for acromegaly are far to be fully elucidated although restoring normal GH/IGF-I levels have been associated to improvement of sexual function.

Hormonal causes of male sexual dysfunctions and their management (hyperprolactinemia, thyroid disorders, GH disorders, and DHEA)

INTRODUCTION

Besides hypogonadism, other endocrine disorders have been associated with male sexual dysfunction (MSD).

AIM

To review the role of the pituitary hormone prolactin (PRL), growth hormone (GH), thyroid hormones, and adrenal androgens in MSD.

METHODS

A systematic search of published evidence was performed using Medline (1969 to September 2011). Oxford Centre for Evidence-Based Medicine-Levels of Evidence (March 2009) was applied when possible.

MAIN OUTCOME MEASURES

The most important evidence regarding the role played by PRL, GH, thyroid, and adrenal hormone was reviewed and discussed.

RESULTS

Only severe hyperprolactinemia (>35 ng/mL or 735 mU/L), often related to a pituitary tumor, has a negative impact on sexual function, impairing sexual desire, testosterone production, and, through the latter, erectile function due to a dual effect: mass effect and PRL-induced suppression on gonadotropin secretion. The latter is PRL-level dependent. Emerging evidence indicates that hyperthyroidism is associated with an increased risk of premature ejaculation and might also be associated with erectile dysfunction (ED), whereas hypothyroidism mainly affects sexual desire and impairs the ejaculatory reflex. However, the real incidence of thyroid dysfunction in subjects with sexual problems needs to be evaluated. Prevalence of ED and decreased libido increase in acromegalic patients; however, it is still a matter of debate whether GH excess (acromegaly) may create effects due to a direct overproduction of GH/insulin-like growth factor 1 or because of the pituitary mass effects on gonadotropic cells, resulting in hypogonadism. Finally, although dehydroepiandrosterone (DHEA) and its sulfate have been implicated in a broad range of biological derangements, controlled trials have shown that DHEA administration is not useful for improving male sexual function.

CONCLUSIONS

While the association between hyperprolactinemia and hypoactive sexual desire is well defined, more studies are needed to completely understand the role of other hormones in regulating male sexual functioning.

The future of the oral pharmacotherapy of male erectile dysfunction: things to come

The convincing clinical data on the use of the orally active phosphodiesterase inhibitors sildenafil, vardenafil and tadalafil for the treatment of male erectile dysfunction have boosted research activities on the physiology of the male erectile mechanism. This included both peripheral intracellular signal transduction in the corpus cavernosum as well as central brain and spinal cord pathways controlling penile erection. This work provided the basis for the development and introduction of several new therapeutic modalities into the management of erectile dysfunction, some of which are already offered to the patients. As the concept of 'taking a pill' as a cure for an illness or the relief of symptoms of a disease has become widely accepted by the consumers, the pharmacologic treatment of erectile dysfunction has primarily focussed on selective, orally available drugs acting by influencing intracellular or central regulatory mechanisms, combining a high response rate and the advantage of an on-demand intake. These agents are regarded as more efficacious, and have a faster onset of drug action in the target tissue and an improved effect to side-effect ratio. The purpose of this review is to describe the major novel and evolving pharmacologic advances in the field of oral pharmacotherapy for the treatment of male erectile dysfunction.

Molecular endocrinology and physiology of the aging central nervous system

Aging is associated with a progressive decline in physical and cognitive functions. The impact of age-dependent endocrine changes regulated by the central nervous system on the dynamics of neuronal behavior, neurodegeneration, cognition, biological rhythms, sexual behavior, and metabolism are reviewed. We also briefly review how functional deficits associated with increases in glucocorticoids and cytokines and declining production of sex steroids, GH, and IGF are likely exacerbated by age-dependent molecular misreading and alterations in components of signal transduction pathways and transcription factors.

Role of some vasoactive mediators in patients with erectile dysfunction: their relationship with angiotensin-converting enzyme and growth hormone

The imbalance between vasoconstrictors and vasodilators may play an important role in the pathogenesis of erectile dysfunction (ED). A total of 36 patients with ED, organogenic [diabetic (n=12) and nondiabetic (n=12)] and psychogenic (n=12) etiology, and 12 healthy adult men as controls were included. The levels of endothelin-1 (ET-1), growth hormone (GH), angiotensin-converting enzyme activity (ACE), nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) were determined in the flaccid penis cavernosal blood of patients and in cubital blood of patients and controls. In psychogenic ED, systemic ACE activity was elevated compared to controls (P<0.05). In diabetic and nondiabetic ED patients, systemic levels of ET-1 (P<0.0001 for both) and ACE activity (P<0.01 and <0.05) were higher while GH (P<0.0001 and <0.001), NO (P<0.0001 for both) and cGMP (P<0.01 for both) levels were lower compared to controls. In diabetic patients, systemic and cavernosal ET-1 levels (P<0.0001 for both) and cavernosal ACE activity levels (P<0.05) were significantly elevated while systemic and cavernosal NO (P<0.0001 for both) and GH (<0.001 and <0.05) levels were declined compared to psychogenic. In nondiabetic patients, systemic and cavernosal ET-1 levels (P<0.0001 for both) were significantly elevated while systemic and cavernosal NO (P<0.0001 for both) and systemic GH levels (P<0.05) were declined compared to psychogenic. Systemic NO was positively correlated with GH in psychogenic (r=0.616, P<0.05), diabetic (r=0.583, P<0.05) and nondiabetic (r=0.615, P<0.05) patients and correlated positively with cGMP (r=0.605, P<0.05) but negatively with ACE activities (r=-0.585, P<0.05) in diabetic patients. In conclusion, plasma levels of ET-1, ACE activities are elevated and associated with reduction of GH, NO and cGMP levels in the systemic and cavernous blood of ED patients. This disturbance may indicate endothelial dysfunction that may hind at their significance in the pathophysiology of ED.

The Consequences of Altered Somatotropic System on Reproduction1

Although the primary control of gonadotropin secretion is by the hypothalamic GnRH and the gonadal function is controlled by the pituitary gonadotropins and prolactin, the emerging evidence suggests a vital role of the somatotropic axis, growth hormone (GH), and insulin-like growth factor-I (IGF-I) in the control of the pituitary and gonadal functions. It has been shown that GH deficiency, GH resistance, and experimental alterations in IGF-I secretion modify folliculogenesis, ovarian maturation, ovulation, and pregnancy, and in the male, GH/IGF-I plays an important role in spermatogenesis and the Leydig cell function. The primary focus of this review is to examine the role of GH/ IGF-I on the onset of puberty, fertility, pituitary, and gonadal endocrine functions. A number of studies have revealed that fertility is affected in GH-deficient dwarf and in IGF-I gene-ablated mice, possibly due to subnormal function of either the pituitary gland or the gonads. In the female GH receptor gene knockout (GHR-KO) mice, there was impairment in follicular development, ovulation rate, sexual maturation, production of and responsiveness to pheromonal signals, and the corpus luteum function. In IGF-I-deficient male GHR-KO mice, puberty is delayed, spermatogenesis is affected, and neuroendocrine-gonadal function is attenuated. Similarly, in some of the human Laron syndrome patients, puberty is delayed due to GH resistance. These data suggest that, in addition to GnRH and gonadotropins, GH/IGF-I influences the pituitary and gonadal functions in animals and humans.

Current and future trends in the oral pharmacotherapy of male erectile dysfunction

The promising clinical data on the use of the first orally active phosphodiesterase inhibitor sildenafil citrate (Viagra) for treatment of male erectile dysfunction have been accompanied by an increase in research activities on the physiology of the male erectile mechanism. This included both peripheral intracellular signal transduction in the corpus cavernosum as well as central brain and spinal cord pathways that control penile erection. This work provided the basis for the development and introduction of several new therapeutic modalities into the management of erectile dysfunction that is now offered to the patients. Since the concept of 'taking a pill' as a cure for an illness or the relief of symptoms of a disease has become widely accepted by consumers, the pharmacological treatment of erectile dysfunction has primarily focused on selective, orally available drugs that act via influencing intracellular or central regulatory mechanisms, combining a high response rate and the advantage of an 'on-demand' intake. These agents are regarded as more efficacious, have a faster onset of drug action in the target tissue and an improved effect-to-side effect ratio than sildenafil. The purpose of this review is to describe the major novel and evolving pharmacological advances in the field of oral pharmacotherapy for the treatment of male erectile dysfunction.

Endocrine causes of impotence (nondiabetes)

The endocrine system has a major role in erections in normal men and it can also be a cause of significant morbidity. The relationship between serum testosterone measurement and erectile function is complex. Androgen treatment should certainly be considered in patients without prostate cancer but with a clinical picture that suggests a relevant contribution of hypogonadism to the ED. Other, nondiabetic, endocrine abnormalities may need to be considered in the management or the patient with ED.