Neuroendocrine abnormalities in Parkinson's disease.

Neuroendocrine abnormalities are common in Parkinson's disease (PD) and include disruption of melatonin secretion, disturbances of glucose, insulin resistance and bone metabolism, and body weight changes. They have been associated with multiple non-motor symptoms in PD and have important clinical consequences, including therapeutics. Some of the underlying mechanisms have been implicated in the pathogenesis of PD and represent promising targets for the development of disease biomarkers and neuroprotective therapies. In this systems-based review, we describe clinically relevant neuroendocrine abnormalities in Parkinson's disease to highlight their role in overall phenotype. We discuss pathophysiological mechanisms, clinical implications, and pharmacological and non-pharmacological interventions based on the current evidence. We also review recent advances in the field, focusing on the potential targets for development of neuroprotective drugs in Parkinson's disease and suggest future areas for research.

Effects of long-term oral testosterone undecanoate therapy on urinary symptoms: data from a 1-year, placebo-controlled, dose-ranging trial in aging men with symptomatic hypogonadism.

BACKGROUND: There has been a longstanding question as to whether testosterone therapy could precipitate or worsen urinary symptoms in aging men. We investigated the effects of 1-year oral testosterone undecanoate (TU) therapy on urinary symptoms in aging, hypogonadal men. METHODS: A total of 322 men ≥50 years with symptomatic testosterone deficiency participated in a 1-year, randomized, multicenter, double-blind trial. Patients received placebo or oral TU 80 mg/day, 160 mg/day, or 240 mg/day. RESULTS AND LIMITATIONS: Compared with placebo, treatment with oral TU at doses of 80 mg/day and 160 mg/day resulted in no significant change in IPSS urinary symptoms or quality of life (QoL) scores. Treatment with oral TU 240 mg/day led to a statistically significant, but clinically insignificant, improvement in IPSS total score and a significant improvement in IPSS QoL score. None of the TU doses tested had a significant effect on PSA or PV. CONCLUSIONS: Long-term oral TU therapy had no deleterious effects on IPSS total score and did not change PV and PSA in aging, hypogonadal men. Oral TU therapy at a dose of 240 mg/day may even improve IPSS QoL score.

Effects of oral testosterone undecanoate therapy on bone mineral density and body composition in 322 aging men with symptomatic testosterone deficiency: a 1-year, randomized, placebo-controlled, dose-ranging study.

OBJECTIVE: We investigated the effects of oral testosterone undecanoate (TU) on bone mineral density (BMD), lean body mass (LBM) and body fat mass (BFM) in aging men with symptomatic testosterone deficiency (TD). METHODS: Three hundred twenty-two men ≥50 years with TD symptoms and calculated free testosterone <0.26 nmol/L participated in a multicenter, double-blind, placebo-controlled trial. Patients were randomized to placebo, oral TU 80 mg/d, oral TU 160 mg/d, or oral TU 240 mg/d, administered as divided doses with normal meals. BMD of the hip and lumbar spine were evaluated by dual energy X-ray absorptiometry (DEXA), and body composition (LBM and BFM) by whole body DEXA. RESULTS: Oral TU significantly increased BMD at Month 12 at the lumbar spine (240 mg/d), total hip (240 mg/d), and trochanter and intertrochanter (160 and 240 mg/d) compared with placebo. Oral TU significantly increased LBM at Months 6 and 12 for all oral TU groups compared with placebo. BFM significantly decreased at Month 6 (all oral TU groups) and Month 12 (160 mg/d) compared with placebo. The effects on BMD and body composition showed a clear dose response. CONCLUSIONS: Treatment with oral TU led to improvement in BMD, LBM and BFM in aging men with symptomatic TD.

A Comparison of the Blood Glucose, Growth Hormone, and Cortisol Responses to Two Doses of Insulin (0.15 U/kg vs. 0.10 U/kg) in the Insulin Tolerance Test: A Single-Centre Audit of 174 Cases.

Objective: The insulin tolerance test (ITT) is the gold standard endocrine test used to assess the integrity of the growth hormone (GH) and cortisol axes. The ITT has potential risks, and severe hypoglycaemia may necessitate intravenous glucose rescue. There is no clear consensus as to the optimal insulin dose for the ITT. Therefore, we sought to compare the standard dose (0.15 U/kg) and a low-dose ITT (0.1 U/kg). Design: Single-centre audit of ITT data (2012-2021). Patients and Measurements. Patients who underwent an ITT to assess possible GH deficiency/adrenal insufficiency were included. Glucose, GH, and cortisol were measured at baseline and 30, 45, 60, 90, and 120 minutes following I.V. insulin bolus (0.15 U/kg or 0.10 U/kg). Results: Of the ITTs performed, only 3/177 (1.7%) did not achieve adequate hypoglycaemia (≤2.2 mmol/L) with a single insulin dose. In total, 174 patients (43.5 ± 12.1 yrs, mean ± standard deviation) were included for analysis (0.15 U/kg: n = 113, 0.10 U/kg: n = 61). All 174 subjects had adequate hypoglycaemia regardless of baseline fasting blood glucose level or insulin dose. Neither nadir glucose nor glucose delta (i.e., baseline minus nadir) differed between insulin doses. Trends in both cortisol and GH responses over time were similar between groups, and a greater proportion of patients receiving the standard dose had an adequate cortisol response (77/106 (72.6%) vs. 32/60 (53.3%), p=0.01). The rates of glucose rescue did not differ in a subset of 79 patients, with on-demand glucose rescue in 4/35 (11%) for the standard dose and 2/44 (5%) for the low dose (p=0.25). Conclusions: Our results suggest that the low-dose ITT produces comparable glucose, cortisol, and GH responses to the higher dose. Given the risks associated with hypoglycaemia, the low dose appears to be preferable to the standard dose ITT in most circumstances.

Male hormonal contraception: a double-blind, placebo-controlled study.

BACKGROUND: This study was performed to assess spermatogenesis suppression and safety of a new combination of an etonogestrel (ENG) implant combined with testosterone undecanoate (TU) injections for male contraception. This is the first large placebo-controlled study for male hormonal contraception. DESIGN AND STUDY SUBJECTS: In this double-blind, multicenter study, we randomly assigned 354 healthy men to receive either a low- or high-release ENG implant sc combined with im TU injections (750 mg every 10 or 12 wk or 1000 mg every 12 wk) or placebo implant and injections. Treatment duration was 42 or 44 wk and posttreatment follow-up at least 24 wk. RESULTS: Overall, spermatogenesis was suppressed to 1 million/ml or less at wk 16 in 89% of men, with approximately 94% in two high-release ENG groups. Suppression was maintained up to the end of the treatment period in 91% of men. For all men who completed the treatment period, 3% never achieved 1 million/ml or less. Median recovery time to a sperm concentration above 20 million/ml was 15 wk (mean 17 wk, 95% confidence interval 16-18 wk). Treatment was well tolerated. As compared with the placebo group, more men in the active treatment groups reported adverse events such as weight gain, mood changes, acne, sweating, or libido change. For both spermatogenesis suppression and safety, differences were small between the active treatment groups. CONCLUSIONS: The combination of an ENG implant with TU injections is a well-tolerated male hormonal method, providing effective and reversible suppression of spermatogenesis. Although the results are good, there is still room for improvement, possibly by adjusting the dose regimen or changing the mode of application.

Extended and flexible domain solution structure of the extracellular matrix protein anosmin-1 by X-ray scattering, analytical ultracentrifugation and constrained modelling.

Kallmann's syndrome corresponds to a loss of sense of smell and hypogonadotrophic hypogonadism. Defects in anosmin-1 result in the X-linked inherited form of Kallmann's syndrome. Anosmin-1 is an extracellular matrix protein comprised of an N-terminal, cysteine-rich (Cys-box) domain and a whey acidic protein-like (WAP) domain, followed by four fibronectin type III (FnIII) domains. The solution structures of recombinant proteins containing the first three domains (PIWF1) and all six domains (PIWF4) were determined by X-ray scattering and analytical ultracentrifugation. Guinier analyses showed that PIWF1 and PIWF4 have different radii of gyration (R(G)) values of 3.1 nm and 6.7 nm, respectively, but similar cross-sectional radii of gyration (R(XS)) values of 1.5 nm and 1.9 nm, respectively. Distance distribution functions showed that the maximum lengths of PIWF1 and PIWF4 were 11 nm and 23 nm, respectively. Analytical ultracentrifugation gave sedimentation coefficients of 2.52 S and 3.55 S for PIWF1 and PIWF4, respectively. The interpretation of the scattering data by constrained modelling requires homology models for all six domains in anosmin-1. While models were already available for the WAP and FnIII domains, searches suggested the Cys-box domain may resemble the cysteine-rich region of the insulin-like growth factor receptor. Automated constrained molecular modelling based on joining the anosmin-1 domains with structurally randomised linkers resulted in 10,000 models for anosmin-1. A trial-and-error search showed that about 0.1-1.4% of these models fitted the X-ray data. The best models showed that the three domains and six domains in PIWF1 and PIWF4, respectively, were extended. The inter-domain linkers in anosmin-1 could not all be extended at the same time, and there was evidence for inter-domain flexibility. Models with folded-back domain arrangements do not fit the data. These solution structures account for the known biological function of anosmin-1, in particular its ability to interact with its three macromolecular ligands.

GnRH neuronal development: insights into hypogonadotrophic hypogonadism.

Pulsatile secretion of the hypothalamic decapeptide gonadotrophin-releasing hormone (GnRH) regulates activity of the pituitary-gonadal reproductive axis. Defects of this neuroendocrine axis necessarily result in hypogonadotrophic hypogonadism. In many vertebrate species studied, the main population of GnRH neurones originates extracranially within the olfactory system. In humans, both olfactory and GnRH systems are affected in Kallmann's syndrome--resulting in isolated hypogonadotrophic hypogonadism (IHH) combined with anosmia (loss of sense of smell). Familial IHH is also caused by other genetic conditions, which prevent GnRH from activating luteinizing hormone/follicle-stimulating hormone release from pituitary gonadotrophs. However, many cases of IHH have no defined chromosomal abnormality and, in the absence of pedigree analysis, studying the biological mechanisms controlling migration of GnRH neurones through the olfactory system into the developing central nervous system might reveal additional genetic pathways that play a role in the pathogenesis of IHH.

A comparison of a novel testosterone bioadhesive buccal system, striant, with a testosterone adhesive patch in hypogonadal males.

A novel delivery system has been developed for testosterone replacement. This formulation, COL-1621 (Striant), a testosterone-containing buccal mucoadhesive system, has been shown in preliminary studies to replace testosterone at physiological levels when used twice daily. Therefore, the current study compared the steady-state pharmacokinetics and tolerability of the buccal system with a testosterone-containing skin patch (Andropatch or Androderm) in an international multicenter study of a group of hypogonadal men. Sixty-six patients were randomized into two groups; one applied the buccal system twice daily, whereas the other applied the transdermal patch daily, in each case for 7 d. Serum total testosterone and dihydrotestosterone concentrations were measured at d 1, 3 or 4, and 6, and serially over the last 24 h of the study. Pharmacokinetic parameters for each formulation were calculated, and the two groups were compared. The tolerability of both formulations was also evaluated. Thirty-three patients were treated with the buccal preparation, and 34 were treated with the transdermal patch. The average serum testosterone concentration over 24 h showed a mean of 18.74 nmol/liter (SD =; 5.90) in the buccal system group and 12.15 nmol/liter (SD =; 5.55) in the transdermal patch group (P < 0.01). Of the patients treated with the buccal system, 97% had average steady-state testosterone concentrations within the physiological range (10.41-36.44 nmol/liter), whereas only 56% of the transdermal patch patients achieved physiological total testosterone concentrations (P < 0.001 between groups). Testosterone concentrations were within the physiological range in the buccal system group for a significantly greater portion of the 24-h treatment period than in the transdermal patch group (mean, 84.9% vs. 54.9%; P < 0.001). Testosterone/dihydrotestosterone ratios were physiological and similar in both groups. Few patients experienced major adverse effects from either treatment. No significant local tolerability problems were noted with the buccal system, other than a single patient withdrawal. We conclude that this buccal system is superior to the transdermal patch in achieving testosterone concentrations within the normal range. It may, therefore, be a valuable addition to the range of choices for testosterone replacement therapy.

Hypogonadotropic hypogonadism.

Hypogonadotropic hypogonadism is characterized by failure of gonadal function secondary to deficient gonadotropin secretion, resulting from either a pituitary or hypothalamic defect, and is commonly seen in association with structural lesions or functional defects affecting this region. Although the genetic basis for idiopathic hypogonadotropic hypogonadism is largely unknown, mutations in several genes involved in the hypothalamo-pituitary-gonadal axis development and function have recently been implicated in the pathogenesis of this condition. Genes currently recognized to be involved include KAL-1 (associated with X-linked Kallmann Syndrome), gonadotropin-releasing hormone (GnRH) receptor, gonadotropins, pituitary transcription factors (HESX1, LHX3, and PROP-1), orphan nuclear receptors (DAX-1, associated with X-linked adrenal hypoplasia congenital, and SF-1), and three genes also associated with obesity (leptin, leptin receptor, and prohormone convertase 1 [ PC1]). Study of these mutations provides an important contribution in the understanding of the different stages of the reproductive axis development and physiology. Treatment options currently available for puberty induction, maintenance replacement therapy, and fertility induction are considered here. Gametogenesis can be induced with either exogenous gonadotropin or pulsatile GnRH therapy, depending on the etiology.

SOX2 regulates the hypothalamic-pituitary axis at multiple levels.

Sex-determining region Y (SRY) box 2 (SOX2) haploinsufficiency causes a form of hypopituitarism in humans that is characterized by gonadotrophin deficiency known as hypogonadotrophic hypogonadism. Here, we conditionally deleted Sox2 in mice to investigate the pathogenesis of hypogonadotrophic hypogonadism. First, we found that absence of SOX2 in the developing Rathke pouch of conditional embryos led to severe anterior lobe hypoplasia with drastically reduced expression of the pituitary-specific transcription factor POU class 1 homeobox 1 (POU1F1) as well as severe disruption of somatotroph and thyrotroph differentiation. In contrast, corticotrophs, rostral-tip POU1F1-independent thyrotrophs, and, interestingly, lactotrophs and gonadotrophs were less affected. Second, we identified a requirement for SOX2 in normal proliferation of periluminal progenitors; in its absence, insufficient precursors were available to produce all cell lineages of the anterior pituitary. Differentiated cells derived from precursors exiting cell cycle at early stages, including corticotrophs, rostral-tip thyrotrophs, and gonadotrophs, were generated, while hormone-producing cells originating from late-born precursors, such as somatotrophs and POU1F1-dependent thyrotrophs, were severely reduced. Finally, we found that 2 previously characterized patients with SOX2 haploinsufficiency and associated hypogonadotrophic hypogonadism had a measurable response to gonadotropin-releasing hormone (GnRH) stimulation, suggesting that it is not the absence of gonadotroph differentiation, but rather the deficient hypothalamic stimulation of gonadotrophs, that underlies typical hypogonadotrophic hypogonadism.

Oral testosterone replacement in symptomatic late-onset hypogonadism: effects on rating scales and general safety in a randomized, placebo-controlled study.

OBJECTIVE: To investigate the effects of oral testosterone undecanoate (TU) on symptoms associated with late-onset hypogonadism (LOH). Design Multicenter, randomized, double-blind, placebo-controlled. METHODS: The study was performed in 14 study centers in seven European countries. Men > or =50 years (n=322) with symptoms of hypogonadism and testosterone deficiency (calculated free testosterone <0.26 nmol/l) were randomized and treated for 12 months with placebo or oral TU 80, 160 or 240 mg/day. Primary outcome was the total score on the Aging Males' Symptoms (AMS) rating scale after six months of treatment. RESULTS: Treatment of mild-to-moderate LOH symptoms in subjects with borderline hypogonadism with oral TU resulted in an improved total AMS score at month 6, but differences between groups were not statistically significant. There was greater improvement in subjects <60 years when compared with subjects > or =60 years (P=0.001), but baseline testosterone level had no influence on treatment response. The AMS sexual symptoms domain improved with oral TU 160 mg/day at months 6 (P=0.008) and 12 (P=0.012) compared with placebo, but not with 80 and 240 mg/day. Treatment was well-tolerated and there were no between-group differences in adverse events or drop-out rates. CONCLUSIONS: In one of the largest placebo-controlled studies of testosterone therapy in LOH, oral TU did not improve total AMS score in subjects with mild-to-moderate symptoms compared with placebo, except the sexual symptom sub-domain where a modest improvement was reported with oral TU 160 mg/day.

Serum IGF-I levels and IGF-I gene splicing in muscle of healthy young males receiving rhGH.

OBJECTIVE: Elevated growth hormone (GH) levels lead to increased circulating insulin-like growth factor-I (IGF-I), but the effects on localised muscle IGF-I splice variant expression is not known. The effects of rhGH administration, with or without an acute bout of high resistance exercise, were measured on serum IGF-I and on the mRNA levels of IGF-I splice variants in the vastus lateralis muscle of healthy young men. DESIGN: The study was a randomised double blind trial with a crossover design. Seven subjects were randomly assigned to a group receiving daily injections of rhGH (0.075IU kg(-1)day(-1)) or placebo for a two week period. Following a one month washout, the groups were reversed. RESULTS: Administration of rhGH increased circulating IGF-I from 31.8+/-3.2 to 109+/-5.4 nmol/L (p<0.05). There was no effect of the exercise bout. RNA was extracted from muscle biopsies obtained from exercised and non-exercised legs 2.5h after the cessation of the exercise. Transcript expression was measured using Real-time QPCR. There was no effect of either exercise or rhGH administration on IGF-I 5' (Class 1 or Class 2) or 3' (IGF-IEa, or MGF) transcripts. CONCLUSION: Although rhGH administration has an effect on liver IGF-I expression, as shown by increase in circulating IGF-I, muscle IGF-I expression is unaffected in young healthy subjects with normal GH profile. The findings contrast with those of a previous study in which GH deficient elderly men showed higher muscle IGF-I 3' splice variant levels following rhGH administration with and without resistance training. Unlike in the liver, muscle Class1 and 2 IGF-I expression do not change significantly following administration of rhGH.

Mutations within the transcription factor PROP1 are rare in a cohort of patients with sporadic combined pituitary hormone deficiency (CPHD).

OBJECTIVE: Mutations within the pituitary-specific paired-like homeobox gene PROP1 have been described in 50-100% of patients with familial combined pituitary hormone deficiency (CPHD). We screened a cohort of sporadic (n = 189) and familial (n = 44) patients with hypopituitarism (153 CPHD and 80 isolated hormone deficiencies) for mutations within the coding sequence of PROP1. DESIGN AND PATIENTS: Patients with congenital hypopituitarism were recruited from the London Centre for Paediatric Endocrinology as well as several national and international centres. The pituitary phenotype ranged from isolated growth hormone deficiency (IGHD) to panhypopituitarism. Clinical data, including endocrine and neuro-radiological studies were obtained from patient records, and DNA was collected and screened for mutations within PROP1 using PCR and single-stranded conformation polymorphism (SSCP) analysis. Positive results on SSCP were sequenced directly. RESULTS: The prevalence of PROP1 mutations in unselected sporadic cases of hypopituitarism was lower (1.1%) than in familial cases (29.5%). PROP1 mutations can be associated with a highly variable phenotype, and both pituitary hypoplasia and pituitary hyperplasia. We describe the waxing and waning of a pituitary mass over 20 months in association with a PROP1 mutation that is predicted to lead to complete loss of function. Additionally, we have identified a possible founder mutation in CPHD patients from the Indian subcontinent. CONCLUSIONS: PROP1 mutations are rare in sporadic cases of CPHD, although the prevalence rises if there is a positive family history or if the patients are carefully selected with respect to the endocrine and neuroradiological phenotype. There is considerable phenotypic variability in families with the same mutation, indicating the role of other genetic or environmental factors on phenotypic expression. Finally, the pituitary enlargement that is observed in patients with PROP1 mutations can wax and wane in size before eventual involution.

Ghrelin can bind to a species of high density lipoprotein associated with paraoxonase.

Ghrelin is a 28-residue peptide hormone that is principally released from the stomach during fasting and prior to eating. Two forms are present in human plasma: the unmodified peptide and a less abundant acylated version, in which octanoic acid is attached to the third residue, a serine, via an ester linkage. The acylated form of ghrelin acts as a ligand for the growth hormone secretagogue receptor and can stimulate the release of growth hormone from the pituitary gland. It also initiates behavioral and metabolic adaptations to fasting. Here we show that an immobilized form of ghrelin specifically binds a species of high density lipoprotein associated with the plasma esterase, paraoxonase, and clusterin. Both free ghrelin and paraoxon, a substrate for paraoxonase, can inhibit this interaction. An endogenous species of ghrelin is found to co-purify with high density lipoprotein during density gradient centrifugation and subsequent gel filtration. This interaction links the orexigenic peptide hormone ghrelin to lipid transport and metabolism. Furthermore, the interaction of the esterified hormone ghrelin with a species of HDL containing an esterase suggests a possible mechanism for the conversion of ghrelin to des-acyl ghrelin.