Graded inhibition of pulsatile luteinizing hormone secretion by a selective gonadotropin-releasing hormone (GnRH)-receptor antagonist in healthy men: evidence that age attenuates hypothalamic GnRH outflow

Association of cannabis abuse/dependence on risks of erectile dysfunction and testosterone deficiency using a large claims database analysis

BACKGROUND

Cannabis is widely consumed across the United States; however, studies assessing the association between cannabis use and male sexual health, specifically erectile dysfunction (ED) and testosterone deficiency (TD), have mixed results and small sample sizes.

AIM

To evaluate the impact of cannabis abuse/dependence on risks of ED, phosphodiesterase-5 inhibitor (PDE5-i) prescription, TD, and testosterone replacement therapy (TRT) using a population-level analysis.

METHODS

We sampled men ≥18 years old from the large claims database, TriNetX, in 2025. Patients previously diagnosed with or treated for ED or TD and those with prior prostatectomy were excluded. Patients were split into two cohorts: diagnoses of cannabis abuse/dependence or not. Cohorts were propensity score-matched on 49 pertinent factors. Risk of ED, TD, PDE5-i prescription, and TRT were compared at 3 months-1 year (patients from 2005-2024) and 3-5 years (patients from 2005-2020) from cannabis diagnoses. Subgroups of age younger or older than 40 years were also analyzed. Kaplan-Meier survival analysis was performed to assess differences in time to development of ED and TD.

OUTCOMES

Primary outcomes were risk of diagnosis of ED or TD (testosterone level <300 ng/dL). Secondary outcomes were risk of new prescription of PDE5-i or TRT.

RESULTS

Between 2005-2024, 30 964 patients with and 1 473 182 without cannabis diagnoses were identified with 29 442 in each cohort after matching. Between 2005-2020, 17 948 patients with and 839 496 without cannabis abuse/dependence were identified, with 17 211 in each cohort after matching. Cannabis abuse/dependence was significantly associated with ED (0.9% vs. 0.2%, RR = 3.99 [3.05, 5.21]), TD (0.2% vs. 0.1%, RR = 2.19 [1.45, 3.31]), and PDE5-i prescription (0.8% vs. 0.2%, RR = 3.80 [2.86, 5.04]) at 3 months-1 year, and only ED at 3-5 years (1.61% vs. 1.34%, RR = 1.20, 95% CI = [1.01, 1.43]). Kaplan-Meier analysis revealed significantly shorter time to development of ED (HR = 1.65, 95% CI = [1.47, 1.85]) and TD (HR = 1.34, 95% CI = 1.07, 1.69]) associated with cannabis abuse/dependence. No association between cannabis abuse/dependence and TRT was found. In those <40 years old, only ED and PDE5-i were significant at 3 months-1 year, but not at 3-5 years.

CLINICAL IMPLICATIONS

Our findings support an association between cannabis abuse/dependence, ED, and TD, which providers may consider when treating patients with these diagnoses.

STRENGTHS AND LIMITATIONS

Strengths include having a large, national sample of patients. Limitations include inability to assess dose-dependent relationships and using diagnosis codes as proxies for cannabis use.

CONCLUSION

Cannabis abuse/dependence is associated with increased risk of ED, PDE5-i prescription, and TD.

GnRH and Cognition

GnRH is traditionally recognized as the central regulator of reproduction through its pulsatile secretion, which governs the hypothalamic-pituitary-gonadal axis. However, recent evidence has highlighted its broader role in brain development and function, including in cognitive and higher intellectual processes. GnRH production follows distinct phases, from its early activation during minipuberty-the first postnatal activation of GnRH neurons during the infantile period-, its reactivation and stabilization starting at puberty, and its eventual decline with age and the loss of gonadal steroid feedback. This evolution depends on the establishment, maturation and activation of GnRH neurons, a complex process regulated by the cellular and molecular environment of these neurons, including multiple neuronal and glial types as well as a minipubertal "switch" in gene expression, the perturbation of which may have long-term or delayed consequences for both reproductive and cognitive function. The cognitive role of GnRH may be related to its recently revealed involvement in maintaining myelination and synaptic plasticity, whereas disruptions in its finely tuned rhythmic secretion, either age-related or pathological, are associated with cognitive decline and neurodegenerative disorders. Restoring physiological GnRH levels and pulsatility can reverse age-related cognitive decline and improve sensory functions even in adulthood, suggesting a mobilization of the "cognitive reserve" in both animal models and human patients. This review highlights recent advances in our understanding of the GnRH system and the therapeutic potential of pulsatile GnRH therapy to mitigate age-related cognitive decline and neurodegenerative processes.

MicroRNA profiling reveals the role of miR-133b-3p in promoting apoptosis and inhibiting cell proliferation and testosterone synthesis in mouse TM3 cells

Late-onset hypogonadism (LOH) is an age-related clinical and biological syndrome in which serum testosterone deficiency is an important characteristic and diagnostic indicator. In this study, we firstly analyzed the difference in the expression level of three miR-133 s (including miR-133a-3p, miR-133a-5p, and miR-133b-3p) in rat testis samples, blood samples from mice before and 1 wk after testis removal, and mouse TM3 cells. Secondly, the mimics and inhibitors corresponding to the three miR-133 s of mouse were transfected into TM3 cells separately to determine the correlation between the three miRNAs. Finally, using mouse TM3 cells to analyze the effect of miR-133b overexpression or inhibition on the proliferation and apoptosis of mouse testicular Leydig cells, the effect on genes related to testosterone synthesis, and the effect on the level of testosterone in the culture medium. We found that, compared with the testis tissue of newborn rats, miR-133a-5p was increased in adult rats, and miR-133a-3p and miR-133b-3p were decreased. In addition, 1 wk after the testis was removed, the expression levels of these three miRNAs in the blood of adult mice decreased. The correlation of the three miRNAs was summarized, and it was found that miR-133b-3p played an important role in it. In TM3 cells, overexpression of miR-133b-3p suppressed the proliferation and promotes apoptosis of cells, suppressed the expression level of most genes related to cell proliferation and testosterone synthesis, and the concentration of testosterone in the culture medium decreased while these phenomena can be reversed by the inhibition of miR-133b-3p expression. It was found that miR-133b-3p can regulate testosterone production in TM3 cells at least by targeting FSCN1. The above results suggest that miR-133b-3p plays an important role in regulating testosterone synthesis. These findings also provide new candidate diagnostic indicators for late-onset hypogonadism in men and provide new clues for the further study of pathogenesis.

Mobility and Biomechanical Functions in the Aging Male: Testosterone and the Locomotive Syndrome

In the current aging society, the occurrence of the locomotive syndrome, a condition in which the locomotive organs are impaired, is increasing. The locomotive system includes support (bones), mobility and impact absorption (joints and intervertebral disks), drive and control (muscles, nerves), and network (blood vessels). The impairment of any of those systems can lead to a major decrease in quality of life. In recent years, several studies on methods to improve and prevent conditions impairing the locomotive syndrome have been conducted. Almost in parallel with the structure supporting mobility and body functions, testosterone levels decrease with age. Testosterone is a hormone-regulating several pathways affecting each aspect of the locomotive syndrome. Testosterone is regulated by the pituitary gland triggering several processes in the body through genomic and non-genomic pathways, affecting muscles, bones, nerves, joints, intervertebral discs, and blood vessels. The purpose of this review is to investigate the role of testosterone in each of the systems involved in the locomotive syndrome.

Impaired prolactin transport into the brain and functional responses to prolactin in aged male mice

Ageing is related to changes in a number of endocrine systems that impact on the central actions of hormones. The anterior pituitary hormone prolactin is present in the circulation in both males and females, with widespread expression of the prolactin receptor throughout the forebrain. We aimed to investigate prolactin transport into the brain, as well as circulating levels of prolactin and functional responses to prolactin, in aged male mice (23 months). Transport of ¹²⁵ I-labelled prolactin (¹²⁵ I-prolactin) from the peripheral circulation into the brain was suppressed in aged compared to young adult (4 months) male mice, with no significant transport into the brain occurring in aged males. We subsequently investigated changes in the negative-feedback regulation of prolactin secretion and prolactin-induced suppression of luteinising hormone (LH) pulsatile secretion in aged male mice. Feedback regulation of prolactin secretion appeared to be unaffected in aged males, with no change in levels of circulating prolactin, and normal prolactin-induced phosphorylated signal transducer and activator of transcription 5(pSTAT5) immunoreactivity in tuberoinfundibular dopaminergic (TIDA) neurones in the arcuate nucleus. There were, however, significant impairments in the ability of prolactin to suppress LH pulsatile secretion in aged males. In young adult males, acute prolactin administration significantly decreased LH pulses from 1.5 ± 0.19 pulses of LH in 4 hours to 0.5 ± 0.27 pulses. In contrast, prolactin did not suppress LH pulse frequency in aged males, with prolactin leading to an increase in mean LH concentration. These data demonstrate the emergence of impairments in prolactin transport into the brain and deficits in specific functional responses to prolactin with ageing.

Hypothalamic Response to Kisspeptin-54 and Pituitary Response to Gonadotropin-Releasing Hormone Are Preserved in Healthy Older Men

BACKGROUND

Male testosterone levels decline by 1% per year from the age of 40 years. Whilst a primary testicular deficit occurs, hypothalamic or pituitary dysregulation may also coexist. This study aimed to compare the hypothalamic response to kisspeptin-54 and the pituitary response to gonadotropin-releasing hormone (GnRH) of older men with those of young men.

METHODS

Following 1 h of baseline sampling, healthy older men (n = 5, mean age 59.3 ± 2.9 years) received a 3-h intravenous infusion of either vehicle, kisspeptin-54 0.1, 0.3, or 1.0 nmol/kg/h or GnRH 0.1 nmol/kg/h, on five different study days. Serum gonadotropins and total testosterone were measured every 10 min and compared to those of young men (n = 5/group) (mean age 28.9 ± 2.0 years) with a similar body mass index (24 kg/m2) who underwent the same protocol.

RESULTS

Kisspeptin-54 and GnRH significantly stimulated serum gonadotropin release in older men compared to vehicle (p < 0.001 for all groups). Gonadotropin response to kisspeptin-54 was at least preserved in older men when compared to young men. At the highest dose of kisspeptin-54 (1.0 nmol/kg/h), a significantly greater luteinising hormone (LH) (p = 0.003) response was observed in older men. The follicle-stimulating hormone (FSH) response to GnRH was increased in older men (p = 0.002), but the LH response was similar (p = 0.38). Serum testosterone rises following all doses of kisspeptin-54 (p ≤ 0.009) were reduced in older men.

CONCLUSIONS

Our data suggest that healthy older men without late-onset hypo-gonadism (LOH) have preserved hypothalamic response to kisspeptin-54 and pituitary response to GnRH, but impaired testicular response. Further work is required to investigate the use of kisspeptin-54 to identify hypothalamic deficits in men with LOH.

Adult-Onset Hypogonadism

In August 2015, an expert colloquium commissioned by the Sexual Medicine Society of North America (SMSNA) convened in Washington, DC, to discuss the common clinical scenario of men who present with low testosterone (T) and associated signs and symptoms accompanied by low or normal gonadotropin levels. This syndrome is not classical primary (testicular failure) or secondary (pituitary or hypothalamic failure) hypogonadism because it may have elements of both presentations. The panel designated this syndrome adult-onset hypogonadism (AOH) because it occurs commonly in middle-age and older men. The SMSNA is a not-for-profit society established in 1994 to promote, encourage, and support the highest standards of practice, research, education, and ethics in the study of human sexual function and dysfunction. The panel consisted of 17 experts in men's health, sexual medicine, urology, endocrinology, and methodology. Participants declared potential conflicts of interest and were SMSNA members and nonmembers. The panel deliberated regarding a diagnostic process to document signs and symptoms of AOH, the rationale for T therapy, and a monitoring protocol for T-treated patients. The evaluation and management of hypogonadal syndromes have been addressed in recent publications (ie, the Endocrine Society, the American Urological Association, and the International Society for Sexual Medicine). The primary purpose of this document was to support health care professionals in the development of a deeper understanding of AOH, particularly in how it differs from classical primary and secondary hypogonadism, and to provide a conceptual framework to guide its diagnosis, treatment, and follow-up.

Age-related testosterone decline is due to waning of both testicular and hypothalamic-pituitary function

Hypogonadism is a condition in which the endogenous secretion of testosterone is either insufficient or inadequate to maintain serum testosterone levels within normal range, and may manifest as a variety of signs and symptoms. Age-related hypogonadism is due to a combination of primary hypogonadism (testicular failure) and secondary hypogonadism (hypothalamic-pituitary axis failure). This review provides insight into the mechanisms resulting in the multifactorial nature of acquired androgen-deficiency, and outlines the current controversy regarding testosterone-replacement therapy in aging males.

Analysis of the impact of intravenous LH pulses versus continuous LH infusion on testosterone secretion during GnRH-receptor blockade

Gonadotrophin-releasing hormone (GnRH) pulsatility is required for optimal luteinizing hormone (LH) secretion, but whether LH pulsatility is required for physiological testosterone (T) secretion is not known. To test the postulate that pulses of recombinant human (rh) LH stimulate greater T secretion than continuous infusion of the same dose, a potent selective GnRH antagonist was administered overnight to 19 healthy men ages 18-49 yr. Subjects then received saline or rhLH intravenously continuously or as 6-min pulses intravenously every 1 or 2 h at the same total dose. Blood was sampled every 10 min for 10 h to quantify T responses. For the four interventions, the descending rank order of mean LH and mean T concentrations was 1-h = 2-h rhLH pulses > continuous rhLH > saline (P < 10(-3)). Plateau LH and T concentrations correlated positively (R(2) = 0.943, P = 0.029) as did LH concentrations and LH half-lives (R(2) = 0.962, P = 0.019). Percentage pulsatile T secretion assessed by deconvolution analysis (Keenan DM, Takahashi PY, Liu PY, Roebuck PD, Nehra AX, Iranmanesh A, Veldhuis JD. Endocrinology 147: 2817-2828, 2006) was the highest (P = 0.019), and half-time to attain peak T concentrations was the shortest (P < 10(-6)), for 1-h rhLH pulses. Approximate entropy (a pattern-regularity measure) revealed more orderly T secretion for 1- than 2-h rhLH pulses (P = 0.0076). Accordingly, a pulsatile LH signal, while not obligatory to maintain mean T concentrations, controls the mean plasma LH concentration and determines quantifiable patterns of T secretion. These data introduce the question whether blood T patterns in turn supervise distinctive target-tissue responses.

Older men exhibit reduced efficacy of and heightened potency downregulation by intravenous pulses of recombinant human LH: a study in 92 healthy men

Direct sampling of the human spermatic veins has disclosed concomitant LH and testosterone (T) pulses, suggesting pulsatile LH concentration-dependent stimulation of T secretion. However, studies to date have examined this hypothesis using only pharmacological stimulation with hCG. The present study tests the hypothesis that age is marked by decreased T secretory responses to repeated near-physiological iv pulses of recombinant human LH administered in a Clinical Translational Science Center. Participants included 92 healthy men aged 18-75 yr with BMI 18-34 kg/m(2). The contribution of endogenous LH pulses was minimized by combined injection of a selective GnRH receptor antagonist sc and successive pulses of biosynthetic LH iv. A new analytical dose response model was applied to estimate the properties of exogenous LH's drive of T secretion. Regression of LH-T dose response potency estimates on age showed that the efficacy of pulses of biosynthetic LH progressively decreased with age (P = 0.014, r = 0.26). Testis sensitivity to exogenous LH pulses also declined with age (P = 0.011, r = 0.27). Moreover, estimated Leydig cell downregulation by LH pulses rose significantly with age (P = 0.039, r = 0.22). These outcomes were selective, since the recovery potency of infused LH was not affected by age but was reduced by increasing BMI (P = 0.011, r = 0.27). Assuming stable bioactivity of infused recombinant human LH, these novel data indicate that factors associated with age and BMI attenuate LH efficacy and testis sensitivity and augment Leydig cell downregulation in healthy men.

Noninvasive analytical estimation of endogenous GnRH drive: analysis using graded competitive GnRH-receptor antagonism and a calibrating pulse of exogenous GnRH

Homeostatic control of endocrine systems proceeds via feedforward (agonistic, stimulatory) and feedback (antagonistic, inhibitory) interactions mediated via implicit dose-response functions. However, neither the feedback/feedforward pathways nor the dose-response interfaces are directly observed in vivo. Thus, the goal was to formulate and estimate an ensemble construct of time-varying feedback/feedforward interactions among GnRH, LH, and testosterone (T) in the male gonadal axis. The new analytical model revises and extends an earlier construct by: 1) allowing systemic T concentrations to inhibit hypothalamic GnRH output; 2) estimating GnRH outflow after injection of a calibrating pulse of biosynthetic GnRH; 3) framing the pituitary response to GnRH as a secretory burst, rather than continuous LH release; and 4) regressing feedback and feedforward ensemble parameters on age, rather than evaluating age dichotomously. Application of this methodology in 21 men aged 23-72 yr unveiled age-related 1) diminution of GnRH efficacy normalized for the decline in free T with age (P = 0.016), 2) potentiation of maximal T feedback onto (inhibition of) GnRH secretion (P = 0.006), and 3) accentuation of hypothalamic GnRH's sensitivity to T repression (P = 0.003). Outcomes were specific, because injected GnRH agonist and antagonist concentrations were invariant of age. We conclude that combining experimental and analytical strategies may provide a noninvasive means to investigate and decipher feedback determinants of unobserved endocrine signal(s).

Age-dependent regression analysis of male gonadal axis

The mechanisms by which aging progressively depletes testosterone (Te) availability in the male are unknown. Accordingly, the objective was to estimate brain gonadotropin-releasing hormone (GnRH) outflow (release and action), which cannot be observed directly, on the basis of downstream effects on pituitary luteinizing hormone (LH) secretion. LH, in turn, feeds forward on (stimulates) gonadal Te secretion, which then feeds back on (inhibits) GnRH-driven LH secretion. LH and Te concentrations were measured repetitively (every 10 min) over 18 h during graded pharmacological blockade of endogenous GnRH outflow in 24 healthy 20- to 72-yr-old men. Data were analyzed using a new age-dependent regression model of GnRH-LH-Te interactions to estimate pulsatile LH secretion and elimination, GnRH outflow, LH feedforward, and Te feedback. By incorporating regression on age within the dose-response model, we show that aging erodes all three primary forward and reverse pathways linking the brain, pituitary gland, and testes. Aging is associated with concomitant deficits in GnRH --> LH feedforward, LH --> Te feedforward, and Te --> GnRH/LH feedback. The analytical formalism should be generalizable to other ensemble regulatory systems, such as those that control growth, reproduction, stress adaptations, and glucose metabolism.

Aging in healthy men impairs recombinant human luteinizing hormone (LH)-stimulated testosterone secretion monitored under a two-day intravenous pulsatile LH clamp

CONTEXT

Testosterone (Te) depletion in aging men in principle could reflect deficits in the hypothalamus, pituitary gland, or testis. Available pharmacological studies of possible failure of Leydig cell steroidogenesis remain inconclusive.

OBJECTIVE

The objective of the study was to assess Te secretion in older and young men in response to near physiological LH stimulation.

INTERVENTION

Pulsatile i.v. infusion of recombinant human LH was administered for 2 d to stimulate Te secretion during suppression of endogenous LH concentrations with a potent selective GnRH receptor antagonist (ganirelix). SUBJECTS/CONTEXT: Healthy older (aged 60-73 yr, n = 8) and young (19-30 yr, n = 13) men were studied in an academic setting.

MEASURES

Pulsatile LH and Te concentrations on the second day of exogenous LH stimulation were measured.

RESULTS

Serum ganirelix concentrations and infused LH pulse increments were similar by age. In contrast, older subjects manifested: 1) reduced mean Te concentrations (P = 0.016), Te peak heights (P = 0.014), increments (P = 0.010), summed areas (P < 0.013), and interpeak Te concentrations (P = 0.023); 2) decreased Te to LH concentration ratios (P = 0.002); 3) diminished LH-Te feed-forward synchrony (P = 0.020); and 4) a blunted amplitude (P = 0.036) and advanced phase (P = 0.013) of diurnal Te rhythms.

CONCLUSION

A novel regimen of pulsatile LH stimulation for 48 h during GnRH receptor blockade unmasks deficits in pulsatile, basal, synchronous, and nyctohemeral Te secretion in healthy older men. These findings do not exclude concomitant defects in GnRH outflow and/or Te-negative feedback in the aging male.