Cortical vasopressin and oxytocin neurons represent a critical neuropeptidergic system that modulates cognitive function, social behavior, and stress responses throughout the brain. While the cell bodies of vasopressin and oxytocin neurons are primarily located in the hypothalamic paraventricular nucleus (PVN) and supraoptic nucleus (SON), these neurons project extensively to cortical and limbic regions, where they release their neuropeptides as volume transmission or synaptic signals to influence synaptic plasticity, memory consolidation, and social cognition [1](https://pubmed.ncbi.nlm.nih.gov/32898456/). In neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD), the vasopressin and oxytocin systems undergo significant alterations that contribute to the characteristic behavioral and cognitive symptoms observed in these disorders [4](https://pubmed.ncbi.nlm.nih.gov/9096745/). The dysfunction of these neuropeptidergic systems has emerged as a potential therapeutic target, with ongoing research exploring oxytocin and vasopressin-based interventions for treating social memory deficits, agitation, and other neuropsychiatric symptoms in dementia patients [8](https://pubmed.ncbi.nlm.nih.gov/31077897/).
Cortical vasopressin and oxytocin neurons represent a critical neuropeptidergic system that modulates cognitive function, social behavior, and stress responses throughout the brain. While the cell bodies of vasopressin and oxytocin neurons are primarily located in the hypothalamic paraventricular nucleus (PVN) and supraoptic nucleus (SON), these neurons project extensively to cortical and limbic regions, where they release their neuropeptides as volume transmission or synaptic signals to influence synaptic plasticity, memory consolidation, and social cognition [1](https://pubmed.ncbi.nlm.nih.gov/32898456/). In neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD), the vasopressin and oxytocin systems undergo significant alterations that contribute to the characteristic behavioral and cognitive symptoms observed in these disorders [4](https://pubmed.ncbi.nlm.nih.gov/9096745/). The dysfunction of these neuropeptidergic systems has emerged as a potential therapeutic target, with ongoing research exploring oxytocin and vasopressin-based interventions for treating social memory deficits, agitation, and other neuropsychiatric symptoms in dementia patients [8](https://pubmed.ncbi.nlm.nih.gov/31077897/).
The vasopressin and oxytocin neuronal systems originate in the hypothalamus, specifically in the supraoptic nucleus (SON) and paraventricular nucleus (PVN). These nuclei contain magnocellular neurons that synthesize either arginine vasopressin (AVP) or oxytocin (OXT) and project their axons to the posterior pituitary gland for systemic release into the bloodstream [3](https://pubmed.ncbi.nlm.nih.gov/9686351/). However, a separate population of parvocellular neurons in the PVN projects to various brain regions, including the cortex, hippocampus, amygdala, and brainstem, where these neuropeptides act as neuromodulators or neurotransmitters [15](https://pubmed.ncbi.nlm.nih.gov/24139856/). In the human brain, these projections are particularly dense in the entorhinal cortex, hippocampus, and frontal cortical regions—areas critically involved in memory and executive function [5](https://pubmed.ncbi.nlm.nih.gov/9661995/). The distribution of vasopressin and oxytocin fibers in the cortex follows a gradient, with higher densities in limbic-associated regions such as the cingulate cortex and prefrontal cortex, reflecting their primary roles in modulating emotional and social cognitive processes [7](https://pubmed.ncbi.nlm.nih.gov/18203419/).
The effects of vasopressin and oxytocin in the cortex are mediated through specific receptor subtypes. The vasopressin system signals through three G-protein-coupled receptor subtypes: V1a (AVPR1A), V1b (AVPR1B), and V2 (AVPR2). The V1a receptor is the primary mediator of vasopressin's central effects on social behavior, memory, and stress responses, with high expression in the hippocampus, amygdala, and prefrontal cortex [1](https://pubmed.ncbi.nlm.nih.gov/32898456/). The V2 receptor is primarily expressed in the kidney and plays a peripheral role in water regulation, though recent evidence suggests V2 receptors may also have central effects. The oxytocin receptor (OXTR) is similarly expressed throughout the cortex, with particularly high densities in brain regions involved in social cognition, including the anterior cingulate cortex, orbitofrontal cortex, and superior temporal sulcus [12](https://pubmed.ncbi.nlm.nih.gov/35294612/). OXTR expression shows age-related changes that may contribute to the social cognition deficits observed in neurodegenerative diseases, making it a potential biomarker and therapeutic target [8](https://pubmed.ncbi.nlm.nih.gov/31077897/).
Arginine vasopressin (AVP) is a nonapeptide hormone composed of nine amino acids that plays multiple roles in osmotic regulation, blood pressure control, and social behavior. In the brain, AVP acts as a neuropeptide modulator that influences aggressive behavior, social recognition, pair bonding, and memory consolidation through the AVPR1A and AVPR1B receptor subtypes [15](https://pubmed.ncbi.nlm.nih.gov/24139856/). The AVP system is intimately connected with the hypothalamic-pituitary-adrenal (HPA) axis, where it acts synergistically with corticotropin-releasing hormone (CRH) to modulate the stress response. AVP is a more potent stimulator of ACTH release than CRH in some contexts, and this interaction has implications for understanding the chronic stress exposure that characterizes neurodegenerative processes [14](https://pubmed.ncbi.nlm.nih/15152026/). Dysregulation of central AVP signaling has been implicated in the pathophysiology of Alzheimer's disease, where altered AVP levels may contribute to sleep disturbances, agitation, and the disruption of circadian rhythms commonly observed in dementia patients [1](https://pubmed.ncbi.nlm.nih.gov/32898456/).
Oxytocin (OXT) is a structurally related nonapeptide best known for its roles in childbirth and lactation, but which also serves critical functions in the central nervous system as a modulator of social cognition, emotional processing, and stress reactivity [7](https://pubmed.ncbi.nlm.nih.gov/18203419/). Unlike classical neurotransmitters that are released at synaptic terminals, oxytocin is typically released from dendritic stores in a volume-transmission manner, allowing it to act on neurons throughout a local brain region. This non-synaptic release pattern enables OXTR activation to produce prolonged modulatory effects on neuronal networks involved in social behavior. In the cortex, oxytocin reduces anxiety, enhances fear extinction, promotes social recognition, and facilitates trust and prosocial behaviors through its interactions with the amygdala, prefrontal cortex, and hippocampus [8](https://pubmed.ncbi.nlm.nih.gov/31077897/). The oxytocin system has bidirectional interactions with the HPA axis, as acute stress triggers oxytocin release, which in turn exerts anti-stress effects, creating a negative feedback loop that normally promotes stress resilience.
The vasopressin and oxytocin systems undergo substantial alterations in Alzheimer's disease, with evidence pointing to both primary pathological changes and secondary compensatory responses. Post-mortem studies of AD brains have consistently demonstrated significant loss of vasopressin-immunoreactive neurons in the supraoptic nucleus, with some studies reporting up to 50% reduction in AVP neuron numbers compared to age-matched controls [6](https://pubmed.ncbi.nlm.nih.gov/8253534/). This neuronal loss correlates with disease severity and is thought to contribute to the circadian rhythm disturbances, sleep fragmentation, and agitative behaviors seen in AD patients. Interestingly, some studies have found increased vasopressin levels in the cerebrospinal fluid of AD patients, which may represent a compensatory response to neuronal loss or dysregulated release from remaining neurons [17](https://pubmed.ncbi.nlm.nih.gov/26975538/). The oxytocin system shows similar changes, with reduced OXTR binding in key brain regions and decreased CSF oxytocin levels in AD patients, changes that may underlie the social cognition deficits and emotional blunting characteristic of moderate to severe AD [8](https://pubmed.ncbi.nlm.nih.gov/31077897/).
In Parkinson's disease, the vasopressin and oxytocin systems are affected both by the primary neurodegenerative process and by chronic dopaminergic therapy. Parkinson's disease patients frequently exhibit autonomic dysfunction, sleep disorders, and neuropsychiatric symptoms including depression, anxiety, and social withdrawal—all processes modulated by hypothalamic neuropeptides. Studies have found altered vasopressin and oxytocin levels in the CSF of PD patients, with some reports suggesting that these changes correlate with disease duration and severity [10](https://pubmed.ncbi.nlm.nih.gov/34296567/). The dopaminergic system has extensive interactions with hypothalamic nuclei, and dopaminergic neurons in the ventral tegmental area and substantia nigra project to the PVN and SON, creating potential pathways for dopaminergic degeneration to influence neuropeptidergic signaling. Furthermore, levodopa treatment has been shown to modulate vasopressin and oxytocin release, suggesting complex relationships between dopaminergic therapy and neuropeptidergic function that may have clinical implications for managing non-motor symptoms in PD.
Frontotemporal dementia (FTD) presents particularly prominent changes in social cognition and behavior, making the vasopressin and oxytocin systems highly relevant to understanding its pathophysiology. Unlike Alzheimer's disease, which primarily affects memory systems, the behavioral variant of FTD is characterized by profound disruptions in social conduct, empathy, and emotional processing—functions closely tied to neuropeptidergic modulation of the prefrontal cortex and amygdala. Studies have reported altered vasopressin and oxytocin levels in the CSF of FTD patients, with some evidence suggesting that these changes may help distinguish FTD from other dementia types [19](https://pubmed.ncbi.nlm.nih.gov/29980742/). The prominent atrophy and neuronal loss in the frontal and temporal lobes that characterizes FTD likely disrupts the cortical targets of vasopressin and oxytocin projections, potentially leading to downstream effects on receptor expression and neuropeptide homeostasis that contribute to the characteristic behavioral symptoms of the disorder.
Emerging evidence suggests that the vasopressin and oxytocin systems may also be affected in amyotrophic lateral sclerosis (ALS), though research in this area is less extensive. ALS patients frequently exhibit emotional lability (pseudobulbar affect), sleep disturbances, and autonomic dysfunction—symptoms that could involve hypothalamic neuropeptide systems. Some studies have found altered vasopressin and oxytocin levels in the CSF of ALS patients, though the significance of these changes remains unclear. The progressive degeneration of upper and lower motor neurons in ALS may disrupt descending hypothalamic projections that normally modulate spinal cord autonomic neurons, potentially contributing to the respiratory and cardiovascular complications that are a major cause of morbidity in ALS. Further research is needed to clarify the role of these neuropeptides in ALS pathophysiology and whether they represent potential therapeutic targets.
The dysregulation of the oxytocin system in neurodegenerative diseases has prompted interest in oxytocin-based therapeutic interventions. Intranasal oxytocin administration has been explored as a treatment for social cognition deficits in Alzheimer's disease and FTD, with some studies reporting improvements in emotional recognition, social interaction, and caregiver-rated behavior [16](https://pubmed.ncbi.nlm.nih.gov/37433789/). However, the results of clinical trials have been mixed, possibly due to factors including optimal dosing, baseline oxytocin levels, disease stage, and the challenges of delivering neuropeptides across the blood-brain barrier. Animal studies have demonstrated that oxytocin can reduce amyloid-beta-induced neurotoxicity and inflammation, suggesting potential disease-modifying effects beyond symptom management [9](https://pubmed.ncbi.nlm.nih.gov/36119161/). The development of brain-penetrant oxytocin analogs and OXTR agonists represents an active area of pharmaceutical research, with several candidates showing promise in preclinical models of AD and related disorders.
The vasopressin system similarly offers therapeutic opportunities, though its role in neurodegenerative diseases is more complex. Selective V1a receptor antagonists have been explored for their potential to reduce stress-induced neurodegeneration and improve cognitive function in animal models of AD. The rationale for this approach stems from evidence that chronic stress and elevated glucocorticoids accelerate neurodegeneration through mechanisms that involve vasopressin signaling [14](https://pubmed.ncbi.nlm.nih/15152026/). Conversely, some researchers have proposed that vasopressin agonists may have beneficial effects on circadian rhythm regulation and sleep in dementia patients, though this remains controversial. The development of selective receptor subtype ligands with improved brain penetration is an active research area, with the goal of targeting specific aspects of vasopressin signaling without producing unwanted peripheral effects on blood pressure and water retention.
Beyond direct hormone administration, peptide-based strategies targeting the vasopressin and oxytocin systems show promise for neuroprotection in neurodegenerative diseases. The identification of neuroprotective peptide fragments derived from vasopressin and oxytocin sequences has opened new therapeutic avenues [11](https://pubmed.ncbi.nlm.nih.gov/37656543/). These peptide analogs are designed to retain neuroprotective and anti-inflammatory properties while minimizing peripheral hormone effects. Some have shown efficacy in reducing tau phosphorylation, amyloid-beta toxicity, and neuroinflammation in cellular and animal models. The pepan peptide and related compounds represent a novel class of neuroprotective agents that may benefit from further clinical development for Alzheimer's disease and related disorders. Additionally, strategies targeting the receptors themselves—such as allosteric modulators of OXTR and AVPR1A—offer potential for more selective modulation of neuropeptidergic signaling with fewer side effects.
Cerebrospinal fluid (CSF) analysis remains the primary method for assessing central vasopressin and oxytocin levels in vivo. Radioimmunoassay (RIA) and enzyme immunoassay (EIA) techniques have been developed to measure AVP and OXT concentrations in small volumes of CSF, enabling correlation with clinical parameters and disease status [17](https://pubmed.ncbi.nlm.nih.gov/26975538/). Studies have demonstrated decreased CSF oxytocin levels in AD and FTD patients compared to healthy controls, with some evidence suggesting that CSF oxytocin may correlate with social cognition performance. However, the interpretation of CSF neuropeptide levels is complicated by factors including diurnal variation, sample collection methods, and the compartmentalization of neuropeptides between CSF and brain tissue. The development of more sensitive and specific assays, along with standardized collection protocols, will improve the utility of CSF neuropeptide measurement as a biomarker for neurodegenerative disease diagnosis and progression.
Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) can be used to visualize receptor binding in vivo, providing information about OXTR and AVPR1A availability in the brains of living patients. These studies have demonstrated reduced OXTR binding in the brains of AD patients, particularly in regions involved in social cognition, though the specificity of these changes as biomarkers remains to be established. Functional MRI studies have examined the neural correlates of oxytocin administration in AD patients, showing effects on amygdala reactivity and functional connectivity in social processing networks. The combination of receptor imaging with clinical and cognitive measures may help identify patients who are most likely to benefit from oxytocin-based therapies and enable monitoring of treatment responses.
Post-mortem brain tissue analysis remains essential for understanding the anatomical and cellular changes in vasopressin and oxytocin systems in neurodegenerative diseases. Immunohistochemical studies have quantified neuron numbers, fiber densities, and receptor expression in key brain regions, providing insights into the structural basis of neuropeptidergic dysfunction [5](https://pubmed.ncbi.nlm.nih.gov/9661995/). These studies have demonstrated loss of vasopressin neurons in the hypothalamus of AD patients, reduced OXTR binding in the cortex and amygdala, and altered expression of both neuropeptides and their receptors in affected brain regions. Molecular studies have examined gene expression and epigenetic modifications in hypothalamic neurons, providing insights about the mechanisms underlying neuropeptidergic dysfunction. The availability of well-characterized brain tissue banks has facilitated these studies and will continue to be important for validating biomarkers and understanding disease mechanisms.
The paraventricular nucleus of the hypothalamus (PVN) serves as the primary source of vasopressin and oxytocin neurons that project to cortical regions. The PVN contains both magnocellular and parvocellular neurosecretory neurons, with the parvocellular population providing the majority of cortical projections [@soontornmal_schulte_2020]. These parvocellular neurons synthesize vasopressin and oxytocin and release them from axonal terminals in target regions, functioning as neuromodulators rather than classical neurohormones.
The PVN projects to cortical regions through multiple pathways, including the medial forebrain bundle and direct hypothalamic-cortical projections. These projections terminate preferentially in layers I and V of the prefrontal cortex, the stratum radiatum of the hippocampus, and the basal lateral amygdala. The density of these projections shows regional variation, with the medial prefrontal cortex and anterior cingulate cortex receiving the densest innervation [@seeley2009].
The supraoptic nucleus (SON) provides additional vasopressin and oxytocin projections to cortical targets, particularly the temporal lobe structures involved in memory processing. SON neurons project to the entorhinal cortex and perirhinal cortex, regions critical for declarative memory consolidation [@laws2007]. These projections are thought to modulate the consolidation of social and emotional memories, linking hypothalamic neuropeptide release to cortical memory systems.
Beyond the PVN and SON, several accessory neurosecretory nuclei contain vasopressin and oxytocin neurons that contribute to cortical projections. These include the nucleus circularis, the bed nucleus of the stria terminalis (BNST), and various periventricular cell groups. The BNST, in particular, serves as a relay station for hypothalamic-neuropeptide projections to the prefrontal cortex and is itself affected in Alzheimer's disease [@poblete2022].
The vasopressin system signals through three G-protein-coupled receptor subtypes: V1a (AVPR1A), V1b (AVPR1B), and V2 (AVPR2). The V1a and V1b receptors are expressed in the brain and mediate the central effects of vasopressin. AVPR1A shows high expression in the prefrontal cortex, hippocampus, and amygdala, regions that receive vasopressinergic projections and are implicated in neurodegeneration [@schmidt2020].
In Alzheimer's disease, AVPR1A expression is altered in the prefrontal cortex, with some studies showing increased receptor density in early disease stages as a compensatory response, followed by progressive reduction in later stages [@jensen2021]. These changes parallel the pattern of neurodegeneration and may contribute to the social cognition and memory deficits that characterize AD.
Oxytocin receptor (OXTR) expression in the cortex shows a distribution pattern similar to vasopressin receptors, with high expression in the prefrontal cortex, cingulate cortex, hippocampus, and amygdala. OXTR is a G-protein-coupled receptor that primarily signals through Gq-mediated pathways, leading to increased intracellular calcium and modulation of neuronal excitability [@liao2021].
Studies of OXTR expression in AD have revealed reduced receptor density in several cortical regions, potentially contributing to the social cognition deficits observed in patients. Genetic variants in OXTR have been associated with altered social behavior in AD, suggesting that individual differences in neuropeptide signaling may influence disease manifestation [@engelman2022].
Cortical vasopressin and oxytocin neurons play essential roles in social cognition, the collection of cognitive processes that enable individuals to perceive, interpret, and respond to social stimuli. The prefrontal cortex, particularly the medial prefrontal cortex, integrates neuropeptide signals to regulate social recognition memory, emotional empathy, and social decision-making [@turen2008].
Vasopressin in the prefrontal cortex promotes social recognition memory, enabling individuals to identify and remember conspecifics. Oxytocin complements this function by enhancing trust, facial recognition, and emotional empathy. The interaction between these systems in the prefrontal cortex creates a nuanced modulation of social behavior that is disrupted in neurodegenerative diseases.
Both vasopressin and oxytocin modulate memory consolidation, though their effects differ depending on the type of memory and brain region. In the hippocampus, vasopressin enhances spatial memory consolidation while oxytocin may impair it, reflecting the complementary roles of these neuropeptides in different memory systems [@mcnay2007].
The projection from hypothalamic vasopressin neurons to the entorhinal cortex provides a route through which neuropeptide signaling influences the consolidation of declarative memories. This pathway may be particularly relevant to the early memory deficits in AD, as the entorhinal cortex is among the first regions to show tau pathology.
Cortical vasopressin and oxytocin neurons participate in the modulation of stress responses through their projections to the prefrontal cortex and hippocampus. Vasopressin generally promotes anxiogenic responses, while oxytocin exerts anxiolytic effects. The balance between these systems influences hypothalamic-pituitary-adrenal (HPA) axis activity and cortisol release [@faber2021].
The prefrontal cortex regulates HPA axis activity through top-down control, and neuropeptide modulation of this region influences stress reactivity. In neurodegenerative diseases, dysregulation of these systems may contribute to the behavioral and psychological symptoms of dementia, including agitation, anxiety, and depression.
Multiple studies have documented alterations in vasopressin and oxytocin levels in the cerebrospinal fluid and plasma of AD patients. CSF vasopressin levels show a characteristic pattern of early increase followed by decline in moderate to severe disease stages, while oxytocin levels are generally reduced throughout disease progression [@zhou2021]. These changes reflect the degeneration of hypothalamic neuropeptide neurons and may contribute to the cognitive and behavioral symptoms of AD.
Postmortem studies have revealed reduced numbers of vasopressin and oxytocin neurons in the PVN and SON of AD patients, particularly in cases with severe cognitive impairment [@popplewell2021]. This neuronal loss may result from tau pathology affecting hypothalamic neurons, as the PVN and SON show early involvement in the spread of neurofibrillary pathology.
The expression of vasopressin and oxytocin receptors in cortical regions is altered in AD, reflecting both compensatory responses to changed neuropeptide levels and direct effects of pathology on receptor-expressing neurons. AVPR1A density in the prefrontal cortex shows complex changes across disease stages, while OXTR density is generally reduced, particularly in the cingulate cortex [@schmidt2020].
These receptor changes have functional consequences, as they alter the responsiveness of cortical neurons to neuropeptide signaling. The net effect may be a disruption of the fine-tuned neuropeptide modulation of cognition and behavior that characterizes the healthy brain.
The social cognition deficits that develop in AD, including impaired facial recognition, reduced emotional empathy, and altered social behavior, may be partly attributable to disruption of the cortical vasopressin and oxytocin systems. The loss of hypothalamic neuropeptide neurons and the accompanying changes in receptor expression disrupt the normal modulation of prefrontal cortex function by these neuropeptides [@poblete2022].
Studies in frontotemporal dementia have shown particularly prominent social cognition deficits, reflecting the specific vulnerability of frontal and temporal brain regions that receive dense vasopressin and oxytocin innervation. Interestingly, intranasal administration of oxytocin has been explored as a potential treatment for social cognition deficits in FTD, with some positive results [@rosch2020].
Parkinson's disease affects hypothalamic function through multiple mechanisms, including direct alpha-synuclein pathology, Lewy body formation in hypothalamic nuclei, and disruption of autonomic regulatory centers. Studies have documented reduced vasopressin and oxytocin neuron numbers in the PVN and SON of PD patients, with these changes correlating with autonomic dysfunction symptoms [@hernandez2022].
The autonomic dysfunction in PD, including orthostatic hypotension, urinary dysfunction, and sleep disorders, reflects hypothalamic involvement that extends to neuropeptide-producing neurons. The loss of vasopressin neurons may contribute to electrolyte imbalances and blood pressure dysregulation, while oxytocin neuron loss may affect social behavior and stress responses.
Social cognition deficits are increasingly recognized in Parkinson's disease, even in early stages before significant dementia develops. These deficits include impaired facial emotion recognition, reduced theory of mind, and altered social decision-making. The cortical vasopressin and oxytocin systems likely contribute to these deficits, though their specific role remains under investigation [@fischer2021].
The vulnerability of dopaminergic neurons in PD may indirectly affect neuropeptide signaling, as dopamine modulates the activity of hypothalamic neuropeptide neurons. The loss of dopaminergic input to the hypothalamus may contribute to the dysregulation of vasopressin and oxytocin systems.
Hypothalamic vasopressin and oxytocin neurons show early vulnerability to tau pathology, with neurofibrillary tangles detected in these nuclei in early AD cases. The PVN and SON are located in brain regions that develop tau pathology relatively early in the disease process, consistent with the pattern of AD neuropathology progression [@lucin2019].
The susceptibility of hypothalamic neurons to tau pathology may relate to their high metabolic activity, extensive axonal projections, and the specific tau isoform expression patterns in these cells. The degeneration of these neurons contributes to the disruption of neuropeptide signaling that characterizes AD.
The loss of hypothalamic neuropeptide neurons and their cortical projections has downstream effects on cortical function. Without proper neuropeptide modulation, prefrontal cortex neurons show altered activity patterns that may contribute to cognitive deficits. The interaction between neuropeptide signaling and other neurotransmitter systems, including glutamate and GABA, creates complex effects on cortical processing.
Neuroinflammation in AD affects both hypothalamic neurons and their cortical targets, creating a bidirectional relationship between neuropeptide dysregulation and inflammatory processes. The hypothalamus shows prominent microglial activation in AD, which may contribute to neuropeptide neuron degeneration [@lucin2012019].
The involvement of vasopressin and oxytocin systems in AD suggests potential therapeutic approaches. Intranasal administration of oxytocin has been explored in clinical trials for AD and FTD, with some evidence of improved social cognition and reduced agitation. Similarly, vasopressin receptor agonists and antagonists have been investigated for their cognitive effects.
The challenge with neuropeptide-based therapies lies in the complexity of the system and the need to achieve region-specific effects without causing systemic side effects. Targeting specific receptor subtypes or developing biased agonists that activate desired signaling pathways may provide more selective therapeutic effects.
The measurement of vasopressin and oxytocin in CSF and plasma offers potential as biomarkers of disease progression in AD and PD. Changes in neuropeptide levels may reflect hypothalamic neurodegeneration and could serve as indicators of disease stage or treatment response. However, the variability in neuropeptide measurements and the influence of peripheral sources limit their current clinical utility.
Related Hypotheses: