Neurobiological factors influencing the restless legs syndrome
The relationship between low iron and RLS is one of the most critical factors in understanding the RLS condition. Iron regulates dopamine in the basal ganglia, in the brain (see Figure 1 for anatomical location of the basal ganglia), regulating smooth muscle movement (also has other functions). Low iron in the basal ganglia leads to low dopamine and subsequently RLS.
It is not always just a lack of dopamine, but also rather a complex dysfunction in the down regulation of dopamine receptors (D2R and D3) that causes the neurological urge to move. In RLS dopamine receptor reduction is reportedly caused by an excessive amount of presynaptic dopamine being produced during daytime. This elevated dopamine results in the downregulation of dopamine receptors.
In summary RLS is caused / worsened by low dopamine combined with a double whammy of low numbers of dopamine receptors. This crash in dopamine regulation then reduces the inhibition of sensory / motor signals to the extremities leading to the uncomfortable sensation and irresistible urge to move.
Is low iron causing my restless legs syndrome?
Iron is a fundamental requirement for brain chemistry regulating movement. Low to normal iron levels can produce RLS.
Figure 3: Nerve synapse showing dopamine release, reuptake and receptor binding
The role of Dopamine in the restless legs syndrome
Researchers have identified that in people with RLS there is an imbalance of dopamine in the brain. Dopamine is involved in the transmission of messages from the basal ganglia involved in smoothing and regulating movement. Likely due to the endogenous circadian rhythm (body clock), RLS symptoms tend to worsen at night due to low dopamine. This is often exacerbated by low brain iron levels (see Iron section above), which are necessary for dopamine production.
Figure 2: Chemical structure of dopamine
Iron is a necessary "cofactor" for an enzyme called tyrosine hydroxylase. This enzyme is responsible for producing dopamine in the brain. So low iron leads to low tyrosine hydroxylase such that the result is a reduced amount of dopamine in turn leading to RLS. Since dopamine is the neurotransmitter that controls smooth, purposeful muscle movement, a lack of it leads to the "misfiring" signals yielding the crawling, tingling, and irresistible urge to move characterizing RLS.
As well as reducing the amount of available dopamine iron regulates dopamine transporters and receptors levels in the substantia nigra. The substantia nigra is a small brain region in the midbrain that plays a major role in:
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Controlling and coordinating movement
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Starting voluntary movements
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Learning habits and motor skills
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Motivation, reward and reinforcement
The substantia nigra pars compacta produces dopamine and sends it to the striatum, part of the basal ganglia. This dopamine helps movement circuits operate smoothly. A low iron level downregulates dopamine receptor functionality destabilizing movement control loops causing / worsening RLS.
Hepcidin is a hormone that regulates iron absorption. Its levels naturally rise in the evening and at night. When hepcidin is high (evening), it blocks iron from entering the bloodstream. This may be one reason why RLS symptoms typically peak at night. The brain is essentially "starved" of a fresh iron supply right when it needs it most.
For the general population, a ferritin level of 30 μg/L might be considered "normal." However, for someone with RLS, medical guidelines often suggest keeping ferritin levels above 75 μg/L or even 100 μg/L to manage symptoms. Although iron is an over-the-counter medication too much iron can be harmful. Getting an iron studies blood test and consulting with a healthcare professional before starting or changing iron supplements is recommended.
Figure 1: (a) Sagittal and (b) Axial view of MRI image showing the basal ganglia in blue.
What role does Glutamate play in the restless legs syndrome?
Glutamate is the principal excitatory neurotransmitter in the central nervous system (CNS) acting like the brain's accelerator pedal. Iron and dopamine have long been the key players in understanding RLS causes. However, glutamate is emerging as a key neurotransmitter regulating the severity of the symptoms, the nighttime restlessness, and the overall hyperarousal state in RLS. Genetic and neuroimaging studies indicate that persons with genetic predispositions for RLS have a presynaptic hyperglutamatergic state (the neurons produce too much glutamate, particularly at night). There is also reduced synaptic inhibition of glutamate further elevating glutamate. The increased excitation caused by excess glutamate overstimulates the cortico-striatal-thalamic-cortical circuit (the brain loop regulating movement, sensory processing, and sleep arousal), creating that disruptive, "creepy crawly" intense sensation with an urge to move.
When glutamate levels are abnormally high the brain struggles to suppress minor physical sensations, leading to the crawling, itching, or pulling feelings in the legs. High glutamate drives the uncontrollable urge to move the limbs to relieve those sensations. Normally, glutamate levels drop at night to allow deep, restful sleep. In individuals with RLS, glutamate levels remain elevated throughout the night, causing persistent micro-arousals (very brief awakenings) and a state of central hyperarousal where the brain remains alert even during rest. It is possible that this arousal state further disrupts sleep leading to daytime somnolence.
Figure 4: Glutamate chemical structure
Glutamate doesn't act in isolation; it interacts directly with brain iron deficiency and dopamine signaling. Iron deficiency reduces dopamine receptor function. Dopamine normally helps to inhibit excessive glutamate release. When dopamine regulation fails, glutamate signaling goes into overdrive, causing sensorimotor hyperexcitability.
Figure 5: Glutamate presynaptic release and reuptake. Post synaptic receptors.
Did you know coffee is bad for the restless legs syndrome (RLS). Look at your coffee intake. Caffeine keeps people awake by acting as a molecular "mute button" for the brain’s fatigue signals. It does not actually provide the body with energy; rather, it prevents the brain from receiving the chemical message that you are tired. Throughout the day, as the brain neurons fire, they produce adenosine as a byproduct. Adenosine builds up over the course of the day and binds to specific receptors (A1 and A2A Receptors) in the brain, signaling to the body that it is time to slow down and rest. This is known as "sleep pressure." Because caffeine’s molecular structure is very similar to adenosine, it can "sneak" into the adenosine receptors. Caffeine stops adenosine from binding. Because caffeine does not trigger the same slowing-down effect as adenosine, the brain remains in an alert state, unaware of the mounting fatigue. This lack of sleep pressure makes it hard to fall asleep if there is caffeine in your system. Also the arousal state caused by caffeine stimulates the "irresistible urge" to move the legs and make the uncomfortable sensations associated with the RLS feel more pronounced.
Did you know that the foods you eat may influence the Restless Legs Syndrome (RLS). Firstly, there are some foods to avoid namely drinks containing caffeine (e.g., coffee, energy drinks). Alcohol interferes with sleep cycles including the circadian rhythm. This worsens RLS. High-sugar diets and highly processed foods are linked to inflammation, which may negatively impact RLS symptoms. There are some foods that may help relieve some of the RLS leg discomfort and the urge to move. Iron is a critical factor in RLS. Red meat, poultry, seafood, beans, lentils, and iron-fortified cereals are all high in iron. Magnesium helps muscles relax and supports proper nerve function. Foods containing magnesium include almonds, cashews, peanuts, spinach, edamame, and black beans. Folate (B9) is essential for healthy nerve and cell function. Dark leafy greens (spinach), liver, and legumes are sources of Folate. Potassium aids in muscle contraction and nerve impulses. Foods containing potassium include Bananas, leafy greens, and various fruits/vegetables. So eat well and hopefully the RLS will reduce.
The role of adenosine in restless legs syndrome
Adenosine is a neuromodulator that accumulates in the brain during wakefulness and contributes to sleep pressure and reduced neuronal excitability. One particularly important receptor is the adenosine A1 receptor (A1R). Activation of A1 receptors generally puts a brake on neuronal activity, including glutamate and dopamine signalling.
Adenosine may be an important link between brain iron deficiency, dopamine, glutamate, sleep disturbance and the urge to move in restless legs syndrome (RLS). This is known as the adenosine hypothesis of RLS. It is a compelling model, but it is still a hypothesis rather than a completely proven explanation of RLS. Researchers propose that RLS involves a hypoadenosinergic state—in effect, insufficient adenosine signalling.
Figure 6: Flow chart of the adenosine hypothesis for RLS
A1 receptors normally inhibit glutamate release from corticostriatal nerve terminals. When A1 receptors are reduced, these terminals become more sensitive and glutamate transmission can become excessive. Adenosine therefore may not simply be another neurotransmitter involved in RLS. It may be one of the mechanisms connecting iron deficiency to the dopamine and glutamate abnormalities seen in the disorder.
For more information on risk factors for RLS see the pages below:
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Medical disorders that are a risk factor for RLS
Exploding Head Syndrome (EHS) is a recognized, generally harmless sleep disorder. People who experience EHS perceive a sudden, exceptionally loud noise that seems to originate from inside or right outside their head. Because it is a sensory hallucination tied to the sleep-wake transition, no one else can hear it. An episode typically lasts just a split second, but it is frequently accompanied by physiological and psychological reactions due to the sudden shock. For most people, the most effective "treatment" is simply understanding what EHS is. Realizing that the condition is benign and not a sign of a stroke, brain tumour, or mental illness drastically reduces the anxiety surrounding it. When episodes of EHS are frequent or disruptive, management typically focuses on: improving sleep hygiene and stress reduction. In rare, severe cases where sleep is chronically disrupted, doctors may occasionally prescribe medications that stabilize neurological activity (such as certain anti-seizure drugs or tricyclic antidepressants).
Last reviewed: 06/09/2026