You're Overheating When Everyone Else Is Fine. Here's Why.

COMT (catecholamine O-methyltransferase) is an enzyme that breaks down and clears dopamine, epinephrine (adrenaline), and norepinephrine from your brain and bloodstream. Think of it as your nervous system’s cleanup crew. When COMT is working normally, these stress hormones get processed quickly, and your body returns to baseline. When they’re cleared slowly, these hormones accumulate.

If you carry the slow COMT variant (Val158Met homozygous), your body is roughly 40% slower at clearing stress hormones compared to people with the fast variant. This means even mild heat exposure or emotional stress triggers a sustained adrenaline surge that your body can’t efficiently clear. That surge drives rapid heartbeat, flushing, excessive sweating, and the sensation that your core temperature is spiking.

You probably notice that you overheat most during stressful situations, in crowded spaces, or when you’re anxious. You might feel your heart racing before the sweating starts. You probably can’t tolerate caffeine, and high-stress environments push you to physical limits faster than others. This isn’t anxiety alone, it’s a cascade that starts with stress hormones your body can’t quickly remove.

DIO2 (deiodinase type 2) is the enzyme responsible for converting T4 (the inactive form of thyroid hormone) into T3 (the active form that your cells actually use). Your thyroid produces T4, but it’s inert until DIO2 converts it. DIO2 works in virtually every tissue in your body, but it’s especially active in your brain, brown fat, and muscles. When DIO2 is working well, you maintain stable body temperature and healthy energy production. When it isn’t, you feel cold, fatigued, or paradoxically, overheated.

The DIO2 Thr92Ala variant, carried by roughly 12-15% of the population, impairs this conversion process. You can have perfectly normal TSH and T4 levels on standard bloodwork and still be functionally hypothyroid at the cellular level because your tissues aren’t producing enough active T3. This impaired T3 production destabilizes your core temperature set-point. Your body loses its ability to regulate heat efficiently, leading to either heat intolerance or erratic temperature swings.

You probably notice that despite normal thyroid bloodwork, you still feel cold in some contexts but overheat in others. Your metabolism feels sluggish. You might gain weight easily or struggle to lose it. When you overheat, the sweating feels disproportionate to the actual temperature. This is what tissue-level hypothyroidism feels like.

ESR1 (estrogen receptor alpha) is the primary estrogen receptor in your hypothalamus, the part of your brain that controls your thermostat. Estrogen is one of the most powerful regulators of body temperature. It directly affects the hypothalamic set-point that tells your body when to sweat, when to generate heat, and when to cool down. Variations in ESR1 change how sensitively your hypothalamus responds to circulating estrogen levels.

Roughly 40% of the population carries ESR1 variants (PvuII, XbaI) that reduce estrogen receptor sensitivity or alter estrogen signaling efficiency. With reduced ESR1 sensitivity, your hypothalamus becomes dysregulated, leading to erratic temperature responses, excessive sweating, and flushing even when estrogen levels are technically normal. This is why perimenopausal and menopausal women often describe feeling like their thermostat is broken. It is, in a sense. The receptor responsible for interpreting estrogen’s temperature-regulating signal isn’t working optimally.

You probably notice that your heat intolerance fluctuates with your menstrual cycle (if you menstruate) or with hormonal changes. Flushing and night sweats may be prominent. You might overheat in situations that don’t seem to bother others, and cooling down takes longer. If you’re in perimenopause or menopause, this symptom may have intensified dramatically.

MTHFR (methylenetetrahydrofolate reductase) is the enzyme that converts dietary folate into methylfolate, the form your cells actually use. This enzyme is critical for methylation reactions throughout your body, including the synthesis of neurotransmitters, detoxification pathways, and the regulation of inflammation. MTHFR is also involved in thyroid antibody metabolism and the function of selenium-dependent thyroid enzymes. When MTHFR is compromised, B vitamin insufficiency cascades throughout your system.

The MTHFR C677T variant, carried by roughly 40% of people with European ancestry, reduces enzyme efficiency by roughly 35-40%. This means your cells are functionally depleted of methylfolate and other activated B vitamins, even if you’re eating a perfect diet. Cellular energy production slows, mitochondrial function deteriorates, and your ability to regulate inflammation and temperature becomes compromised. Additionally, impaired methylation affects thyroid function and the production of heat-shock proteins that help your body manage thermal stress.

You probably notice that you feel better when you eat specific foods, and worse when you miss certain micronutrients. You might have a history of anxiety or mood sensitivity. You likely feel exhausted despite adequate sleep. When you overheat, recovery takes longer than it should. This is methylation insufficiency compounded by poor mitochondrial capacity.

VDR (vitamin D receptor) is the protein that allows your cells to respond to vitamin D signaling. Vitamin D is far more than a bone-health molecule. It’s a hormone that regulates calcium signaling, immune function, neuromuscular control, and thermoregulation. Your hypothalamus uses calcium signaling to maintain your core temperature set-point. When VDR signaling is compromised, calcium regulation becomes dysregulated, and your thermostat loses precision.

VDR variants (BsmI, FokI polymorphisms) are present in roughly 30-50% of the population, and they determine how efficiently your cells can use the vitamin D you’re producing or supplementing. With less efficient VDR signaling, even if your 25-OH vitamin D level is technically “normal,” your cells aren’t responding to that vitamin D appropriately, and calcium-dependent thermoregulation falters. The result is a thermostat that overshoots in both directions: cold intolerance mixed with heat intolerance, or erratic temperature swings.

You probably notice that supplementing with regular vitamin D hasn’t dramatically improved how you feel, even though your bloodwork suggests you’re sufficient. You might experience muscle twitches or cramping, which suggests calcium dysregulation. Your temperature regulation feels unpredictable, and you’re unsure whether you’ll be too hot or too cold.

SOD2 (superoxide dismutase 2) is a critical antioxidant enzyme that works inside your mitochondria to neutralize free radicals and prevent oxidative damage. Your mitochondria are the power plants of your cells, and they’re constantly generating small amounts of free radical byproducts. SOD2 is the cleanup enzyme that prevents those byproducts from damaging the machinery. When SOD2 is functioning well, mitochondria stay healthy and produce energy efficiently. When it’s compromised, oxidative stress accumulates inside the mitochondria.

SOD2 variants (Ala16Val, rs4880) occur in roughly 30-40% of the population and reduce the efficiency of the SOD2 enzyme. With reduced SOD2 function, your mitochondria experience chronic oxidative stress, which impairs energy production and destabilizes your body’s ability to maintain consistent core temperature. Heat intolerance often accompanies this because overheating generates even more mitochondrial free radicals, triggering a cascade of cellular stress that your antioxidant system can’t handle.

You probably notice that heat exposure leaves you feeling disproportionately exhausted, not just uncomfortably warm. Recovery after sweating feels slow. You might experience post-exertional malaise or feel worse after pushing yourself physically. Your fatigue has a cellular quality to it, distinct from just being tired.