The Body's Thermostat: How Temperature Is Regulated
Normal human body temperature is tightly regulated within a narrow range, typically around 98.6°F (37°C), although this can vary slightly from person to person. The hypothalamus, a small but vital region of the brain, acts as the body's main thermoregulatory center. It constantly receives signals from temperature-sensitive nerves throughout the body and adjusts processes like shivering and sweating to maintain a stable core temperature. Illnesses can interfere with this complex system in various ways, either by affecting the hypothalamus directly or by disrupting the metabolic and hormonal functions that generate body heat.
Metabolic and Endocrine Disorders
Endocrine glands produce hormones that regulate many bodily functions, including metabolism, which is the process of generating heat. When these systems are out of balance, a drop in body temperature can occur.
Hypothyroidism
An underactive thyroid gland, or hypothyroidism, is a common culprit behind a consistently low body temperature. The thyroid produces hormones that control the body's metabolic rate, essentially acting as its internal furnace. With insufficient thyroid hormone, metabolism slows, and the body generates less heat, causing the individual to feel cold all the time. Other symptoms include fatigue, weight gain, depression, and dry skin.
Hypoglycemia
Severe hypoglycemia, or dangerously low blood sugar, is another illness that can cause a drop in body temperature. Glucose is the body's primary fuel, and when levels are too low, the body lacks the energy needed for normal functions, including temperature regulation. As blood sugar drops, the body may inhibit shivering—a key heat-producing mechanism—to conserve energy, further lowering core temperature. This can occur in individuals with diabetes or other conditions that affect blood sugar control.
Adrenal Insufficiency
Also known as Addison's disease, adrenal insufficiency occurs when the adrenal glands don't produce enough cortisol. Cortisol is a stress hormone that also plays a role in blood pressure, glucose metabolism, and temperature regulation. Insufficient cortisol can impair the body's ability to maintain a stable temperature, particularly during physiological stress. Hypothermia in patients with adrenal insufficiency can be a sign of a life-threatening adrenal crisis.
Systemic Infections and Sepsis
While infections most often cause a fever, a severe systemic infection like sepsis can result in a low body temperature, particularly in older adults or those with compromised immune systems. Sepsis is the body's extreme inflammatory response to an infection that can lead to organ dysfunction and a dangerous drop in blood pressure. The occurrence of hypothermia during sepsis is often a negative prognostic sign, indicating a severe, overwhelming infection and a weakened immune response.
Neurological Conditions
The hypothalamus's role in temperature regulation makes it vulnerable to neurological damage. Conditions that affect the central nervous system can impair the body's ability to sense and respond to temperature changes.
- Stroke: A stroke, particularly one affecting the hypothalamus or related brain structures, can directly disrupt the brain's ability to regulate temperature.
- Spinal Cord Injury: Injuries, especially those at the T6 level or higher, can disconnect the brain from the rest of the nervous system, impairing the body's ability to sense temperature changes and shiver effectively.
- Parkinson's Disease and Multiple Sclerosis: These neurodegenerative disorders can affect the autonomic nervous system, leading to impaired thermoregulation.
Other Contributing Factors
Beyond specific illnesses, several other factors can exacerbate or cause low body temperature:
- Medications: Some drugs, including certain antidepressants, antipsychotics, sedatives, and opioids, can alter the body's thermoregulation.
- Malnutrition and Anorexia Nervosa: Severe malnutrition and eating disorders can lead to decreased body fat and metabolic rate, resulting in reduced heat production.
- Advanced Age: As we age, our bodies become less efficient at regulating temperature, and the ability to sense cold diminishes. This makes older adults more vulnerable to hypothermia.
- Alcohol and Drug Use: Alcohol causes vasodilation, increasing heat loss from the skin, and impairs judgment, making individuals less likely to seek shelter in cold conditions.
Comparison of Illnesses Causing Low Body Temperature
| Illness | Primary Mechanism | Associated Symptoms | Key Risk Factor | Urgency |
|---|---|---|---|---|
| Hypothyroidism | Slowed metabolism due to insufficient thyroid hormone. | Fatigue, weight gain, dry skin, depression. | Gradual hormonal imbalance. | Often managed with medication, but requires a diagnosis. |
| Sepsis | Overwhelming systemic infection and inflammatory response. | Fever (often initially), chills, confusion, rapid heart rate, low blood pressure. | Active infection, weakened immune system. | Medical emergency; requires immediate attention. |
| Neurological Disorders | Damage to or dysfunction of the hypothalamus. | Vary depending on the condition (e.g., paralysis with SCI, tremor with Parkinson's). | Brain or spinal cord injury, neurodegenerative disease. | Varies depending on condition, but requires medical care. |
| Severe Hypoglycemia | Lack of glucose (energy) to power thermoregulation. | Shakiness, sweating, confusion, dizziness, fatigue. | Diabetes, poor blood sugar control. | Medical emergency, especially if unconscious. |
| Adrenal Insufficiency | Inadequate cortisol production. | Weakness, low blood pressure, gastrointestinal symptoms. | Adrenal gland dysfunction or crisis. | Medical emergency if in adrenal crisis. |
When to Seek Medical Attention
A slightly low temperature is not always cause for concern. However, if your body temperature consistently registers below 97°F (36.1°C) or drops below 95°F (35°C), it could signal a serious medical problem and requires immediate attention. It is especially critical to seek emergency care if low temperature is accompanied by symptoms such as confusion, slurred speech, shallow breathing, weak pulse, or loss of consciousness.
Conclusion
While exposure to cold is the most common cause of hypothermia, a range of underlying illnesses can also significantly lower body temperature. Endocrine disorders, severe infections, and neurological conditions can all interfere with the body's delicate thermoregulation system. Consulting a healthcare provider is essential for anyone experiencing a persistently low body temperature to determine the root cause and receive appropriate treatment. For more detailed information on various conditions, you can refer to authoritative sources like the Mayo Clinic.
