The Significance of Body Temperature and Thermoregulation

Maintaining body temperature or thermoregulation is a vital part of homeostasis — keeping balance within the body. In warm-blooded creatures like humans, thermoregulation keeps the core internal temperature within a safe range, regardless of how cold or hot it is outside the body. A person's body temperature must remain within that safe range for their internal cells and organisms to survive. When the body gets too hot or too cold and this goes unaddressed, a person may experience organ failure.

The hypothalamus is the part of the brain in charge of thermoregulation and is often referred to as the body's thermostat. The hypothalamus has messengers all around the body that sense temperature changes and report back. When the thermostat senses the body is getting too hot, it sends signals to areas responsible for sweating, activating our built-in cooling system. Likewise, when the body gets too cold, the hypothalamus triggers shivering, trembling, and the pumping of blood to the internal organs to keep them protected from the cold.

During illness, measuring a person’s body temperature is vital, as it can indicate issues that might cause concern. Thermometers are the most-used option, and range from ones kept in the bathroom vanity to the more industrial versions used by doctors. The mouth is the most common place from which to take a temperature, though the rectum, armpit, inside the ear, or on the forehead over the temporary artery. Medical professionals consider rectal temperature the most accurate. Some thermometers measure within seconds and provide results digitally, while others can take a few minutes and require knowledge of how to read the results.

The average human body temperature is 98.6°F or 37°C, and experts consider fluctuations of plus or minus 1°F to be normal. In 2020, research from Stanford University’s School of Medicine compared the average body temperatures of Americans from 1860 to 1940, from 1971 to 1975, and from 2007 to 2017. They found that the average body temperature has decreased by 0.03°C over each decade. They also found that older subjects had higher body temperatures than younger subjects whose temperatures were taken on the same day. This is likely because younger generations have had more vaccinations and less exposure to infections.

Even in a normal, healthy person, body temperature can fluctuate due to age, gender, activity, time of the month, and even the time of day. Higher levels of activity and lower levels of hydration may cause fluctuations, and body temperature is usually lower in the morning and higher in the afternoon. Temperatures may also spike during a stressful or emotional event. In addition, body temperature is closely linked to hormone production; some women have a higher temperature during their period. It also means that hormone regulation problems, such as those caused by thyroid disorders, may experience significant changes in overall core body temperature.

Normally, a temperature slightly below average is nothing to be concerned about unless it’s consistently low or close to 95°F. Reduced production of hormones from the thyroid, pituitary gland, or adrenal glands can cause a low body temperature. So, too, can nervous system disorders that interfere with communication to the hypothalamus, such as a stroke, Parkinson’s disease, multiple sclerosis, or brain tumors involving the hypothalamus. Serious infections such as sepsis or pneumonia can also trigger a lower-than-normal body temperature, as can certain medications and malnutrition.

Hypothermia is when the hypothalamus has lost its ability to maintain body temperature and keep the body warm enough. A person with a temperature below 95°F or 35°C is likely to be diagnosed with this condition. Being outside in freezing cold weather, in a house with no heating, or immersion in cold water (such as falling into a frozen pond) can cause hypothermia. As the body gets colder, organs start to slow down, causing shivering, slurred speech, shallow breathing, a weak pulse, confusion, drowsiness, memory loss, and clumsiness.

Although fevers usually go away on their own, they also signify a problem in the body — often a viral or bacterial infection or illness. Medicine, particularly antibiotics and blood pressure medications, and medical conditions such as heat exhaustion, arthritis, heart attack, hyperthyroidism, and arthritis can calso cause a fever. In these cases, the hypothalamus does not alter body temperature; rather, the immune system raises the internal temperature in an attempt to kill off the foreign bodies. Temperatures of 100.4°F (38°C) (101°F if taken rectally) indicate a fever. If the symptom persists for more than a day, or becomes worse, it is best to see a doctor.

Hyperthermia occurs when the body's thermostat loses its ability to keep things cool. This can occur if a person is overheated from exerting too much energy in a warm environment, is signficantly dehydrated, orremains in an overwhelmingly hot environment for an extended time. Hyperthermia can also be a side effect of taking illicit substances such as amphetamines and MDMA. A person with hyperthermia may demonstrate confusion, deliriousness, or loss of consciousness, nausea, vomiting, rapid breathing, and will have lost the ability to sweat. This dysregulation of body temperature, if left untreated, can result in organ failure and death.

People can prevent problems with thermoregulation through various methods.

• Practice good hygiene to prevent the spread of bacteria and viruses that can result in fever.
• To prevent hypothermia, dress warm enough for colder temperatures; cover the head and hands, and wear waterproof clothing if applicable.
• To prevent hyperthermia, ensure adequate hydration, whether active or sedentary, in hot conditions. Wear loose-fitting clothing, protect skin from the sun, and refrain from activity during the hottest parts of the day. Take extra precautions if you are on medications that cause dehydration or overheating.