Cytokines and Inflammation: Balance Required

Inflammation is bad, right? Chronic inflammation has been implicated in cardiovascular disease, type 2 diabetes, non-alcoholic fatty liver disease, cancer, autoimmune diseases, Alzheimer’s disease, other neurodegenerative disorders and more. Ad campaigns for new anti-inflammatory drugs are everywhere, and the best-selling over the counter pain relievers, taken by millions of people, work by suppressing inflammation. It is easy to get the impression that inflammation is always detrimental to health. But, without inflammation, all injuries would be permanent and our defenses against bacterial and viral invaders would be feeble. The inflammatory process is vital to life, the necessary first step in healing and in the body’s defense against infection.  But there is a dark side to this finely tuned system.  Inflammation can become chronic, outlasting the need for defense and repair, and damaging normal tissues in the process.

How inflammation works

Inflammation begins the when cells send out signals that they have been injured, by thermal or physical forces, or attacked, by organisms like bacteria or viruses. The language of this cellular communication is chemical, involving messenger molecules called cytokines (cyto meaning cell and kine, from kinos, meaning movement).  Cytokines attract of white blood cells to the area of injury, and they open pores in nearby tiny blood vessels to let in this defensive army, along with variety of specialized proteins that begin the job of healing.  Inflammation is the word used for the changes that occur in tissues as a result of the orderly events that ensue. With successful healing, signs of inflammation subside, and cellular cytokine production returns to the baseline level necessary for routine cellular maintenance and regeneration.

The normal course of healing inflammation

The cardinal signs of inflammation are redness, heat, swelling and pain. Redness, heat and swelling come from the increase in blood flow and permeability of the blood vessels. Pain is the result of cytokine stimulation of tiny nerve endings, and serves the purpose of limiting movement to limit further damage.  Some cytokine signals reach the temperature control centers in the brain, raising the body temperature to levels invading organisms tolerate poorly. Specialized immune cells immobilize and kill viruses and bacteria and cleanup cells called macrophages clear the debris. Gradually, dead and dying cells are walled off and disposed of. Rebuilding begins, taking advantage of scaffolding produced by the proteins which have leaked from the blood and caused clots to from. You see this process every time scab forms on a cut and later shrinks and peels away to reveal new skin cells beneath.

Maladaptive inflammation

But sometimes the inflammatory system does not gear back down, resulting in tissue damage rather than repair. This control failure may be rapid and catastrophic, the so-called cytokine storm, a term which has become familiar during the 2020 SARS-COV19 pandemic. It describes the damaging effects of an overreaction of the inflammatory response triggered by the immune system during infection or severe trauma. Oncoming cytokine storm cannot be predicted based on routine clinical parameters or tests, but researchers are beginning to tease out more sophisticated chemical markers of inflammation which correlate with more severe disease.

Maladaptive inflammation can also be slow and chronic, with progressive tissue damage like that which occurs in rheumatoid arthritis. The causes of such chronic inflammatory responses are legion and many don’t have obvious relationships to the normal inflammatory pathways. They include obesity, inactivity, toxic chemicals in food and the environment (xenobiotics), poor sleep, chronic infections and antibiotics that alter the normal bowel bacterial populations. Chronic inflammation is also a result of autoimmune responses to the body’s own tissues – cross reactions between immune responses to external agents and to the body’s cells, particularly in skin or joints and other organs like the thyroid gland. No one understands exactly why these self attacks begin to occur but autoimmunity is on the rise in all age groups.

Intertwined systems

The wide ranging influences on the inflammatory system reveals the deep connections between the body’s different physiologic systems. Disruption in one system influences production of chemical signalers in another. For instance, stress and lack of sleep suppress normal defenses against infections. External factors as simple as poor mechanical care of teeth allow chronic gum infections to take hold. Smoking and air pollution irritate the lungs. Lack of exercise changes the way blood flows though arteries, setting them up for damage and chronic inflammatory repair processes. And chronic use of anti-inflammatory drugs for aches and pains alters the finely tuned balance of cytokine signaling throughout the body. 

As we age, chronic inflammatory markers – measurements of some select cytokines like C-reactive protein – tend to rise. Attention to diet, exercise, sleep, dental care and stress management are within your control and help suppress inflammatory marker levels. Removal of allergens and irritating chemical triggers like smoke from the environment helps, as does attention to areas of the body that are sites of chronic infection, like teeth and skin.  

Pharmaceutical interventions are common ways of suppressing chronic inflammation. The NSAIDS, non-steroidal anti-inflammatory drugs like Advil, block cytokines called prostaglandins. Most recently, drugs-called biologicals target individual cytokines by blocking them with antibodies. The new biological drugs provide significant relief to people who suffer from autoimmune problems, but they can also impair the primary functions of defense and repair. Caution is required and risk-benefit calculations are necessary, because opportunistic infections – ones that the body normally handles well – can take hold and thrive. The body’s innate cancer surveillance system, which finds abnormal cells and induces their death before they become malignant, can also become less functional.  

Maintaining the Balance 

Cytokines and the inflammation they cause are part of an enormously complex, finely balanced cellular maintenance and body defense system. Small disruptions in the balance over time, such as happens with chronic use of anti-inflammatory drugs for treatment of pain, or chronic stimulation from infection, can show up in odd and seemingly unrelated ways, like an increased rate of heart attacks and strokes in chronic NSAID users and development of liver cancer in hepatitis sufferers. In an imperfect world, perfect balance is hard to maintain, but the inflammatory response system is far more often good than bad.    

Blood Clotting…and Not Clotting

    Over a gallon of blood circles your body every 45 seconds, under pressure, in a network of arteries, veins and capillaries.  Any leaks in the system must be plugged and repaired. Some ruptures are emergencies requiring outside help, but most are fixed handily by a well calibrated system of physical and chemical reactions in your body.  You watch this process every time you cut yourself shaving or slicing tomatoes, but it also happens microscopically, all over your body, when blood vessels are damaged internally by trauma or infection or chronic degenerative changes in the walls of arteries.  

How clotting happens 

Hemostasis, the first step in controlling bleeding, involves mechanical measures like pressure, cautery or stitches to stop blood flow from damaged blood vessels. Hemostasis alone is ineffective and must to be accompanied by blood clotting, a process triggered by blood platelets, which are tiny little disc shaped cell fragments that accumulate at the site of blood vessel injury. About a trillion platelets circulate in the blood, speeding by over 10,000 square feet endothelial cells that line the inside walls of blood vessels. When damage exposes collagen and other proteins in the endothelial cells and surrounding tissues, platelets gather to plug the defect, while secreting chemicals that draw white blood cells to the scene. An orderly sequence of chemical reactions, known as the clotting cascade, then produces in a stringy mass of sticky protein called fibrin, which fills the gaps between the platelets. Over the next few days to weeks, as healing proceeds, the clot gradually dissolves and disappears in a process called lysis. Your scab falls off to reveal new skin underneath.

Balance between clotting and not clotting

Blood also must not clot to carry out its normal function of transporting oxygen and carbon dioxide and nutrients and waste. If blood clots occur inside blood vessels, they block blood flow and cause damage in surrounding tissues. Health problems like strokes and heart attacks, and clots in the heart, lungs and leg veins occur because local conditions like inflammation and slow blood flow trigger the clotting process. For example, when atrial fibrillation causes failure of atrial pumping, blood pools in the recesses of the upper chambers of the heart and clots may form.  Slow and turbulent blood flow in arteries narrowed by inflamed cholesterol plaques sets off the clotting process. Immobilization, bed rest or even prolonged sitting can promote clot formation in the leg veins.

Manipulation of the clotting system

Health problems like these, as well as the need to hasten clotting in some medical situations, drive attempts to manipulate the clotting system. Infusions of platelets and other blood products correct bleeding in the operating room and in medical conditions that lead to poor clotting, but, more commonly, medical problems require suppressing the blood clotting response. Most people are familiar with anti-clotting drugs, called “anticoagulants,” that interfere with one or more of the chemical processes in the clotting cascade. They are used for common heart problems like atrial fibrillation, leg vein clots and after heart valve replacements to prevent the foreign valve materials from triggering clotting. Most people are also familiar with “antiplatelet” drugs like aspirin used to help prevent heart attacks and strokes by interfering with the ability of platelets to start the clotting process. 

Pharmacological aid in breaking down clots 

A third type of intervention employing “thrombolytic” drugs aims to dissolve clots that have already formed.Thrombolytic drugs are used in hospitals, in the acute setting of clots that have caused heart attacks and strokes. When injected into arteries, they dissolve clot and restore blood flow though the problem area of the blood vessel that triggered the clotting process, or through an artery in the brain that has been suddenly blocked by a clot that traveled there from the heart.

Blood “thinners”

 Anticoagulant drugs are often incorrectly called blood thinners, but they do not change the thickness of blood. They block reactions in the clotting cascade. Heparin, when injected intravenously, causes the most direct and immediate interference, so doctors opt for this choice (or other similar drugs if a patient is allergic to heparin) when stopping clot formation is urgent. The insertion of an artificial heart valve, which will trigger clot formation on its surface, the presence of leg clots which may break off and travel to the lungs, or the onset of atrial fibrillation call for prompt blocking of clot formation, while the transition is made to oral anticoagulant drugs.

Oral anticoagulant drugs take a few days to slow the speed of blood clotting.  Of the oral drugs available for blocking clotting, coumadin is the oldest and most frequently used because its anticoagulant effects can be stopped quickly, if necessary. The ability to reverse anti-clotting effects is important if the anticoagulated patient develops a bleeding problem or is at risk of falling or other injury. Coumadin’s effects are reversed by intravenous injection of Vitamin K. People taking coumadin must have their blood checked regularly to monitor the rate at which the blood clots, and adjust doses accordingly. Other newer oral anticoagulants are popular because they do not require testing, but are more expensive and their effects cannot be reversed as quickly.  Intramuscular drugs are available for home use, usually when anticoagulation is a temporary treatment.

Drugs that make platelets less sticky

Antiplatelet drugs like aspirin and persantin are often prescribed to prevent clot formation in the coronary arteries, though the evidence about their benefits is mixed.  Far more common, however, is the unsuspected antiplatelet effect encountered by people using many over the counter products, particularly non-steroidal anti-inflammatory drugs (NSAIDS) used for pain, and some supplements like fish oil. Aspirin and NSAIDS are implicated in stomach bleeding episodes and in heavy menstrual bleeding.

 In addition to its role in repairing leaks and keeping blood running freely through the vast network of blood vessels in the body, the complex chemistry of the blood clotting system is revealing itself to be intricately involved in other aspects healing and in immune-mediated inflammatory states (such as COVID-19). The attempt to immunize against the SARS-COV2 virus has also focused attention on blood clotting, with the antigen chosen to stimulate antibody formation triggering serious adverse events involving both clotting and bleeding, as well as unsuspected clot formation in very small blood vessels. Knowledge is accumulating rapidly and, as it does, expect to see blood platelets revealed as much more than pieces of cells used to plug holes and the clotting system more closely related to the inflammatory system.  

Thyroid Failure:Hashimoto’s Disease

When I was a resident in medical training a woman arrived in the emergency room in a coma. She had been living alone and, according to neighbors, sitting in a chair in her apartment for weeks. Her clinical state was like one of hibernation, with very low pulse, blood pressure and temperature. Her hair was like thin and brittle, her skin scaly and dry, her face puffy and her legs thickened by a waxy swelling called myxedema. She was in the final stages of thyroid gland failure, myxedema coma. Early in the course of her illness, when symptoms were probably mild and ill-defined, no one had realized she was “hypothyroid.” Later, when thyroid hormone levels had fallen to dangerous lows, she was too slow mentally and physically to seek help. By the time she arrived in the ER she was on the brink of death from Hashimoto’s disease, an autoimmune inflammation of the thyroid gland, or thyroiditis. Hashimoto’s disease was the first recognized disease caused by the immune system attacking some part of the body, and is the most common cause of thyroid gland failure in the USA.

Hashimoto’s disease affects at least one in every 1000 people in the US, women more frequently than men.  Though the thyroid disease was first described in 1912, and is now known to be caused by the production of antibodies against thyroid hormone producing enzymes and proteins, there is still no known way to prevent it. The only risk factor is a family history of a similar problem. Some environmental factors such as high iodine intake and viral infections may play a role in triggering the process in genetically susceptible individuals. In Hashimoto’s disease, the antibodies gradually destroy the gland’s hormone producing follicles. Most often, the thyroid gradually and irregularly enlarges as the follicles are replaced by inflammatory tissue. While the bumpy neck bulge created is similar to a goiter, the latter is smoother and more regular in shape and a sign of an overworking but non-inflamed thyroid gland which is getting insufficient dietary iodine.

In Hashimoto’s disease, subtle physical symptoms often precede the development of an enlarged thyroid gland. Since thyroid hormone facilitates all metabolism and energy production in every part of the body, inadequate amounts of the hormone cause a host of vague symptoms which are often excused as simply the byproduct of life style inadequacies such as too little sleep, poor diet, lack of exercise and stress. The symptoms include fatigue, weight gain, depression and anxiety, inability to stay warm, joint and muscle aches and pains, constipation, slow pulse, coarse and thinning hair, puffiness, irregular menstrual periods, and inability to conceive. In some people, gland enlargement never occurs. And though the underlying problem is inflammatory, the thyroid gland is not tender.

Because of the vague nature of the symptoms that bring a patient with Hashimoto’s thyroiditis to the doctor, because the thyroid gland may not be enlarged and because the screening blood test for total thyroid hormone level may fall within a normal range, many other diagnoses are often entertained before the correct one is made. These include depression, anxiety, chronic fatigue syndrome and subclinical infection. In addition, because hypothyroidism drives cholesterol and weight up, attention gets diverted to heart disease and other components of the metabolic syndrome.

But once suspicion of Hashimoto’s has been raised, the problem is easily identified by blood tests for antibodies to an enzyme called thyroid peroxidase and to a thyroid hormone binding protein called thyroglobulin and a test for a pituitary gland hormone called TSH, or thyroid stimulating hormone.  TSH rises as thyroid function fails and the pituitary gland attempts to stimulate it to keep producing thyroid hormone.

Some patients need thyroid scans and biopsies of any suspicious gland areas to rule out the very rare possibility that a lump in the gland is cancerous. A general medical evaluation is also helpful since low thyroid hormone can accelerate cardiovascular disease and since the autoimmune dysfunction underlying Hashimoto sometimes occurs in association with other autoimmune disorders such as celiac disease, Type 1 diabetes, adrenal gland insufficiency, autoimmune gastritis with Vitamin B12 deficiency, rheumatoid arthritis, lupus, and some clotting disorders that may cause either bruising or clot formation in blood vessels.

If other autoimmune problems are not found, the therapy for Hashimoto’s thyroiditis is as easy as taking one pill a day, usually a synthetic thyroid hormone called levothyroxine. Prior to the development of synthetic thyroid hormone, a desiccated powder made from pig thyroid glands was the only treatment available and it is still preferred by a significant number of patients. A controlled study done in 2013 to determine whether there was any scientific evidence for treatment preference showed that both synthetic thyroid hormone and desiccated thyroid hormone are equally effective in raising thyroid hormone levels and returning TSH levels to normal, but that desiccated thyroid hormone resulted in slightly greater weight loss.

Our myxedema coma patient survived, though her management was difficult because of the severity of her hypothyroidism. Under the autoimmune attack of Hashimoto’s thyroiditis, the thyroid gland is a victim of a very slow war of attrition as more and more of its structure is replaced by inflammatory cells and scar tissue.  The fall-off in hormone production is slow, and the body adapts to lower and lower levels of thyroid hormone until all systems finally begin shutting down. At that point, re-introducing high levels of thyroid hormone can be dangerous to heart function. The correction must occur gradually, as the decline did, underscoring the importance of detecting thyroid gland failure early, before it takes such a metabolic toll. Even when discovered early, the establishment of appropriate hormone dose and the reversal of symptoms may take some time and patience. The hormone must be taken for the rest of a long and otherwise normal life.


Thyroid Ups and Downs

Early in her husband’s presidency, first lady Barbara Bush began to lose weight. Her eyes became, in her own words “horrible and puffy” looking.” She had developed an autoimmune thyroid gland problem called Graves’ Disease. A few months later, the Bush‘s dog Millie came down with another autoimmune disease – lupus. The next spring, the president became ill with weight loss and a rapid, irregular heartbeat. Like Barbara he had Graves’ disease. Conspiracy theorists blamed Saddam Hussein for this outbreak of autoimmune disease in the White House, but thyroid experts saw nothing but coincidence. They admit, though, that they do not know what triggers antibody attacks against the thyroid gland, the most common cause of thyroid disease.

The many and varied symptoms of thyroid disease
Symptoms of thyroid disease most often involve effects of the hormones the gland makes. Thyroid hormone stokes the fire of metabolism, setting the rate of energy usage in every cell of the body and determining the basal metabolic rate (number of calories burned at complete rest).
Too much thyroid hormone causes hyperthyroidism; too little creates hypothyroidism. Extreme cases of either problem are easy to diagnose, but milder excess or deficiency states are much trickier and more common (an estimated 7-10% of adults have thyroid abnormalities). Hyperthyroid patients lose weight, become intolerant of warm environments and sweat profusely. Hair becomes thin and fine. The heart beats too fast and blood pressure rises, while muscles feel weak and hands shake. Sleep becomes elusive. On the hypothyroid end of the spectrum, lack of thyroid hormone banks the metabolic fires and drops the heat. Patients feel cold and become constipated. Incoming energy gets stored as fat; weight and cholesterol levels climb. Lethargy encroaches on daytime hours, and ambition and mental quickness decline. Both under and overactive glands can be enlarged and even visible as swellings just under the Adam’s apple.

The confirmation of the thyroid gland’s role in symptoms comes from blood tests that measure thyroid hormone levels. Extreme cases are easy to diagnose. Milder cases, with less impressive symptoms and “borderline” blood tests are trickier. Mild symptoms overlap many of life’s normal patterns that are unrelated to thyroid hormone: weight, blood pressure and cholesterol tend to go up with age; sedentary people frequently feel cold and constipated; women at menopause would sometimes like to abolish indoor heating, and physical and mental energy are always subject to lifestyle, happiness, and drug effects. The opinion of an endocrinologist is particularly helpful in interpreting borderline thyroid symptoms and lab values.
Thyroxin or T4 (with four iodine molecules) comes from the thyroid gland. Tri-iodothyronine (T3) comes from T4 when one iodine molecule is split off. Thyroid stimulating hormone (TSH), made in the pituitary gland, is like a thermostat that regulates how much T4 the thyroid gland makes. When T4 is too high, TSH goes down. When T4 is too low, TSH goes up. So hypothyroid patients have high TSH and low T4, and hyperthyroid patients have low TSH and high T4.
Symptoms suggesting hyperthyroidism, combined with high-normal T4 and T3 and low- normal TSH prompt further tests to look directly at the thyroid gland. Thyroid scans employ radioactive iodine and distinguish between glands that overproduce in all areas, ones that have nodules of overproduction, and enlarged glands that no longer make any hormone. Measurement of three different types of anti-thyroid antibodies further narrows the diagnosis.

The problems with the tests
Not all labs use the same ranges of normal values. Some rely on broad TSH ranges found in a random selection of apparently healthy people (0.32 -5.0 µIU/ml). Other labs use a much narrower range (.34-2.5µIU/ml) found in people who have been screened to rule out thyroid disease. So if you see a doctor who uses the first range and your TSH is 4.5, you might be told just to watch your weight, get better sleep, take a little blood pressure medicine and be rechecked in 6 months or a year. A doctor using the second might would give you a prescription for thyroid hormone. Treatment of hypothyroidism in these gray areas might normalize the blood tests without producing any clinically identifiable benefits. Nevertheless, it is wise to follow up on iffy test results because, over time, thyroid conditions may declare themselves further.

Autoimmune thyroid disease
Graves Disease and Hashimoto’s thyroiditis, caused by different types of antibodies, are the most common causes of thyroid problems and tend to run in families. In Graves ’ disease, the antibodies may also attack eye muscles and make them swell, producing the characteristic bulging eyes that Barbara Bush complained about. Graves disease most often begins with a hyperthyroid state that requires treatment to suppress overproduction of thyroid hormone or to obliterate the gland by radiation, producing hypothyroidism that requires treatment; sometimes Graves’ improves on its own but then goes on to hypothyroidism. Hashimoto’s disease most commonly bypasses the clinical hyperthyroid phase altogether and is the most common cause of hypothyroidism.

Iodine deficiency
Lack of dietary iodine once caused many cases of hypothyroidism. The word cretin (slang for dunce, idiot) originated in a mountainous French region where iodine deficient soil and lack of iodine-rich seafood resulted in a high incidence of mental and physical retardation from hypothyroidism in babies. Thyroid hormone and the dietary iodine required to make it are critical for normal growth and development, especially of the brain. In modern societies babies are screened and treated for hypothyroidism, and iodized salt makes this essential element easily available so this once frequent deficiency is much less common.

Oral, synthetic versions of T3 and T4, or “natural” versions made from batches of pig thyroid glands make failing thyroid glands easily treatable. Synthetic versions are easier to regulate than are the natural ones. Finding the proper dose to return the blood tests to the normal range is often much easier than finding the dose and timing of pills that improves symptoms. The latter process is an inexact science that sometimes results in too much hormone effect.
Overactive glands are treated with medicines that shut them down, sometimes with radioactive iodine that kills the glandular cells and sometimes with surgery to remove the entire gland. The latter two treatments always produce hypothyroidism which then requires treatment with replacement hormones.
One study on thyroid disease prevalence estimates that there are 13,000,000 Americans with undiagnosed thyroid problems. Thyroid tests are now part of routine blood work, more problems will be caught and treated earlier, and more will be learned about triggers for autoimmune thyroid problems – eventually putting at least one conspiracy theory to rest.

Notes on less Common Thyroid Conditions

Lumps in the thyroid: These are common and most are benign nodules or cysts; sometimes they produce thyroid hormone and cause hyperthyroidism.

Viral thyroiditis (also known as sub-acute thyroiditis): self-limited illness with several weeks of hyperthyroidism, followed by several weeks of hypothyroidism, and then recovery of normal function.

Thyroid cancer: Uncommon. Rarely produces thyroid hormone so usually the diagnosis results from evaluation of lump in the neck or hoarseness; results from radiation exposure – as once was the practice for treating acne.

Pituitary Gland Tumors: Pituitary failure to produce TSH causes hypothyroidism; very rarely the pituitary overproduces TSH and causes hyperthyroidism.

Dietary Hyperthyroidism: At least one outbreak of hyperthyroidism came from meat contaminated with animal thyroid glands. Another rare cause is sudden, excessive iodine supplementation in a patient with underlying thyroid disease .

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