Underactive thyroid (hypothyroidism) is often overlooked or misdiagnosed and can be the underlying cause of these symptoms. Patients and their doctors often disregard these common signs of thyroid hormone deficiency, mistaking them for normal aging.
Role of the Thyroid
The thyroid is a butterfly-shaped organ located just below the Adam’s apple in the neck. Made up of small sacs, this gland is filled with an iodine-rich protein called thyroglobulin along with the thyroid hormones thyroxine (T4) and small amounts of triiodothyronine (T3). The primary function of these two hormones is to regulate metabolism by controlling the rate at which the body converts oxygen and calories to energy. In fact, the metabolic rate of every cell in the body is regulated by thyroid hormones, primarily T3. In healthy individuals the gland is imperceptible to the touch. A visibly enlarged thyroid gland is referred to as a goiter. Historically, goiter was most frequently caused by a lack of dietary iodine. 8 However, in countries where salt is iodized, goiter of iodine deficiency is rare.
Subclinical hypothyroidism, an often under-diagnosed thyroid disorder, manifests as elevated TSH, normal T4 and normal T3 levels.30 Individuals with subclinical hypothyroidism are at greater risk for developing overt hypothyroidism.31 An August 2010 study reported that 8.3% of women with no history of thyroid disease suffer from subclinical hypothyroidism.32 An article in the American Family Physician in 2005 estimated that about 20% of women over the age of 60 suffer from subclinical hypothyroidism.
Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormones, characterized by a reduction in metabolic rate. The main symptoms of hypothyroidism are fatigue, weakness, increased sensitivity to cold, constipation, unexplained weight gain, dry skin, hair loss or coarse dry hair, muscle cramps and depression. However, most symptoms take years to develop. The slower the metabolism gets, the more obvious the signs and symptoms will become. If hypothyroidism goes untreated, the signs and symptoms could become severe, such as a swollen thyroid gland (goiter), slow thought processes, or dementia.
There is evidence that the standard blood TSH test reference range may cause many cases of hypothyroidism to be missed. Most physicians accept a reference range for TSH between 0.45 and 4.5 mU/L to indicate normal thyroid function. In reality, though, a TSH reading of more than 2.0 may indicate lower-than-optimal thyroid hormone levels.
According to a study reported in Lancet, various TSH levels that fall within normal range are associated with adverse health outcomes.26
- TSH greater than 2.0: increased 20-year risk of hypothyroidism and increased risk of thyroid autoimmune disease
- TSH between 2.0 and 4.0: hypercholesterolemia and cholesterol levels decline in response to T4 therapy
- TSH greater than 4.0: greater risk of heart disease
There is another and separate problem brought on by these overly broad normal ranges for TSH. People already diagnosed and being treated for hypothyroidism are often not taking correct doses of thyroid replacement hormone. A November 2010 study reported that about 37% of people being treated for hypothyroidism were taking incorrect doses, about half too much and another half too little hormone.
Consequences of Hypothyroidism
Gastrointestinal problems: Hypothyroidism is a common cause of constipation. Constipation in hypothyroidism may result from diminished motility of the intestines. In some cases, this can lead to intestinal obstruction or abnormal enlargement of the colon.36 Hypothyroidism is also associated with decreased motility in the esophagus, which causes difficulty swallowing, heartburn, indigestion, nausea, or vomiting. Abdominal discomfort, flatulence, and bloating occur in those with small intestinal bacterial growth secondary to poor digestion.31
Depression and psychiatric disorders: Panic disorders, depression, and changes in cognition are frequently associated with thyroid disorders.37 Hypothyroidism is often misdiagnosed as depression.38 A study published in 2002 suggests that that thyroid function is especially important for bipolar patients: “Our results suggest that nearly three-quarters of patients with bipolar disorder have a thyroid profile that may be suboptimal for antidepressant response.” 39
Cognitive decline: Patients with low thyroid function can suffer from slowed thinking, delayed processing of information, difficulty recalling names, etc.40 Patients with subclinical hypothyroidism show signs of decreased working memory,41 and decreased speed of sensory and cognitive processing.42 An evaluation of thyroid hormones along with TSH may help avoid misdiagnosis as being depressed. 43
Cardiovascular Disease: Hypothyroidism and subclinical hypothyroidism are associated with increased levels of blood cholesterol, increased blood pressure, and increased risk of cardiovascular disease. 44 Even those with subclinical hypothyroidism were almost 3.4 times as likely to develop cardiovascular disease than those with healthy thyroid function.
- High blood pressure: Hypertension is relatively common among patients with hypothyroidism. In a 1983 study, 14.8% of patients with hypothyroidism had high blood pressure, compared with 5.5% of patients with normal thyroid function. “Hypothyroidism has been recognized as a cause of secondary hypertension. Previous studies … have demonstrated elevated blood pressure values. Increased peripheral vascular resistance and low cardiac output has been suggested to be the possible link between hypothyroidism and diastolic hypertension.”
- High cholesterol and atherosclerosis: “Overt hypothyroidism is characterized by hypercholesterolemia and a marked increase in low-density lipoproteins (LDL) and apolipoprotein B” These changes accelerate atherosclerosis, which causes coronary artery disease.43 The risk of heart disease increases proportionally with increasing TSH, even in subclinical hypothyroidism.49 Hypothyroidism that is caused by autoimmune reactions is associated with stiffening of the blood vessels. Thyroid hormone replacement may slow the progression of coronary heart disease by inhibiting the progression of plaques.
- Homocysteine: Treating hypothyroid patients with thyroid hormone replacement might attenuate homocysteine levels, an independent risk factor for cardiovascular disease: “A strong inverse relationship between homocysteine and free thyroid hormones confirms the effect of thyroid hormones on homocysteine metabolism.”
- Elevated C-reactive protein: Overt and subclinical hypothyroidism are both associated with increased levels of low-grade inflammation, as indicated by elevated C-reactive protein (CRP). A 2003 clinic study observed that CRP values increased with progressive thyroid failure and suggested it may count as an additional risk factor for the development of coronary heart disease in hypothyroid patients.
Metabolic Syndrome: In a study of more than 1,500 subjects, researchers found that those with metabolic syndrome had statistically significantly higher TSH levels (meaning lower thyroid hormone output) than healthy control subjects. Subclinical hypothyroidism was also correlated with elevated triglyceride levels and increased blood pressure. Slight increases in TSH may put people at higher risk for metabolic syndrome.
Reproductive system problems: In women, hypothyroidism is associated with menstrual irregularities and infertility. Proper treatment can restore a normal menstrual cycle and improve fertility.
Fatigue and weakness: The well known and common symptoms of hypothyroidism, such as chilliness, weight gain, paresthesia (tingling or crawling sensation in the skin) and cramps are often absent in elderly patients compared with younger patients, fatigue and weakness are common in hypothyroid patients.
Hypothyroidism: What you need to know
- Thyroid diseases occur about five times more frequently in women than in men. As many as 20% of women over 60 years old have subclinical hypothyroidism.
- If untreated, chronic hypothyroidism can result in myxedema coma, a rare, life-threatening condition. Mental dysfunction, stupor, cardiovascular collapse, and coma can develop after the worsening of chronic hypothyroidism as well.
- An autoimmune disease called Hashimoto’s thyroiditis is the most common cause of low thyroid function in the US. The body’s immune system mistakenly attacks the thyroid tissue impairing the ability to make hormones.79 Hypothyroidism caused by Hashimoto’s disease is treated with thyroid hormone replacement agents.
- Hashimoto’s disease usually causes hypothyroidism, but may also trigger hyperthyroid symptoms.
- Hyperthyroidism is usually caused by Graves’ disease, in which antibodies are produced that bind to TSH receptors in the thyroid gland, stimulating excess thyroid hormone production.20
- The distinction between Hashimoto’s thyroiditis and Graves’ disease may not be as important as once thought. In 2009 researchers wrote that, “Hashimoto’s and Graves’ disease are different expressions of a basically similar autoimmune process, and the clinical appearance reflects the spectrum of the immune response in a particular patient.”81 The two diseases can overlap causing both thyroid gland stimulation and destruction simultaneously or in sequence.82 Some clinicians consider the two conditions different presentations of the same disease.83 About 4% of patients with Graves’ disease displayed some symptoms of Hashimoto’s thyroiditis during childhood.
- Pregnant women are especially at risk for hypothyroidism. During pregnancy, the thyroid gland produces more thyroid hormone than when a woman is not pregnant,85 and the gland may increase in size slightly.
- Uncontrolled thyroid dysfunction during pregnancy can lead to preterm birth, mental retardation, and hemorrhage in the postpartum period. 86 It is important to work closely with a physician to monitor thyroid function during pregnancy.
- Tests to diagnose and monitor hypothyroidism include: Thyroid Stimulating Hormone (TSH), Total T4, Total T3, Free T4 (fT4), Free T3 (fT3), Reverse T3 (rT3), Thyroid peroxidase antibody (TPOAb), Thyroglobulin antibody (TgAb)
Conventional treatment almost always begins with synthetic T4 (levothyroxine) preparations like Synthroid® or Levoyxl®. Low doses are usually used at first because a rapid increase in thyroid hormone may result in cardiac damage.
Desiccated Thyroid: Armour thyroid , Nature-throid, and Westhroid are prescription medications that contain desiccated porcine thyroid gland. Natural thyroid extracts have been used since 1892 and were approved by the Food and Drug Administration in 1939. Armour thyroid and most other natural glandular preparations are made to standards approved by the United States Pharmacopoeia.
Armour thyroid is preferred by some clinicians because it may achieve results in patients that fail to respond to levothyroxine alone. Patients with hypothyroidism show greater improvements in mood and brain function if they receive treatment with Armour thyroid rather than Synthroid®.96 One argument favoring natural hormones is that other naturally occurring hormones and chemicals found in these preparations may buffer or enhance the effect of the active hormones.
Absorption of Thyroid hormone Medications: Coffee,97 aluminum antacids,98 ferrous sulfate (iron),99 calcium carbonate,100 soy 101 and possibly grapefruit juice102 can all decrease the absorption of thyroid hormone prescriptions. Most doctors simply advise patients to take thyroid away from any food or medication.
If you have concerns about your thyroid function, call today to schedule an appointment with Dr Carnahan for an complete evaluation and treatment of thyroid dysfunction.
* These statements have not been evaluated by the Food and Drug Administration. The product mentioned in this article are not intended to diagnose, treat, cure, or prevent any disease. The information in this article is not intended to replace any recommendations or relationship with your physician. Please review references sited at end of article for scientific support of any claims made.