Hypothyroidism happens when the thyroid gland doesn't make enough thyroid hormone. This condition also is called underactive thyroid. Hypothyroidism may not cause noticeable symptoms in its early stages. Over time, hypothyroidism that isn't treated can lead to other health problems, such as high cholesterol and heart problems.
At first, you may barely notice the symptoms of hypothyroidism, such as fatigue and weight gain. Or you may think they are just part of getting older. But as your metabolism continues to slow, you may develop more-obvious problems.
Anyone can get hypothyroidism, including infants. Most babies born without a thyroid gland or with a gland that doesn't work correctly don't have symptoms right away. But if hypothyroidism isn't diagnosed and treated, symptoms start to appear. They may include:
If you're taking thyroid hormone medicine for hypothyroidism, follow your health care provider's advice on how often you need medical appointments. At first, you may need regular appointments to make sure you're receiving the right dose of medicine. Over time, you may need checkups so that your health care provider can monitor your condition and medicine.
Infants with hypothyroidism present at birth that goes untreated are at risk of serious physical and mental development problems. But if the condition is diagnosed within the first few months of life, the chances of typical development are excellent.
Less often, hypothyroidism is caused by too much or too little iodine in the diet or by disorders of the pituitary gland or hypothalamus.1 Iodine deficiency, however, is extremely rare in the United States.
When surgeons remove part of the thyroid, the remaining part may produce normal amounts of thyroid hormone. But some people who have this surgery may develop hypothyroidism. Removing the entire thyroid always results in hypothyroidism.
Radioactive iodine, a common treatment for hyperthyroidism, gradually destroys thyroid cells. If you receive radioactive iodine treatment, you probably will eventually develop hypothyroidism. Doctors also treat people who have head or neck cancers with external radiation therapy, which can also damage the thyroid if it is included in the treatment.
Your hypothyroidism most likely can be completely controlled with thyroid hormone medicine, as long as you take the recommended dose as instructed. Never stop taking your medicine without talking with your doctor first. Taking too much thyroid hormone medicine can cause serious problems, such as atrial fibrillation or osteoporosis.1
You can view a filtered list of clinical studies on hypothyroidism that are open and recruiting at www.ClinicalTrials.gov. You can expand or narrow the list to include clinical studies from industry, universities, and individuals; however, the National Institutes of Health does not review these studies and cannot ensure they are safe. Always talk with your health care provider before you participate in a clinical study.
The difference between hypothyroidism and hyperthyroidism is quantity. In hypothyroidism, the thyroid makes very little thyroid hormone. On the flip side, someone with hyperthyroidism has a thyroid that makes too much thyroid hormone. Hyperthyroidism involves higher levels of thyroid hormones, which makes your metabolism speed up. If you have hypothyroidism, your metabolism slows down.
Many things are the opposite between these two conditions. If you have hypothyroidism, you may have a difficult time dealing with the cold. If you have hyperthyroidism, you may not handle the heat. They are opposite extremes of thyroid function. Ideally, you should be in the middle. Treatments for both of these conditions work to get your thyroid function as close to that middle ground as possible.
In some cases, there can be a connection between untreated hypothyroidism and erectile dysfunction. When your hypothyroidism is caused by an issue with the pituitary gland, you can also have low testosterone levels. Treating hypothyroidism can often help with erectile dysfunction if it was directly caused by the hormone imbalance.
If your hypothyroidism is not treated, you could gain weight. Once you are treating the condition, the weight should start to lower. However, you will still need to watch your calories and exercise to lose weight. Talk to your healthcare provider about weight loss and ways to develop a diet that works for you.
In most cases, hypothyroidism is treated by replacing the amount of hormone that your thyroid is no longer making. This is typically done with a medication. One medication that is commonly used is called levothyroxine. Taken orally, this medication increases the amount of thyroid hormone your body produces, evening out your levels.
Hypothyroidism cannot be prevented. The best way to prevent developing a serious form of the condition or having the symptoms impact your life in a serious way is to watch for signs of hypothyroidism. If you experience any of the symptoms of hypothyroidism, the best thing to do is talk to your healthcare provider. Hypothyroidism is very manageable if you catch it early and begin treatment.
In some mild cases, you may not have symptoms of hypothyroidism or the symptoms may fade over time. In other cases, the symptoms of hypothyroidism will go away shortly after you start treatment. For those with particularly low levels of thyroid hormones, hypothyroidism is a life-long condition that will need to be managed with medication on a regular schedule.
The most common cause of hypothyroidism is an autoimmune disorder. This means your immune system starts to attack itself. It makes antibodies against the thyroid gland. Another cause may be treatment for an overactive thyroid gland. That may include radioactive iodine therapy or surgery.
Abnormalities in thyroid function are common endocrine disorders that affect 5-10 % of the general population, with hypothyroidism occurring more frequently than hyperthyroidism. Clinical symptoms and signs are often nonspecific, particularly in hypothyroidism. Muscular symptoms (stiffness, myalgias, cramps, easy fatigability) are mentioned by the majority of patients with frank hypothyroidism. Often underestimated is the fact that muscle symptoms may represent the predominant or the only clinical manifestation of hypothyroidism, raising the issue of a differential diagnosis with other causes of myopathy, which sometimes can be difficult. Elevated serum creatine kinase, which not necessarily correlates with the severity of the myopathic symptoms, is certainly suggestive of muscle impairment, though it does not explain the cause. Rare muscular manifestations, associated with hypothyroidism, are rhabdomyolysis, acute compartment syndrome, Hoffman's syndrome and Kocher-Debré-Sémélaigne syndrome. Though the pathogenesis of hypothyroid myopathy is not entirely known, proposed mechanisms include altered glycogenolytic and oxidative metabolism, altered expression of contractile proteins, and neuro-mediated damage. Correlation studies of haplotype, muscle gene expression and protein characterization, could help understanding the pathophysiological mechanisms of this myopathic presentation of hypothyroidism.
Thyroid gland hormone production is directly stimulated by TSH, which is synthesized and secreted in the anterior pituitary under stimulation of thyrotropin- releasing hormone produced in the hypothalamus. In patients with an intact hypothalamic- pituitary- thyroid axis, a negative feedback regulatory mechanism controls thyroid gland metabolism. The pituitary serves as a biosensor of thyroid hormone levels and regulates TSH levels according to the feedback of free-thyroxine (FT4) and free-triiodothyronine (FT3) levels. Decreases in thyroid hormone production stimulate more TSH secretion. The control system has a relatively slow response time and during periods of non-equilibrium, as occurs in the beginning of hypothyroidism, it is possible to find some discordance between the plasma thyroid hormone concentrations and the levels of TSH.
TSH measurement is considered to be the main test for detecting thyroid disease, specifically overt and subclinical hypothyroidism, for three main reasons. Firstly, there is an inverse log-linear relationship between the concentrations of TSH and FT4. Consequently, small linear reductions in FT4 concentrations are associated with an exponential increase in TSH concentrations. Secondly, most cases of hypothyroidism in clinical practice are due to primary disease of the thyroid gland. Thirdly, immunometric assays for TSH present greater than 99% sensitivity and specificity.4,5
The second step in the screening of thyroid disorders is to determine the FT4 level. FT4 measurement is highly cost-effective compared to previously used measurements of total T4 or triiodothyronine. The combined measurements of TSH and FT4 can detect two types of hypothyroidism: overt and subclinical.
For a physician to correctly interpret a high TSH level in terms of a hypothyroidism diagnosis, the positive and negative predictive values must be known; these depend on the prevalence of the disease in the general population. As a general rule, higher hypothyroidism prevalence in a population sample indicates a higher positive predictive value of an increased TSH level for hypothyroidism diagnosis. So, in a population with a high prevalence of thyroid disease, the finding of an isolated increased TSH value should be sufficient to confirm the diagnosis.
It is impossible to confirm a diagnosis of hypothyroidism based on clinical symptoms alone, without TSH and FT4 determinations. Due to the increased prevalence according to age and the impossibility of ruling out the diagnosis without laboratory measurements, several guidelines recommend routinely screening for thyroid diseases after a certain age.30 The American Thyroid Association recommends screening both women and men at 35 years of age, and every 5 years thereafter.31 Also assertively in favor of screening, The American Association of Clinical Endocrinologists recommends screening in older patients, especially for women,32 and the American College of Pathologists recommends evaluations for women aged over 50 years with one or more general symptoms that could be caused by thyroid disease.33 The American Academy of Family Physicians recommends screening for patients over 60 years old, independent of gender,34 and the American College of Physicians recommends high-risk strategy for people aged over 50 years with nonspecific complaints.17,18 Among organizations that encourage screening, there is no agreement regarding the guidelines for age and sex. 041b061a72