Subclinical hypothyroidism, also called mild thyroid failure or borderline hypothyroidism is diagnosed when thyroid hormone levels are within normal reference range but TSH is mildly elevated.
While this condition affects between 4% and 10% of the population it is more common in women than men and its prevalence increases with age. Between 7% and 26% of the elderly have borderline hypothyroidism.
Studies show that thyroid antibodies can be detected in 80% of patients with borderline hypothyroidism and autoimmune thyroid disease or Hashimoto’s is the most common cause of elevated TSH. The majority of patients with subclinical hypothyroidism have TSH lower than 10 mIU/L.
Other causes of borderline hypothyroidism include a mild thyroid failure due to thyroid surgery, previous radioiodine therapy and external radiation therapy as well as temporary subclinical hypothyroidism after episodes of postpartum, silent and subacute thyroiditis.
The importance and therapy for people with TSH lower than 10 mIU/L and normal T4 are a part of a continued debate and controversy in conventional medicine. Some studies argue for routine and some for selective therapy, however in the real life most doctors take the “wait and watch” approach and do not prescribe any treatment.
8 Benefits of Borderline Hypothyroidism Treatment
Many research studies have pointed to some adverse effects of subclinical hypothyroidism and benefits of thyroid drug therapy:
1. Thyroid medication can slow down or stop progression to hypothyroidism in Hashimoto’s patients in the early stages of disease even if lab tests are normal.
Patients with borderline hypothyroidism have a high rate of progression to clinically overt hypothyroidism. However, it is different for each person and some people do not show progression and up to 10% of people with elevated levels of thyroid antibodies experience a spontaneous remission. A TSH level greater than 10 mIU/L predicts a higher rate of progression, and a level of less than 6 mIU/L predicts a lower likelihood of progression to hypothyroidism.
Some research studies showed that prescribing a low dose of thyroid medication can delay or even prevent the progression of Hashimoto’s to hypothyroidism, reduce inflammation and stop the autoimmune attack on the thyroid.
2. Thyroid medication can help to decrease levels of thyroid antibodies to some degree.
Many people with Hashimoto’s disease don’t have any symptoms initially and are not getting diagnosed until they have hypothyroidism. However, nearly 30% of patients with borderline hypothyroidism may have symptoms that suggest that they are deficient in thyroid hormones.
Increased odds for autoimmune thyroid disease are associated with positivity to TPO or Tb thyroid antibodies during the 2–7 years preceding the hypothyroidism diagnosis. During this time elevated thyroid antibodies are often the only sign that a person has Hashimoto’s disease.
Some research studies showed that prescribing a low dose of thyroid medication can to some degree lower high levels of thyroid antibodies.
3. Thyroid medication can to some extent help to shrink the goiter.
Enlargement of the thyroid gland often accompanies or appears even before hypothyroidism is diagnosed. Thyroid medication can help to stop the growth of the thyroid and shrink the goiter.
4. People on thyroid medication can improve hypothyroid symptoms and overall well-being.
Many studies conducted on patients with TSH in a range from 3 to 32 mIU/L, showed improved symptoms and memory in a quarter of patients.
5. Thyroid drugs can help to lower cholesterol levels and improve other cardiac risk factors.
Several studies showed an association of subclinical hypothyroidism with increased risk of heart disease, arteries plaque building and heart attack and confirmed reduction of LDL cholesterol and improvement in the lipid profile with thyroid drug therapy. Thyroid related high cholesterol levels are resistant to the cholesterol medication, however respond very well to the normalizing of the thyroid function and TSH levels.
6. Improvement of muscle and nerve pain
Neuromuscular symptoms and dysfunction are very common in patients with borderline hypothyroidism and can be reversed by thyroid drug treatment and optimizing T3 levels.
7. Improvement of thyroid related depression, bipolar disorder and mental function.
Mild thyroid failure can aggravate bipolar disorder and depression that are associated with higher than normal TSH and T3 thyroid hormone in the lower normal range and show improvement after thyroid therapy. It is reasonable to have a low threshold for TSH levels for the borderline hypothyroidism treatment in patients with depression, bipolar disorder and mental dysfunction.
8. Thyroid drugs have positive effects on fetus development during pregnancy and treatment of infertility and un-ovulation.
Different normal TSH values are proposed for pregnancy because subclinical hypothyroidism and thyroid autoimmunity poses many risks for the health of mother and unborn baby. The normal range of TSH levels in the first trimester of pregnancy is 0.03 to 2.3 mIU/L. The upper limit of the normal TSH is 3.5 mIU/L in both the second and third trimesters of pregnancy that suggests that borderline hypothyroidism has to be treated.
When Borderline Hypothyroidism Should Be Treated
In conventional medicine treatment of borderline hypothyroidism depends only on the TSH levels, however this approach is not optimal for many thyroid patients and borderline hypothyroidism should be treated in most if not all cases.
Elderly patients and pregnant women in particular can benefit from an early subclinical hypothyroidism treatment to avoid potential consequences of untreated thyroid hormone deficiency.
The decision for thyroid drug therapy for people with TSH levels between 5.0 and 10.0 mIU/L but normal T4 should be individualized and can be especially recommended for the following groups:
- Pregnant women and women who are trying to get pregnant
- Patients with goiter
- People with hypothyroid symptoms
- Teenage girls with a delay of menstrual cycles
- Persistent and gradual increase of TSH
- Depression and bipolar disorder
- Infertility and un-ovulation
- Presence of thyroid antibodies and indication for Hashimoto’s disease
- High cholesterol
- Elderly people especially those who are at an increased risk for the development of atherosclerosis
According to current hypothyroidism treatment guidelines, all patients with subclinical hypothyroidism and TSH level above 10 mIU/L should be treated with thyroid drugs even if the free T4 is within normal laboratory range. The strongest arguments for thyroid drug therapy when TSH is lower than 10 are:
- High risk of progression to full-blown hypothyroidism
- Possible improvement of quality of life
- The fact that subclinical hypothyroidism is a cardiovascular risk factor
However, people with Hashimoto’s disease shouldn’t rely on thyroid medication alone. Most triggers of thyroid autoimmunity are dietary and without addressing your diet and lifestyle modifications that aim to reduce toxicity in your life thyroid drugs have only limited effect.
Hashimoto’s disease is an autoimmune condition when the problem is not with the thyroid gland but with the immune system. New research shows that in addition to genetic and environmental factors leaky gut plays the key role in the initiation of autoimmunity and the increase of thyroid antibodies.
People with subclinical hypothyroidism and elevated thyroid antibodies who start with dietary changes and healing of leaky gut early have the highest chances to stop autoimmune attack on their thyroid completely and go into a non-medicated remission.
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3. Subclinical Hypothyroidism Is Mild Thyroid Failure and Should be Treated, McDermott and Ridgway 86 (10): 4585
4. Effects of Prophylactic Thyroid Hormone Replacement in Euthyroid Hashimoto’s Thyroiditis. Endocrine Journal 2005; 52(3):337-343
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