What Is Subclinical Hypothyroidism?

什么原因是什么？

The pituitary gland, located at the base of the brain, secretes multiple hormones, including a substance called thyroid-stimulating hormone (TSH).

TSH triggers the thyroid, a butterfly-shaped gland at the front of the neck, to make the hormones T3 and T4. Subclinical hypothyroidism occurs when TSH levels are slightly elevated but T3 and T4 are normal.

Subclinical hypothyroidism and full-blown hypothyroidism share the same causes. These include:

• a family history of autoimmune thyroid disease, such asHashimoto’s thyroiditis（危害甲状腺细胞的自身免疫病症）
• 对甲状腺的损伤（例如，在头部和颈部手术期间除去一些异常的甲状腺组织）
• the use of radioactive iodine therapy, a treatment forhyperthyroidism(a condition when too much thyroid hormone is produced)
• 服用含锂或碘的药物

Who’s at risk?

A variety of things, most of which are outside of your control, increase the chances of developing subclinical hypothyroidism. These include:

• Gender.在期刊上发表的一项研究 Endocrinology and Metabolism showed that women are more likely to develop subclinical hypothyroidism than men. The reasons aren’t entirely clear, but researchers suspect the female hormone estrogen may play a role.
• Age.TSH随着年龄的增长而趋于崛起，使亚临床甲状腺功能减退症在老年人中更普遍。
• Iodine intake.Subclinical hypothyroidism tends to be more prevalent in populations that consume sufficient or excess iodine, a trace mineral essential for proper thyroid function. It can help to be familiar with the signs and symptoms of aniodine deficiency.

Common symptoms

Subclinical hypothyroidism most of the times has no symptoms. This is especially true when TSH levels are only mildly elevated. When symptoms do arise, however, they tend to be vague and general and include:

• 沮丧
• constipation
• fatigue
• goiter(this appears as swelling in the front of the neck due to an enlarged thyroid gland)
• weight gain
• 脱发
• 不容忍冷

值得注意的是，这些症状是非特异性的，这意味着它们可以存在于具有正常甲状腺功能的个体中，与亚临床甲状腺功能亢进无关。

How it’s diagnosed

Subclinical hypothyroidism is diagnosed with ablood test.

A person with a normal functioning thyroid should have a blood TSH reading within the normal reference range, which commonly goes up to4.5 milli-international units per liter (mIU/L)要么 5.0 miu / l .

However, there’s debate underway in the medical community about lowering the highest normal threshold.

People with a TSH level above the normal range, who have normal thyroid gland hormone levels, are considered to have subclinical hypothyroidism.

Because amounts of TSH in the blood can fluctuate, the test may need to be repeated after a few months to see if the TSH level has normalized.

How it’s treated

关于如何 - 甚至if - 对治疗亚临床甲状腺功能减退的人有很多争论。如果TSH水平低于10 mIU / L，这尤其如此。

Because a higher TSH level can start to produce adverse effects on the body, people with a TSH level over 10 mIU/L are generally treated.

According to research from 2009 , evidence is mostly inconclusive that those with TSH levels between 5.1 and 10 mIU/L will benefit from treatment.

In deciding whether or not to treat you, your doctor will take into consideration things like:

• your TSH level
• whether or not you have antithyroid antibodies in your blood and a goiter (both are indications the condition may progress to hypothyroidism)
• your symptoms and how much they’re affecting your life
• your age
• your medical history

When treatment is used,levothyroxine(Levoxyl, Synthroid), a synthetic thyroid hormone taken orally, is often recommended and is generally well tolerated.

Are there complications?

心脏病

The connection between subclinical hypothyroidism and cardiovascular disease is still being debated. Some studies do suggest that elevated TSH levels, when left untreated, may contribute to developing the following:

• high blood pressure
• 高胆固醇

In a 2005 study 看着老男人和女人,那些血TSH level of 7 mIU/L and above were at twice the risk or more for having congestive heart failure compared to those with a normal TSH level. But some other studies didn’t confirm this finding.

Pregnancy loss

在怀孕期间,血TSH水平被认为是elevated when it exceeds 2.5 mIU/L in the first trimester and 3.0 mIU/L in the second and third. Proper thyroid hormone levels are necessary for fetal brain and nervous system development.

Research published in BMJ. found that pregnant women with a TSH level between 4.1 and 10 mIU/L who were subsequently treated were less likely to have a流产than their counterparts who weren’t treated.

然而，有趣的是，在2.5和4 miu / L之间的TSH水平的女性没有看到那些治疗的人之间的妊娠损失的任何风险，如果它们具有负甲状腺抗体，那么如果它们具有负甲状腺抗体。

Assessing the status of antithyroid antibodies is important.

According to a2014 study, women with subclinical hypothyroidism and positive antithyroid peroxidase (TPO) antibodies tend to have the highest risk of adverse pregnancy outcomes, and adverse outcomes happen at a lower TSH level than in women without TPO antibodies.

A2017 systematic reviewfound that the risk of pregnancy complications was apparent in TPO-positive women with a TSH level greater than 2.5 mU/L. This risk wasn’t consistently apparent in TPO-negative women until their TSH level exceeded 5 to 10 mU/L.

Best diet to follow

没有良好的科学证据表明吃或不吃某些食物肯定会有助于从亚临床甲状腺功能亢进症静置或治疗，如果你已经被诊断出来。但是，重要的是an optimal amount of iodine在你的饮食中。

Too little iodine can lead to hypothyroidism. On the other hand, too much may lead to either hypothyroidism or hyperthyroidism. Good sources of iodine include iodized table salt, saltwater fish, dairy products, and eggs.

The National Institutes of Health recommends 每天150微克 for most adults and teenagers. One-quarter teaspoon of iodized salt or 1 cup of low-fat plain yogurt provides about 50 percent of your daily iodine needs.

总而言之，您可以为您的甲状腺功能做的最好的事情是吃均衡，营养丰富的饮食。

What’s the outlook?

由于研究互相冲突，仍有很多关于如何治疗亚临床甲状腺功能减退症的争论。最好的方法是个人。

Talk to your doctor about any symptoms, your medical history, and what your blood tests show.This handy discussion guide can help you get started.研究您的选择，并在一起决定最好的行动方案。