Sub clinical hypothyroidism

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Subclinical hypothyroidism characteristically presents with elevated thyroid-stimulating hormone (TSH) and normal thyroxine (T4) levels.Various studies have reported the incidence of subclinical hypothyroidism to be 3-15% depending on the population studied. The prevalence of this disorder is bound to increase due to the increased availability of thyroid function testing. Although TSH levels vary widely in the population, intraindividual variation is minimal; this is secondary to a unique individual setpoint in the hypothalamic-pituitary axis. Subclinical hypothyroidism correlates with an increased risk of fatal and non-fatal coronary artery disease (CAD) events, congestive heart failure and fatal stroke.


If your hormone levels are only mildly abnormal, you may have no obvious symptoms. If you do experience symptoms, they could be vague or might mimic other health issues. As in full-on hypothyroidism, symptoms you may experience include:

Depression or other mood issues


Weight gain

Feeling of being cold no matter how warmly you’re dressed

Gut issues, like constipation

An enlarged thyroid gland, or goiter, which may appear as a lump or swelling at the front of the neck


The causes of subclinical hypothyroidism are the same as those of (overt) hypothyroidism and include chronic lymphocytic (Hashimoto's) thyroiditis, partial thyroidectomy, radioactive iodine therapy, and damage to the thyroid from radiation treatment.

Risk factors

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

Gender. A study published in the journal Endocrinology and MetabolismTrusted Source 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 tends to rise as you age, making subclinical hypothyroidism more prevalent in older adults.

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 an iodine deficiency.

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Heart disease

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

high cholesterol

In a 2005 studyTrusted Source looking at older men and women, those with a blood 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

During pregnancy, a blood TSH level is considered 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 The BMJTrusted Source 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 miscarriage than their counterparts who weren’t treated.

Interestingly, though, women with a TSH level between 2.5 and 4 mIU/L didn’t see any reduced risk of pregnancy loss between those treated and those untreated if they had negative thyroid antibodies.


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.