Everything About Subclinical Hyperthyroidism Causes, Treatment, Diagnosis

Overview

Subclinical Hyperthyroidism is a condition characterized by low levels of TSH (thyroid stimulation hormone), with normal T4 and T3 serum concentrations.

The thyroid gland (an endocrine gland located at the base of the neck, and small in size) secretes T4 (thyroxine) and T3 hormones. T4 is considered a chief hormone, which is controlled by the levels of TSH (produced by the pituitary gland) production. However, T3 (triiodothyronine) is a modified version of T4.

Thus, if the pituitary gland spots very little T4, it will produce more TSH, telling the thyroid gland to make more T4. Once the T4 values reach appropriate levels, the pituitary gland identifies that and stops TSH production.

In people who have subclinical hyperthyroidism, their thyroid produces normal values of T3 and T4. However, they have a lesser amount of TSH than normal. This imbalance in hormone levels leads to the condition.

The incidence of subclinical hyperthyroidism in general people is estimated to range from 0.6 to 16%, but it depends on diagnostic criteria.    

Read also What is Subclinical Hypothyroidism and Overt hypothyroidism

Common causes

Subclinical hyperthyroidism can be both external (exogenous) and internal (endogenous) factors. 

Internal causes 

include:

Thyroiditis: refers to a swelling or inflammation of the thyroid that causes either by abnormally low or high levels of thyroid hormones in the blood.

Thyroid adenoma: a noncancerous lump (benign tumor) of the thyroid gland. 
Graves' disease: is an autoimmune disease that involves the immune system hitting healthy tissues of the thyroid gland for unknown reasons. It can lead to the overactivity of the thyroid gland.

Multinodular goiter: goiter is an expanded form of the thyroid gland, and a multinodular goiter is an enlarged thyroid consisting of multiple nodules, or lumps. 

External cause 

includes

• Unintended TSH suppression during hormone therapy for hypothyroidism

•  Excessive TSH-suppressive therapy

Predominantly, in the first trimester of pregnancy, subclinical hyperthyroidism can be developed in women. However, it's not related to adverse pregnancy outcomes and typically doesn't need treatment. 

Read also What is Hyperthyroidism or Overactive Thyroid

Symptoms

Individuals who have subclinical hyperthyroidism have no symptoms of hyperthyroidism, if, present, they are nonspecific and mild, and may include:

• Tremors generally in fingers and hands
• Nervousness, feeling irritable, or anxiety
• Heart palpitation or rapid heartbeat
• Weight loss
• Intolerance to heat or sweating
• Difficulty in concentration

Diagnosis

If your healthcare providers expect that you have subclinical hyperthyroidism, they will assess TSH levels. If TSH came back to low levels, they will evaluate your T3 and T4 levels to see if they are within the normal ranges.

A blood sample will be required from your arm to perform the tests.

Typically, in adults, the normal reference range for TSH is defined as 0.4 to 4.0 mlU/L (milli international units per liter). However, it's really important to refer to the reference ranges given to you on the laboratory reports. 

Read also What is Hypothyroidism or Underactive Thyroid

Types of hyperthyroidism

Generally, subclinical hypothyroidism is classified into two categories:

Grade 1

People in this category have very low TSH levels but they will be in a detectable amount. It fells under the range between 0.1 and 0.4 mlU/L.

Grade 2

People in this category have TSH values in an undetectable amount which is less than 0.1 mlU/L.

Effects on the body if left untreated

What happens if subclinical hyperthyroidism is left untreated?

You will experience many negative effects in the body, if you left subclinical hyperthyroidism untreated, such as

1. Elevated risks of hyperthyroidism 

People who have undetectable TSH values are at an increased risk of developing hyperthyroidism.

2. Negative cardiovascular effects

People who left subclinical hyperthyroidism untreated can develop:

• Reduced tolerance to exercise
• Elevated heart rate
• Atrial fibrillation 
• Arrhythmias

3. Decreased bone density

In postmenopausal women, untreated subclinical hyperthyroidism may lead to a drop off in bone density.

4. Dementia 

Some research showed untreated subclinical hyperthyroidism can elevate your risk of developing dementia.

Read also What is Thyroid Storm Causes, Treatment, Symptoms

Treatment

How and when it should be treated?

The review of scientific prose found that low TSH values instinctively returned to normal in 50% of the population with subclinical hyperthyroidism.

If anyone has subclinical hyperthyroidism and requires treatment, it will be dependent on:

• The cause
• How severe it is
• The presence of any related complications

1. Treatment based on the causes

Your healthcare provider will evaluate what may be causing your subclinical hyperthyroidism. Deciding the cause can help determine the suitable treatment. 

Treating the external causes of Subclinical Hyperthyroidism

If the cause of subclinical hyperthyroidism is hormonal therapy or TSH-suppressive therapy, your healthcare provider may alter the dosage of these drugs where proper.

Treating internal causes of subclinical hyperthyroidism

Subclinical hyperthyroidism due to thyroiditis normally resolves spontaneously without any further treatment required. If your thyroiditis gets serious, healthcare providers may suggest anti-inflammatory drugs. These could consist of corticosteroids or nonsteroidal anti-inflammatory drugs (NSAIDs).

Medical treatment is needed if you have subclinical hyperthyroidism due to Grave's disease. Your healthcare provider will probably prescribe anti-thyroid medication or radioactive iodine therapy, such as methimazole. This therapy can also be used for the treatment of subclinical hyperthyroidism due to thyroid adenoma or multinodular goiter.

2. Treatment with the presence of complications

If you are experiencing, bone-related or cardiovascular symptoms because of subclinical hyperthyroidism, your healthcare provider may prescribe you bisphosphonates and beta-blockers.

3. Treatment of subclinical hyperthyroidism based on severity

If you have low TSH values but a detectable amount in blood reports and you do not have any complication, your healthcare provider may not suggest you take immediate treatment. Instead, he may decide to reset your TSH levels every few months until they back to normal or he is satisfied that your condition is stable. 

If your TSH values drop into Grade l or Grade ll treatment may be needed and you will be in the risk groups include

• Cardiovascular disease
• Above 65 years of age
• Symptoms suggestive of hyperthyroidism
• Osteoporosis

Your healthcare provider will decide your treatment on the basis of what type of condition is causing your subclinical hyperthyroidism. 

Things you can do at home

If you have subclinical hyperthyroidism probably you lose some weight. It happens because people who have hyperthyroidism (overactive thyroid) have raised BMR (basal metabolic rate). To maintain weight, the calorie requirement will be raised. 

Some research suggested that the negative effects on bone density can be reduced by making sure that you get a sufficient daily dosage of calcium. 

Conclusion

Subclinical hyperthyroidism occurs when you have normal  T3 and T4 levels but low of TSH. Your healthcare provider can use a series of blood tests to come to a diagnosis if you are experiencing subclinical hyperthyroidism symptoms. 

As this condition may be caused by a variety of different situations, your outlook should be excellent.