World Thyroid Day 2022: Know How Thyroid-Stimulating Hormone Or TSH Affects Hypothyroidism

Thyroid-stimulating hormone (TSH) is a pituitary hormone that stimulates the thyroid gland to produce thyroxine. When thyroid levels in our body are low, the pituitary gland makes more TSH.

Hypothyroidism is thyroid hormone deficiency, a condition in which your thyroid gland does not produce enough of certain crucial hormones. It is diagnosed by clinical features such as a typical facial appearance, hoarse slow speech, dry skin, and low levels of thyroid hormones.

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By Dr Rajesh Bendre

Hypothyroidism is thyroid hormone deficiency, a condition in which your thyroid gland does not produce enough of certain crucial hormones. It is diagnosed by clinical features such as a typical facial appearance, hoarse slow speech, dry skin, and low levels of thyroid hormones. Management for this condition includes the administration of thyroxine. High TSH levels can mean your thyroid gland is not making enough thyroid hormones, a condition called Hypothyroidism. Conversely, low TSH levels can mean your thyroid is making too much of the hormones; this state is called hyperthyroidism. Therefore, an imbalance in TSH level can lead to different thyroid disorders.

Thyroid-stimulating hormone (TSH) is a pituitary hormone that stimulates the thyroid gland to produce thyroxine. When thyroid levels in our body are low, the pituitary gland makes more TSH. Conversely, when thyroid levels in our body are high, the pituitary gland makes less TSH.

As thyroxine is an essential hormone for regulating heart rate, digestion, physical growth and brain development and functioning, an insufficient supply to cells can disrupt cellular metabolism throughout the body, leading to organ and tissue damage and resulting in life-threatening complications. Henceforth, hyperthyroidism can lead to other comorbid conditions.

The symptoms of hypothyroidism are generally nonspecific, with considerable overlap with other conditions and with the consequences for the health of advancing age. Therefore, these symptoms do not help identify Hypothyroidism, and a thyroid function test is required for a firm clinical diagnosis. Unfortunately, a lack of knowledge and awareness of Hypothyroidism and a common tendency in people to attribute the symptoms of Hypothyroidism to other causes has led to a late diagnosis of Hypothyroidism.

In approximately 95% of cases, Hypothyroidism is a problem in the thyroid gland and is called primary hypothyroidism. In some cases, hypothyroidism results from the decrease in thyroid-stimulating hormone (TSH) production by the pituitary gland, called secondary hypothyroidism.

High TSH increases the risk for poor hospital outcomes. Therefore, it is essential to maintain optimal thyroid hormone replacement in patients with hypothyroidism to avoid severe consequences.

Hypothyroidism was not diagnosed until symptoms had been present for a long time in the past. However, simple blood tests can now detect hypothyroidism at an early stage. A person may be tested for hypothyroidism if there are signs and symptoms, such as those discussed above, or a screening test.

Blood Test

Blood tests can confirm the diagnosis and pinpoint the underlying cause of the thyroid hormone deficiency. The most common blood test for hypothyroidism is thyroid-stimulating hormone (TSH). Sample should be given preferably in the morning with fasting (8-10hrs) condition. TSH is the most sensitive test because it can elevate even with a slight decrease in thyroid function. Existing TSH testing platforms are well standardised and are very sensitive (Ultra-sensitive) assays using chemiluminescence as the testing principle. 

High TSH levels (above 10mIU/ml) are often suggestive of hypothyroidism, Conversely, Low TSH levels (below 0.1 mIU/ml) are often indicative of hyperthyroidism. However, TSH also shows considerable physiological (Biological) variation, which can cause difficulty in interpretation in some cases. Hence, TSH test is often clubbed with Free T4 (FT4) assay for better correlation and interpretation.

 The author is Chief Pathologist, Neuberg Diagnostics, Chembur, Mumbai