European Journal of Biomedical and Pharmaceutical Sciences

BIOCHEMICAL ASPECTS AND INTERPRETATION OF THYROID STIMULATING HORMONE IN THYROID DYSFUNCTIONS

Dr. R. Dhananjayan*

ABSTRACT

The thyroid gland is responsible for the formation and secretion of thyroid hormones as well as iodine homeostasis
within human body. It is responsible for adjusting metabolic rate of the body. The thyroid produces approximately
90% inactive thyroid hormone or thyroxine (T4) and 10% active thyroid hormone or triiodothyronine (T3).
Thyroid Stimulating Hormone (TSH) is a hormone released by pituitary gland which triggers thyroid to produce
and release its own hormones T4 and T3. It aids in identifying subjects who suffer from thyroid malfunction.
Thyrotropin Releasing Hormone (TRH) is secreted from the hypothalamus and reaches the anterior pituitary via
the hypophyseal portal circulation. Activation of receptors stimulates the release of TSH which activates its own
receptors on the follicular cells of the thyroid gland. TSH is the primary biomarker for the diagnosis of thyroid
dysfunction and for guiding treatment of thyroid diseases. This paper focuses on the functions, diagnostic
importance, diurnal and circannual variations in TSH levels.

Keywords: TSH, T3, T4, TRH, Thyroid Dysfunction, Thyroid Function Tests.