What is the Difference Between TRH and TSH

The key difference between TRH and TSH is that TRH is a hormone that stimulates thyrotropin cells in the anterior pituitary to release thyroid-stimulating hormone and prolactin, while TSH is a hormone that stimulates the thyroid gland to produce and release thyroid hormones called T4 and T3.

TRH and TSH are two hormones associated functionally. This is because TRH is the hormone that triggers the release of TSH from the pituitary. Normally, the hypothalamus releases a thyroid-releasing hormone called TRH, which in turn stimulates the pituitary gland to produce and release thyroid-stimulating hormone (TSH). Later, TSH triggers the thyroid to produce thyroid hormones such as T3 and T4.

CONTENTS

1. Overview and Key Difference
2. What is TRH 
3. What is TSH
4. Similarities – TRH and TSH
5. TRH vs. TSH in Tabular Form
6. FAQ – TRH and TSH
7. Summary – TRH vs. TSH

What is TRH?

TRH is a tripeptide hormone produced by neurons in the hypothalamus. TRH stimulates the release of thyroid-stimulating hormone (TSH) and prolactin from the anterior pituitary. The structure of this hormone was first determined and synthesized in 1969 by Roger Guillemin and Andrew V. Schally.

TRH is clinically used for the treatment of spinocerebellar degeneration and disturbance of consciousness in humans. The pharmaceutical form of this hormone is protirelin. However, people may have side effects when TRH is used in clinical treatments, such as nausea, flushing, urinary urgency, mild rise in blood pressure, shaking, sweating, shivering, and restlessness.

What is TSH?

TSH, or thyroid stimulating hormone, also referred to as thyrotropin, is a hormone that the pituitary gland releases to trigger the thyroid to produce and release its own hormones, such as thyroxine (T4) and triiodothyronine (T3). Adults have a normal TSH range of around 0.27 to 4.2 uIU/mL in the blood. Moreover, healthcare providers test TSH levels using a test called the TSH blood test.

TSH is a glycoprotein that consists of two subunits: alpha and the beta subunit. TSH was first discovered by Bennett M. Allen and Philip E. Smith in 1916. The standardized purification of TSH was done in 1937 by Charles George Lambie and Victor Trikojus at the University of Sydney.

TSH normal values range from 0.5 to 5.0 mIU/L. Clinically, TSH level is very important as low levels of TSH are associated with hyperthyroidism, and high level of TSH is associated with hypothyroidism. Furthermore, a synthetic drug called recombinant human TSH alpha or Thyrogen is used when preparing for RAI ablation or in monitoring the recurrence of thyroid cancer. However, this drug can cause some side effects such as inability to move legs or arms, paralysis of one side of the body, faintness, feeling of warmth, skin rash, hives, welts, itching, or redness, loss of vision, redness of the face, neck, arms and upper chest and tightness of the throat.

What are the Similarities Between TRH and TSH?

• TRH and TSH are two hormones associated functionally.
• TRH is the hormone that triggers the release of TSH from the pituitary.
• Both these hormones are commercially used.
• The synthetic forms of both these hormones have side effects.

What is the Difference Between TRH and TSH?

TRH is a hormone that stimulates thyrotropin cells in the anterior pituitary to release thyroid-stimulating hormones and prolactin, while TSH is a hormone that stimulates the thyroid gland to produce and release thyroid hormones called T4 and T3. Thus, this is the key difference between TRH and TSH. Furthermore, TRH is a tripeptide, while TSH is a glycoprotein that consists of two subunits: alpha and beta subunit.

The infographic below presents the differences between TRH and TSH in tabular form for side-by-side comparison.

FAQ: TRH and TSH

Why is TRH high in hypothyroidism?

In hypothyroidism, the loss of thyroxin feedback inhibition causes overproduction of TRH. Hence, TRH is high in hypothyroidism.

Is thyrotropin the same as TSH?

Thyrotrophin is another name for TSH.

What is the main function of the TSH?

TSH regulates the production of hormones from the thyroid gland.

Summary – TRH vs. TSH

The thyroid hormone (T3 and T4) controls the metabolism of the body, where the body transforms food that people eat for energy.  Thyroid hormone is produced through a feedback loop where the hypothalamus first releases thyroid-releasing hormone (TRH), which, in turn, stimulates the pituitary gland to produce and release thyroid-stimulating hormone (TSH). TSH then induces the thyroid to produce T4 and T3. Therefore, TRH and TSH are two hormones associated functionally. Moreover, TRH is a tripeptide, while TSH is a glycoprotein that consists of two subunits: alpha and beta subunit. So, this summarizes what is the difference between TRH and TSH.

Reference:

1. “Thyrotropin-Releasing Hormone.” An Overview | ScienceDirect.
2. “TSH (Thyroid-Stimulating Hormone) Levels: Symptoms.” Cleveland Clinic.

Image Courtesy:

1. “Thyrotropin-releasing hormone” By Fvasconcellos – Own work (Public Domain) via Commons Wikimedia
2. “Thyroid System” By Mikael Häggström  (Public Domain) via Commons Wikimedia