Mechanism of Action of Peptide and Steroid Hormones

What are Peptide Hormones?

Peptide hormones are polymers comprising small chains of amino acids. Endocrine glands in the human body produce various peptide hormones like insulin, glucagon, somatostatin, ghrelin, oxytocin, etc. that are circulated in the bloodstream. These hormones bind to the tissues in the target organs. For instance, the LH hormone produced by the anterior pituitary gland targets the Leydig cells of ovaries in a pregnant woman. Similarly, corticotrophins release the cortisol or stress hormone which has adverse effects on testosterone in males.

Mechanism of Action of Peptides

Peptide hormones are known for their second messenger function within the target organs. Second messengers are the small molecules or ions that help to carry signals from the cell surface receptors to the effector proteins. After the release of peptide hormones in the bloodstream, the course of action begins in the plasma membrane of the cells. This starts the procedure of intracellular signalling pathways that are extremely sensitive to external stimuli. The pathway forms a bridge between the cell surface and the nucleus. They are capable of modifying gene expressions. Peptides regulate physiological processes like metabolism, stress, reproduction, and growth.

Peptide Hormones in Humans

Human bodies have traces of more than 60 peptides. Let us discuss the functionality of a few:

Corticotropin or ACTH is responsible for the increased production of cortisol or stress hormones. It is secreted from the anterior pituitary gland as a side-effect of biological stress.

Ghrelin or ‘hunger hormone’ promotes the desire to eat more. It is produced in the enteroendocrine cells of the pancreas. It also stimulates the production of stomach acids.

Insulin or the main anabolic hormone inside the body acts as a guiding factor in the regulation of blood sugar levels. They help in the absorption of glucose into the liver or muscles and convert them into either proteins or fats. Insulin is released from the beta cells of pancreas islets.

Follicle-stimulating Hormone (FSH) is produced in the gonad cells of the anterior pituitary gland. It matures the reproductive system.

What are Steroid Hormones?

Steroid hormones are synthesised within the adrenal glands or gonads in the human body. They are responsible for maintaining the fundamental physiological processes of metabolism, pH balance, immunity protection, and normalising inflammation. Some steroid hormones examples in humans are androgen, oestrogen, and progesterone secreted from both male and female gonads. Although our body produces this class of hormones sufficiently, they still find uses in the therapeutic field. Incorporating these steroids in health supplements is considered to be illegal and the athletes who abuse these external steroids for performance enhancement are found to be guilty.

Mechanism of Action of Steroid Hormones

Good quality cholesterol or HDL (high-density lipoprotein) intake through a balanced diet should be optimum for the efficient functioning of the adrenal glands and gonads. The mechanism of action of peptide and steroid hormones proves to be contrasting. These lipids easily get absorbed in the cells by fat solubility where they interact with steroid hormone receptors. The resultant steroid hormones are released in blood before being attached to particular carrier proteins. Sex hormones are produced by this process.

 Steroid hormone examples in males include testosterone, androstenedione, estradiol, and estrone. While in the female body we find traces of progesterone, estradiol, and estrone sulphate. They are secreted in different stages of the monthly cycle namely follicular, luteal, and postmenopause phases.

Glucocorticoid Hormones: Overview

Glucocorticoid hormones, popularly marketed as glucocorticoids (GCs), are external steroid hormones that are used to cure autoimmune diseases, cancer, and intracellular chronic inflammation. This family of hormones is indispensable for carbohydrate metabolism in the human body by initiating the process of gluconeogenesis.

 The three primary components of glucocorticoid hormones are: 

• N terminal transactivation domain of the oestrogen receptors in both males and females (NRs)
• DNA binding domain (DBD)
• Ligand binding domain (LBD)

GCs bind to the receptors for transcription. The cellular genomes of glucocorticoids are bound to their cognate receptors (GRs). They prove to be efficient against an overactive immune system. Typical dosage ranges between 8-9 milligrams a day for adults. Health benefits are noticed after several weeks of usage. Some examples of glucocorticoid hormones are betamethasone, hydrocortisone, prednisolone, and dexamethasone.

The prescribed dosage of synthetic glucocorticoid hormones takes care of the immune system by suppressing chronic inflammation. Owing to the distinct orientation of sexual hormones in males and females GCs tend to act differently against autoimmune diseases (AD). Arthritis, type 1 diabetes, atrophic gastritis are some of the ADs that can be treated with GCs. Due to its proven health benefits, scientists have termed GC as a life-saving hormone.

The relation between sex hormones and glucocorticoid hormones is debatable as both the families of hormones exert influence over the immunity system. 

Conclusion

By polarity, peptides experience trouble when they try to penetrate the cell membrane. On the other hand, it is a cakewalk for the steroid hormones as they are fat-soluble. Owing to failure, peptide hormones tend to attach themselves with receptors fixed outside the cell membrane. Though the mechanism of action of peptide and steroid hormones are dissimilar, both of them are signalling modules that facilitate the physiological processes and regulate the behaviour of various organs. Also, their origin and mode of transport are the same. Glucocorticoids help us to combat numerous health problems. They are renowned for their immunosuppressant effects.