What is Hormonal Regulation?

The hormones are generated in the body for controlling various biochemical reactions, which are concerned with the maintenance of homeostasis. The hormones regulate the physiological and behavioral processes of the body. The reactions including respiration, metabolism, digestion, reproduction, and movement are found to be regulated by the action of the hormone.

Different Modes of Hormonal Signaling

The effect of the hormones is depended upon the region of discharge and the gland concerned with the release. The hormones are grouped based on these two factors. The discharge mode is found to be different for each hormone. The types of hormone signaling that have been identified include paracrine, endocrine, autocrine, and intracrine.

• The endocrine hormones are found to be discharged on the bloodstream, where the blood carries the hormones to the specific receptor sites found on the cell.
• The paracrine signaling takes place as the cells discharge the signaling factors to adjoin with the receptors identified in the nearby cells. They do not require the bloodstream for aiding in their movement.
• The autocrine hormonal signaling takes place as hormones are discharged from the cells and these hormones connect with the receptors found on the same cell. The biochemical reaction is initiated in the same cell concerning the discharge of the hormone.
• The intracrine signaling takes place as the discharge and binding of the hormone occur intracellularly. Different glands are concerned with the discharge of different hormones in the body. 

Classes of Hormones

They are composed of amino acid chains and are produced through the transcription and translation of a particular gene in the nucleus. The number of amino acids identified in these types of hormones ranges between three to a hundred. The structure of these hormones is altered to an active form through a process called post-translational modification. Most of these hormones are packed in the form of a vesicle and this process takes place in the Golgi apparatus of the cell. These hormones are hydrophilic and cannot pass through the plasma membrane of the cell. Thus, the receptors of these hormones are found in the external membrane of the cell. Some of the hormones are derived from amino acids and are known as amino acid derivates. They are also accumulated in the vesicles and the examples encompass thyroxine and melatonin.

The steroid hormones are hormones derived from lipid precursors. They possess the capacity to move through the lipid bilayer of the plasma membrane and the receptors of these hormones reside in the cytoplasm and nucleus of the cell. Examples of steroid hormones include testosterone, cortisol, and estradiol. The eicosanoid hormones are formed from the lipids occluding the prostaglandins, lipoxins, and arachidonic action. The lipoxygenases and the cyclooxygenases are concerned with the discharge of these types of hormones. They are hydrophobic and fuse with the receptors identified in the membrane of the cell.

Receptors of Hormones

The hormones are classified based on the type of receptors: intracellular receptors and intercellular receptors. The intercellular receptors are positioned on the external surface of the plasma membrane and the intracellular receptors reside on the cytoplasm and or the nucleus of the cell. The cells are found to possess diverse receptors to link to different hormones. The receptors for the peptide hormones are detected in the plasma membrane and the receptors for the steroid hormone are found in the cytosol. The receptor identified in the external layer of the plasma membrane is associated with a G-protein on the internal surface. The binding of the specific peptide hormone will initiate the G protein-coupled receptor to discharge a secondary signaling molecule into the cytoplasm of the cell. This molecule connects with the receptor present in the nucleus and initiates gene expression. The cyclic AMP (adenosine monophosphate) is the most common secondary messenger discharged from the G protein-coupled receptors.

The steroid hormone does not require the presence of a secondary messenger for completing their action. The non-polar nature of steroid hormone allows it to move through the plasma membrane and directly trigger gene expression in the cell.

Regulatory Mechanism

The hormones are discharged to sustain the homeostasis in the body. They are classified according to the mode of regulation. Some of the hormones are positively regulated while the others are negatively regulated. The mechanism of hormone regulation includes the negative feedback and positive feedback processes. The negative feedback takes place as the product of the reaction tends to minimize the stimulus that triggered the formation of the product. The positive feedback mechanism takes place as the product of the mechanism has a promoting effect upon the same reaction. The control of the blood sugar levels in the body is mediated through the negative feedback mechanism, where the hormone insulin is discharged during the excess blood sugar levels and the hormone glucagon is discharged during the insufficient blood sugar.

Context and Applications  

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for

• Bachelors in Biology
• Bachelors in Biochemistry
• Masters in Biochemistry

Related Concepts

Cytokine, Endocrinology, Endocrine disruptor