Classification of hormones - class-XII

• Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood(ductless) rather than through a duct.
•  The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands. Hence, Ductless gland is a feature of endocrine glands.

Hormones can be classified based on their chemical nature like amino acid derivative hormones, peptide hormones, iodothyronines and steroid hormones. Hormones like epinephrine, norepinephrine, thyroxine are derived from amino acids. Epinephrine and norepinephrine are released by renal medulla. These are derived from single amino acid tyrosine. Thyroxine is released by thyroid gland. It is also derived from tyrosine amino acid by the addition of iodine.

The secretion of gonadotropin s (LH & FSH) increase gradually during the follicular phase and stimulates follicular development as well as secretion of oestrogens and progesterone. 

When the blood pressure is increased it results in excess of blood flow to the Heart. When the blood flow to the heart is increased it leads to the stretching of the atrial wall and the release of ANF (Atrial natriuretic polypeptide) from the atrial walls. The ANF is a polypeptide hormone which causes the vasodilation (dilation of blood vessels) and thereby decrease the blood pressure. Hence ANF is a peptide hormone which is secreted by the atrial wall of the heart when blood pressure is increased and causes dilation of the blood vessels which results in the decrease of the blood pressure.

Antidiuretic hormone (ADH), also known as vasopressin, is primarily responsible for increasing water reabsorption in the distal convoluted tubules and collecting ducts of the kidney. This action helps the body retain water and concentrate urine.

Hormones are chemical messengers secreted by endocrine glands into the bloodstream or equivalent circulatory channels. This internal transport system distributes them to target organs and tissues throughout the body.

Steroid hormones are lipid soluble and pass easily through the cell membrane to bind to intracellular receptors. This hormone receptor complex then enters the nucleus and directly stimulates mRNA transcription.

Peptide hormones are the one which have single or multiple long amino acid chain/s. Insulin is a peptide hormone with two amino acid chains, one with 21 and other with 30 amino acids. This makes option B correct. 

Hormones are certain essential substances in our bodies that are released by our body's endocrine system.  They are chemical messengers in our bodies that transmit messages for the action of various glands in our bodies and their secretions. 

The chief function of STH (GH) is to promote synthesis and secretion of small protein hormone called insulin like growth factors (IGFs).

The chromatin cells of adrenal medulla synthesize two hormones adrenaline or epinephrine (80%) and noradrenaline or norepinephrine (20%).

Hormones are also grouped into three general structures as follows:

1. Steroid hormones are fat-soluble molecules made from cholesterol. Among these are the three major sex hormones groups: estrogens, androgens and progesterones. Males and females make all three, just in different amounts. Steroids pass into a cell's nucleus, bind to specific receptors and genes and trigger the cell to make proteins.
2. Amino acid derivatives, such as epinephrine, are water-soluble molecules derived from amino acids (the building blocks of protein). These hormones are stored in endocrine cells until needed. They act by binding to protein receptors on the outside surface of the cell. The binding alerts a second messenger molecule inside the cell that activates enzymes and other cellular proteins or influences gene expression.
3. Insulin, growth hormone, prolactin and other water-soluble polypeptide hormones consist of long chains of amino acids, from several to 200 amino acids long. They are stored in endocrine cells until needed to regulate such processes as metabolism, lactation, growth and reproduction.

In the signaling pathway involving calcium, cAMP, DAG, and IP3 are common second messengers. Phospholipase C is an enzyme that generates DAG and IP3, not a second messenger itself.

Steroid hormones are derived from cholesterol and are lipid-soluble molecules. Examples of steroid hormones include the sex hormones (androgens, oestrogens, and progesterone). Oestrogens helps in development and maintenance of an individual's feminine characteristics. Whereas, insulin, glucagon, and thyroxin are the protein hormone 

The supraoptic nuclei of the hypothalamus primarily synthesize ADH (vasopressin), while the paraventricular nuclei primarily synthesize oxytocin. Both are transported to and released by the posterior pituitary.

Steroid hormones are derived from cholesterol and are hydrophobic (lipid-soluble). This property allows them to diffuse directly through the lipid bilayer of the plasma membrane.

Hormones produce their effects on target tissues by binding to specific proteins called hormone receptors located in the target tissue only. Hormone receptors present on the cell membrane of the target cells are called membrane-bound receptors and the receptors present inside the target cell are called intracellular receptors, mostly nuclear receptors (present in the nucleus. 

Angiotensin II - is a vasoconstrictor which causes an increase in BP (means a decrease in blood volume),  increase Na+ reabsorption, does not alter GFR, Angiotensin II can stimulate aldosterone secretion. 

Glucocorticoids stimulate, gluconeogenesis, lipolysis, and proteolysis; and inhibit cellular uptake and utilization of amino acids. Cortisol is involved in maintaining the cardiovascular system as well as the kidney functions. Glucocorticoids, particularly cortisol, produces anti-inflammatory reactions and suppress the immune response. Cortisol stimulates the RBC production.

So, the correct answer is ' Option A '

Hypothyroidism is a disorder caused due to deficiency of thyroid hormone. It may lead to cretinism, myxoedema, simple goitre, Hashimoto's disease. Exopthalamic goitre is thyroid enlargement in which thyroid secretes excessive amount of thyroid hormone. It is caused due to hypersecretion of thyroid hormone.

The oxytocin  is a G protein coupled receptor which requires Mg2+ and cholesterol. It belongs to the rhodopsin-type group of G protein coupled  receptors. The peripheral actions of oxytocin mainly reflect secretion from the pituitary gland. Chemical nature of oxytocin is proteinaceous . So the correct answer is 'Oxytocin' 

Polypeptide hormones are hormones made up of amino acids that are secreted by the endocrine system and distributed to end organs through the circulating blood. Endocrine organs that secrete peptide hormones include the hypothalamus, pituitary gland, thyroid gland, adrenals, ovaries, endocrine pancreas, and adipose tissues.

(i) Peptides: These hormones are further of two types: Short peptide and long peptide.