Test: Human Endocrine System - NEET

Thyroxine and Triiodothyronine are iodinated form of an amino acid called tyrosine

Glucagon increases blood sugar level. It is secreted by α-cells of islets of Langerhans of pancreas (heterocrine gland).

Thyroid gland stores its hormones in the colloid. Colloid is a homogenous material present in the thyroid follicles of thyroid gland.

Prolactin

Explanation: Prolactin is a hormone produced by the pituitary gland that stimulates the mammary glands in the breasts to produce milk. It is responsible for the growth and development of mammary glands during pregnancy and the secretion of milk after childbirth. Oxytocin, on the other hand, is responsible for the release of milk from the mammary glands during breastfeeding (milk let-down reflex).

Thyroid hormones, thyroxine and tri-iodothyronine regulate the basal metabolism of our body.

Gonadotropic hormones (LH and FSH), secreted by anterior lobe of pituitary regulate growth and activity of gonads.

Luteinising hormone (LH) secreted by the anterior lobe of pituitary gland stimulates corpus luteum of the ovary to secrete progesterone.

Oxytocin, secreted by the posterior pituitary gland causes contraction of smooth muscles of the uterus during child birth.

Secretin hormone is secreted by the Brunner's glands present in the wall of the duodenum.

• Regulates the development, maturation and functions of epididymis, vas deferens, seminal vesicle, prostate gland, urethra, etc.


• Stimulates muscular growth of facial and axillary hair, aggressiveness, low pitch of voice, etc.


• Stimulates spermatogenesis.


• Acts on CNS and sexual behavior (libido).


• Produces anabolic (synthetic) effect on protein and carbohydrate metabolism.


• The Leydig's cells/interstitial cells (present in intertubular space) secrete this hormone under the influence of LH.

Based on the given functions, the hormone being referred to is Androgen.

Androgen is a group of hormones that play a crucial role in the development and maintenance of male characteristics and reproductive function.

Some examples of androgens include testosterone and dihydrotestosterone (DHT). Testosterone is primarily produced in the testes, while DHT is synthesized from testosterone in various tissues.

Androgens are responsible for the development of secondary sexual characteristics in males, such as facial and body hair growth, deepening of the voice, and increased muscle mass.

They also play a vital role in spermatogenesis, the production of sperm cells, and are involved in regulating sexual behavior and libido.

Additionally, androgens have an anabolic effect, promoting protein synthesis and carbohydrate metabolism.

The Leydig's cells, located in the intertubular space of the testes, secrete androgens under the influence of luteinizing hormone (LH) from the pituitary gland.

Therefore, based on the given statements, the hormone referred to is Androgen.

Middle lobe of pituitary secretes MSH (melanocyte stimulating hormone) that controls the synthesis of melanin granules in the chromatophores.

Adrenaline prepares the body for emergency reactions like fight and flight. Therefore, it directly affects the SA node to increase the rate of heart beat.

Sertoli cells are regulated by FSH secreted by the anterior pituitary.

Adrenaline (Epinephrine) hormone is secreted by adrenal medulla under the conditions of emergency. Therefore, it is also known as emergency hormone. During emergency, it is released and causes dilation of blood vessels, so that the blood flow is increased. It also increases heart beat so that more oxygen is consumed and it also increases blood glucose level.

Parathyroid glands located behind the thyroid gland, produce a hormone called parathormone. This hormone maintains calcium and phosphorus balance in the body. Thus, if a person is having problem with calcium and phosphorus metabolism in the body, this means, his parathyroid gland is not functioning properly.

Parathormone secreted by parathyroid gland regulates the level of calcium in the blood. It stimulates the release of calcium from the bones into the blood, increases calcium absorption from the intestine into the blood and it also increases calcium reabsorption from the nephrons into the blood. Therefore, its deficiency leads to low blood calcium level.

Vasopressin (antidiuretic hormone, ADH) released from posterior pituitary increases reabsorption of water from distal and collecting tubules of the kidney, thus, helping in producing concentrated urine. If there is hyposecretion of vasopressin, then water will not be reabsorbed from the tubules and the urine thus produced will be dilute. This disorder is called diabetes insipidus which is characterised by producing dilute urine several times a day.

The neurosecretory cells of the hypothalamus secrete releasing factors (neurohormones) that regulate the secretion of hormones from the anterior pituitary.

Insulin, glucagon and somatostatin, are secreted by islets of Langerhans of pancreas, Somatostatin suppresses the release of other hormones from pancreas.

In diabetes mellitus, a patient is unable to produce or utilise insulin hormone. This hormone helps in maintaining the level of glucose in the blood by converting extra glucose into glycogen. Thus, in diabetes mellitus, the body of the patient becomes incapable to store glucose in the form of glycogen. Therefore, he starts excreting glucose in the urine. If a patient kept on a carbohydrate-free diet is excreting glucose in the urine, then this means, high level of glucose in the blood not only depends on dietary carbohydrates but also on glycogenolysis (breakdown of glycogen into glucose in the liver) and gluconeogenesis(breakdown of fats into glucose in adipose tissues).

Adrenocorticotropic hormone is secreted by anterior pituitary. This hormone stimulates adrenal cortex to secrete its hormones.

Islets of Langerhans are found in pancreas. It consists of four types of cells - alpha cells that secrete glucagon, β-cells that secrete insulin, delta cells that secrete somatostatin and F cells that secrete pancreatic polypeptide.

Ovulation in females is under the control of luteinsing hormone (LH). Secreted by the anterior pituitary gland. It also stimulates development of corpus luteum.

Pineal body is a very small, reddish-grey, vascular, conical, solid body located in the brain. It secretes a hormone named melatonin. Melatonin makes the skin colour lighter in certain animals and also regulates the functioning of gonads, thus, controls sexual behaviour and regulates the period of puberty.

Goitre is caused due to the deficiency of iodine in the diet. Iodine is needed for the synthesis of thyroxine secreted by thyroid gland. The production of this hormone decreases with poor iodine diet. This causes enlargement of thyroid gland which is called goitre.

Insulin hormone produced by beta cells of pancreas, is central to regulating carbohydrate metabolism in the body. It causes cells in the skeletal muscles, and fat tissue to absorb glucose from the blood.

Thymus gland is a prominent gland at birth but gradually atrophies in the adult. It is a soft, pinkish, bilobed mass of lymphoid tissue. It secretes a hormone thymosin which is involved in producing immunity.

Calcitonin is a hormone secreted by the thyroid gland. It lowers the calcium level in the blood by suppressing the release of calcium ions from the bones.

Adrenal gland is called the emergency gland of the body. Adrenaline is secreted by adrenal medulla on stimulation by sympathetic nervous system for meeting an emergency of stress condition, like injury, pain fear, Accident, grief, fall in blood pressure etc. Hence adrenal gland is called emergency hormone.

Thyroid stimulating hormone (TSH) is produced by the anterior lobe of the pituitary and it stimulates production and secretion of thyroid hormones.

Calcium plays an important role in blood clotting. Parathormone, a hormone released by parathyroid glands, increases calcium level in the blood. Therefore, deficiency of this hormone will decrease Ca²⁺ level in blood, thus leading to delay in blood clotting and increase in bleeding time.

Estrogen, secreted by ovaries in females, stimulates the development of secondary sexual characters during puberty and maintains them through the reproductive years of adult life in females Testosterone is produced by testes in males, it stimulates the development of male secondary sexual characters like beard, moustache, etc.

Somatostatin is an inhibitory hormone which is secreted by hypothalamus in the brain and pancreas. Somatostatin from hypothalamus inhibits the secretion of growth hormone from the anterior lobe of pituitary. Somatostatin from pancreas inhibits the release of other hormones from pancreas like insulin and glucagon.

Growth hormone secreted by the anterior pituitary has a widespread effect in the body it stimulates growth of various body cells, promotes protein anabolism, absorption of calcium from bowel and conversion of glycogen to glucose.

Feedback control is a mechanism by which secretion of hormones is under the control of factors or other hormones. When the level of epinephrine decreases in the blood, it stimulates the hypothalamus to secrete more CRH which results in increased production of ACTH from anterior lobe of pituitary which in turn stimulates the increased production of epinephrine from adrenal medulla.

Aldosterone (secreted by adrenal medulla) acts mainly on the renal tubules and stimulates the reabsorption of Na⁺ and water and excretion of K⁺ and phosphate ions.

When secretion of hormones is under the control of factors or other hormones, it is called the feedback control. If the level of progesterone and estrogen is low in the blood, it stimulates the hypothalamus to secrete more FSH-RH which results in increased production of FSH from anterior pituitary which in turn stimulates the increased secretion of estrogen and progesterone from ovary.

Hormones of testes and gonads are steroid in nature. They are derived from cholesterol.

Growth hormone(GH) secreted by anterior pituitary promotes cell division, protein synthesis and bone growth.