Lecture 1 Hormones

8/4/2019 Lecture 1 Hormones

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Hormones

PROF. DR. V P SONI

School of Biosciences and BioengineeringIIT BOMBAY


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What are Hormones?

A hormone is a chemical substancethat is secreted into the internal

body fluids by one cell or a group ofcells and has a physiological controleffect on other cells of the body.


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Classification

LOCAL or TROPIC

These hormones havea specific local effects.

Acetylcholinesecreted at the nerveendings

Secretinby theduodenal wall whichincreases waterysecretions of the

pancreas

GENERAL

Secreted by specificendocrine glands

Transported to all partsof the body and causedifferent reactions onall cells or specific cells(target tissue)

GrowthHormonebyanterior pituitary

stimulate all cells Reninsecreted by

kidneys in responseto hypotension affectblood vessels


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Chemical Composition

Three basic types

Steroid Hormones

Most of them derived from cholesterol

Cortisol, Aldosterone, Testosterone, Progesterone,Estrogen.

Derivatives of amino acid Tyrosine Thyroxin, Triidothyronine, Epinephrine, Norepinephrine.

Proteins or Peptides Hormones from anterior pituitary gland, Anti diuretic

hormone, Oxytocin, Insulin, Glucagon, Parathormoneetc.


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Endocrine System

Most of the general hormones are secreted by

the endocrine glands

Endocrine glandsDuct less glands

Functions:

Metabolism and tissue maturation Ion regulation

Water balance

Immune system regulation

Heart rate and blood pressure regulation

Control of blood glucose and other nutrients

Control of reproductive functions

Uterine contractions and milk release


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Endocrine Glands


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Hypothalamus and Pituitary gland


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Hypothalamus and Pituitary gland

The hypothalamus secretes tropic hormones exclusivelyinto the blood vessels within the hypothalamus. Thentravel to anterior pituitary by hypothalamic-hypophysialportal vessels. These tropic hormones are going toaffect the anterior pituitary by their releasing or inhibitingeffects.

Meanwhile, the hypothalamus also produces hormoneswhich are transmitted by nerve signals that terminate in

posterior pituitary gland and cause secretion ofhormones within the posterior pituitary (Oxytocin,Vasopressin or anti-diuretic hormone)


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Hormones secreted by Hypothalamus

affecting anterior pituitary

1. TRH-- Thyrotropin Releasing Hormone

This hormone will affect the anterior pituitary which will then affectthyroid gland activity

2. PIH-- Prolactin Release-Inhibiting HormoneProbably there is also present Prolactin Releasing Hormone;These twohormones will affect the secretion of prolactin from the anterior pituitary

3. CRH-- Corticotropin Releasing HormoneThis hormone affects ACTH release from the anterior pituitary

4. GnRH-- Gonadotropin Releasing HormoneThis hormone will affect the anterior pituitary & cause secretion ofgonadotropic hormnes (Lutieinizing hormone, Follicle stimulatinghormone)

5. GHRH-- Growth Hormone Releasing Hormone6. SS or GHIHSomatostatin or Growth Hormone Inhibiting Hormone

These two hormones affect secretion of growth hormone by the anteriorpituitary


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Pituitary Hormones

Anterior Pituitary

Growth Hormone (GH) Growth of almost all cells and tissues of body

Adrenocorticotropin (ACTH)

Stimulates adrenal cortex to secrete adrenocortical hormones

Thyroid Stimulating Hormone (TSH) Stimulates thyroid gland to secrete thyroxin & triiodothyronine

Follicle Stimulating Hormone (FSH)

Growth of follicles in ovaries/ promotes formation of sperms in

testes Leutenizing Hormone (LH)

Promotes secretion of sex hormones and ovulation

Prolactin

Breast development/ secretion of milk


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Posterior Pituitary

Anti Diuretic Hormone or Vasopressin (ADH)

Causes kidneys to retain water

Deficiency causes Diabetes insipidus

Vasoconstriction to blood pressure

Oxytocin

Uterine contraction during birth process

Milk let-down When baby suckles the nippleand areola of the breast of mother sensory

impluse are transmitted to hypothalamus anddue to reflex action oxytocin and prolactin arereleased ; Oxytocin causes contraction ofmyoepithelial cells of mammary glands alveoliexpressing milk into the ducts


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Thyroid Hormones

Thyroxine (T4) & Tri-ido-thyronine (T3)

Iodine is required to form thyroxin; quantity required is 50 mg iodidespre year or 1mg/wk. Common table salt is iodized with 1 part sodiumiodide per 100,000 parts of sodium chloride.

Functions of thyroid hormone and its effect due to changes in amount

of secretionIncrease in thyroid hormone level called Hyperthyroidism and

decreased levels called hypothyroidism

Increase in transcription of large number of genes

Increase rate metabolism by increasing mitochondria number &

size

Thyroid GlandThyroid stimulating hormone

(TSH) controls thyroid secretion bynegative feedback mechanism


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Thyroid Hormones

Promote growth & development of brain during fetal life & fewyears of postnatal life

Promotes growth in growing children

Increase carbohydrate metabolism Increase fat metabolism, fat stores depleted

Decreases quantity of cholesterol, phospholipids & triglyceridesin plasma

Vitamin need increases due to increased metabolism

Body weight decreased and appetite increased

Vasodilatation, increasing blood flow in body tissues especiallymore in skin to eliminate heat, increase cardiac output and heart

rate, increase strength of heart, slight increase in blood volume. Increased rate and depth of respiration Increased appetite & secretion of digestive juices and motility of

gastrointestinal tract

Increase cerebration so hyperthyroid person has extremenervousness, anxiety complex, extreme worry


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Thyroid Hormones

Slight increase in thyroid hormone makes muscle react with vigor

but excessive quantities cause muscle weakening and less quantitycause muscle to be sluggish & relax

Hyperthyroid person has fine muscle tremors

Hyperthyroid person feel constant tiredness & difficulty in sleeping;in contrast hypothyroid person has extreme somnolence.

In men lack of thyroid hormone cause loss of libido and on otherhand excess amount cause impotence

In women lack of thyroid hormone cause menorrhagia &polymenorrhagia (excessive & frequent menstrual bleeding),decreased libido and excess amount cause oligomenorrhea &occasionally amenorrhea

In hypothyroidism gland increase in size condition called Goiter

Calcitonin

Promotes deposition of Calcium in bones and thereby decreaseCalcium concentration in ECF


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Regulation of Thyroid Hormones (Negative

feedback mechanism)

Hypothalamus

Anterior pituitary gland

Thyroid Gland

T3, T4

TRH

TSH

+ve

+ve

-ve

-ve

Iodide+ve

Somatostatin

-ve


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Parathyroid Hormone

Parathyroid Gland

ParathormoneControls calcium concentration in ECF1. Absorption of Ca through gut

2. Tubular resorption of Ca by kidneys

3. Release of calcium from bones


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Parathyroid & Calcitonin Hormones

(Regulation of Calcium)


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Islets of Langerhans in the Pancreas

Insulin

Secreted by cells of islets ofLangerhans

Promotes glucose entry intomost cells of the body.

Deficiency causes Diabetes

mellitus

Glucagon Secreted by cells Increases the release and synthesis of glucose from the liverinto circulating body fluids


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Adrenal Gland

Adrenal Cortex

Cortisol

Multiple metabolic functions(fats, protein and carbohydrates)

Aldosterone Reduces Sodium excretion by

kidneys

Increases Potassium excretion

Adrenal Medullae Epinephrine/ Nor epinephrine

Constriction of blood vesselsand increase in arterial

pressure


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Hormones of Reproductive System

Testes

Testosterone Stimulate growth of male sex organs

Promotes development of secondary sexualcharacteristics

Ovaries

Estrogen Stimulate development of female sex

organs and secondary sexualcharacteristics

Development of breasts mammaryglands plus deposition of fat around it

Progesterone

Preparation of uterus for pregnancy

Promotes development of secretary

apparatus i.e. lobule alveolar systemof the breast


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THANK YOU

Lecture 1 Hormones

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