Steroids Lecture 1-3

What are steroids?

Steroids are natural compounds found in animals and plants that belong to the lipid family.

What do steroids do in the body?

They act as hormones, control metabolism, and help maintain cell structure.

What are the main things we study about steroids?

Their structure, function, chemistry, transport, metabolism, and medical uses.

what are the main things we study about steroids?

their structure, function, chemistry, transport, metabolism, and medical uses.

where do steroids come from?

from triterpenoids — their starting molecule is squalene.

how is squalene formed?

by joining two molecules of farnesyl pyrophosphate together.

what is the basic structure of a steroid?

four fused carbon rings — three six-membered rings and one five-membered ring.

why is this structure important?

it makes steroids strong, stable, and gives them a specific 3d shape.

what are the main functions of steroids in living things?

they regulate hormones, metabolism, inflammation, salt balance, and sexual development.

what are sterols?

steroids with an alcohol group (–oh), such as cholesterol.

what is the function of cholesterol?

it is found in all animal cells, helps form membranes, and is the base for all other steroid hormones.

why can cholesterol be harmful?

too much cholesterol can build up in blood vessels, causing gallstones and atherosclerosis (hardening of arteries).

what are saponins?

plant steroids with sugar chains that act like soaps (surfactants).

are saponins safe?

most are harmless but can break red blood cells if too concentrated.

what are cardioactive glycosides?

plant-based steroids used to treat heart conditions like atrial fibrillation.

how do they help the heart?

they strengthen heart contractions and regulate heartbeat.

what are bile acids?

steroids that help digest fats in the gut and remove cholesterol from the body.

what happens if bile acids don’t work properly?

cholesterol can build up and form gallstones.

what are the two main groups of steroid hormones?

sex hormones and corticosteroids (from the adrenal cortex)

what are female sex hormones called?

oestrogens (like estradiol) and progestogens (like progesterone).

what do female sex hormones do?

they regulate the menstrual cycle, ovulation, and pregnancy.

what are male sex hormones called?

androgens, mainly testosterone.

what do male hormones do?

they control male traits and increase muscle and bone growth.

what are corticosteroids?

hormones made by the adrenal gland that include glucocorticoids and mineralocorticoids.

what is a glucocorticoid?

a hormone like cortisol that controls blood sugar, metabolism, and inflammation.

what is a mineralocorticoid?

a hormone like aldosterone that controls salt and water balance in the body.

are steroids water-soluble?

no, they are mostly nonpolar and dissolve in fats or organic solvents.

how do steroids move through the blood if they’re not water-soluble?

they attach to carrier proteins that transport them.

what are the main steroid transport proteins?

• shbg (sex hormone binding globulin)

• cbg (corticosteroid binding globulin):

what does shbg carry ? (sex hormone binding globulin)

testosterone and estradiol

what does cbg carry? (corticosteroid binding globulin)

cortisol

aldosterone

progesterone

how do steroids enter cells?

by passive diffusion — they slip through the cell membrane because they’re lipophilic (fat-loving).

what happens once steroids are inside the cell?

they bind to receptors and change gene activity in the nucleus.

where are steroids mostly broken down?

in the liver.

why are steroids broken down?

to make them more water-soluble so the body can remove them.

what are the two phases of steroid metabolism?

phase i and phase ii

what happens in phase i of steroid metabolism

oxidation, reduction, or hydrolysis.

what happens in phase ii of steroid metabolism

adding polar groups like sulfate or glucuronic acid to increase solubility.

what is enterohepatic recycling?

when bile salts are reused between the intestine and liver to save cholesterol and aid digestion.

what are glucocorticoids used for in medicine?

to reduce inflammation and treat asthma, allergies, autoimmune diseases, and some cancers.

how do glucocorticoids fight inflammation?

transactivation,transrepression

what does transactivation do

turns on anti-inflammatory genes

what does transrepression

turns on anti-inflammatory genes.

what are common side effects of glucocorticoids?

weight gain, weak bones, high blood sugar, mood changes, and lower immunity.

why do these side effects happen?

because glucocorticoids affect many body systems, not just inflammation.

what is the negative feedback loop for glucocorticoids?

high cortisol levels stop the brain (hypothalamus and pituitary) from making more acth and crf, which reduces cortisol production.

what are synthetic corticosteroids?

man-made versions of natural corticosteroids, designed to be stronger or longer-lasting.

what are synthetic progestins?

modified forms of progesterone used in birth control

how do progestins work?

they prevent ovulation and make it harder for sperm to reach an egg.

what are synthetic estrogens?

modified versions of oestrogens like ethinylestradiol and mestranol used in contraceptives and hormone therapy.

how does the combined oral contraceptive pill (cocp) work?

it contains estrogen and progestin that prevent ovulation but allow normal menstruation during breaks.

what is the mini-pill (progesterone-only pill)?

it contains only progestin and thickens cervical mucus to block sperm and prevent implantation.