0:00:07.146,0:00:10.836
Steroids: they’re infamous [br]for their use in sports.

0:00:10.836,0:00:15.747
But they’re also found in inhalers, [br]creams to treat poison ivy and eczema,

0:00:15.747,0:00:18.337
and shots to ease inflammation.

0:00:18.337,0:00:23.400
The steroids in these medicines aren’t [br]the same as the ones used to build muscle.

0:00:23.400,0:00:27.190
In fact, they’re all based on [br]yet another steroid—

0:00:27.190,0:00:31.640
one our body produces naturally, [br]and we can’t live without.

0:00:31.640,0:00:35.339
Taking a step back, the reason [br]there are so many different steroids

0:00:35.339,0:00:39.941
is because the term refers to substances [br]with a shared molecular structure,

0:00:39.941,0:00:42.881
rather than shared effects on the body.

0:00:42.881,0:00:45.750
Steroids can be naturally occurring [br]or synthetic,

0:00:45.750,0:00:49.900
but what all steroids have in common [br]is a molecular structure

0:00:49.900,0:00:54.970
that consists of a base of four rings [br]made of 17 carbon atoms

0:00:54.970,0:00:59.050
arranged in three hexagons [br]and one pentagon.

0:00:59.050,0:01:03.683
A molecule must contain [br]this exact arrangement to be a steroid,

0:01:03.683,0:01:06.753
though most also have side chains—

0:01:06.753,0:01:12.079
additional atoms that can dramatically [br]impact the molecule’s function.

0:01:12.079,0:01:16.039
Steroids get their name [br]from the fatty molecule cholesterol.

0:01:16.039,0:01:20.032
In fact, our bodies make steroids [br]out of cholesterol.

0:01:20.032,0:01:23.242
That fatty cholesterol base [br]means that steroids

0:01:23.242,0:01:27.602
are able to cross fatty cell membranes [br]and enter cells.

0:01:27.602,0:01:31.422
Within the cell, they can directly [br]influence gene expression

0:01:31.422,0:01:33.789
and protein synthesis.

0:01:33.789,0:01:37.399
This is different from many other types [br]of signaling molecules,

0:01:37.399,0:01:39.469
which can’t cross the cell membrane

0:01:39.469,0:01:42.859
and have to create their effects [br]from outside the cell,

0:01:42.859,0:01:45.628
through more complicated pathways.

0:01:45.628,0:01:51.185
So steroids can create their effects [br]faster than those other molecules.

0:01:51.185,0:01:55.065
Back to the steroids [br]in anti-inflammatory medications:

0:01:55.065,0:02:00.025
all of these are based on a naturally [br]occurring steroid called cortisol.

0:02:00.025,0:02:03.265
Cortisol is the body’s [br]primary stress signal,

0:02:03.265,0:02:05.809
and it has a huge range of functions.

0:02:05.809,0:02:07.959
When we experience a stressor—

0:02:07.959,0:02:11.209
anything from a fight with a friend, [br]to spotting a bear,

0:02:11.209,0:02:13.942
to an infection or low blood sugar—

0:02:13.942,0:02:19.935
the brain reacts by sending a signal from [br]the hypothalamus to the pituitary gland.

0:02:19.935,0:02:24.477
The pituitary gland then sends a signal [br]to the adrenal glands.

0:02:24.477,0:02:28.951
The adrenal glands produce cortisol, [br]and release some constantly.

0:02:28.951,0:02:32.521
But when they receive the signal [br]from the pituitary gland,

0:02:32.521,0:02:34.842
they release a burst of cortisol,

0:02:34.842,0:02:38.462
which spurs the body to generate [br]more glucose for energy,

0:02:38.462,0:02:42.882
decrease functions not immediately [br]related to survival, like digestion,

0:02:42.882,0:02:46.763
and can activate [br]a fight-flight-or-freeze response.

0:02:46.763,0:02:51.032
This is helpful in the short term, [br]but can cause undesirable side effects

0:02:51.032,0:02:55.299
like insomnia and lowered mood [br]if they last too long.

0:02:55.299,0:02:59.675
Cortisol also interacts [br]with the immune system in complex ways—

0:02:59.675,0:03:01.012
depending on the situation,

0:03:01.012,0:03:04.779
it can increase or decrease [br]certain immune functions.

0:03:04.779,0:03:06.769
In the process of fighting infection,

0:03:06.769,0:03:09.929
the immune system [br]often creates inflammation.

0:03:09.929,0:03:14.179
Cortisol suppresses the immune system’s [br]ability to produce inflammation,

0:03:14.179,0:03:17.335
which, again, [br]can be useful in the short term.

0:03:17.335,0:03:20.349
But too much cortisol [br]can have negative impacts,

0:03:20.349,0:03:25.988
like reducing the immune system’s ability [br]to regenerate bone marrow and lymph nodes.

0:03:25.988,0:03:29.138
To prevent levels [br]from staying high for too long,

0:03:29.138,0:03:32.935
cortisol suppresses the signal [br]that causes the adrenal glands

0:03:32.935,0:03:35.135
to release more cortisol.

0:03:35.135,0:03:39.828
Medicinal corticosteroids channel [br]cortisol’s effects on the immune system

0:03:39.828,0:03:44.008
to fight allergic reactions, [br]rashes, and asthma.

0:03:44.008,0:03:46.844
All these things are forms [br]of inflammation.

0:03:46.844,0:03:50.915
There are many synthetic steroids [br]that share the same basic mechanism:

0:03:50.915,0:03:53.405
they enhance the body’s cortisol supply,

0:03:53.405,0:03:56.908
which in turn shuts down [br]the hyperactive immune responses

0:03:56.908,0:03:59.095
that cause inflammation.

0:03:59.095,0:04:04.041
These corticosteroids sneak into cells [br]and can turn off the “fire alarm”

0:04:04.041,0:04:08.889
by suppressing gene expression [br]of inflammatory signals.

0:04:08.889,0:04:13.914
The steroids in inhalers and creams impact[br]only the affected organ—

0:04:13.914,0:04:16.124
the skin, or the lungs.

0:04:16.124,0:04:20.885
Intravenous or oral versions, used [br]to treat chronic autoimmune conditions

0:04:20.885,0:04:26.317
like lupus or inflammatory bowel disease, [br]impact the whole body.

0:04:26.317,0:04:30.740
With these conditions, the body’s [br]immune system attacks its own cells,

0:04:30.740,0:04:35.419
a process analogous to a constant [br]asthma attack or rash.

0:04:35.419,0:04:37.769
A constant low dose of steroids

0:04:37.769,0:04:41.648
can help keep this renegade[br]immune response under control—

0:04:41.648,0:04:45.258
but because of the negative psychological [br]and physiological effects

0:04:45.258,0:04:46.704
of longterm exposure,

0:04:46.704,0:04:51.488
higher doses are reserved [br]for emergencies and flare-ups.

0:04:51.488,0:04:55.498
While an asthma attack, poison ivy welts, [br]and irritable bowel syndrome

0:04:55.498,0:04:59.582
might seem totally unrelated, [br]they all have something in common:

0:04:59.582,0:05:03.790
an immune response [br]that’s doing more harm than good.

0:05:03.790,0:05:07.091
And while corticosteroids [br]won’t give you giant muscles,

0:05:07.091,0:05:10.624
they can be the body’s best defense [br]against itself.