I’ve always thought it amazing how with just a piece of paper, pee and five minutes
I’ve always thought it amazing how with just a piece of paper, pee and five minutes

of your time you can find out whether you’re pregnant or not.
of your time you can find out whether you’re pregnant or not.

However, as simple as pregnancy tests are to use, they are actually a feat of biochemical
However, as simple as pregnancy tests are to use, they are actually a feat of biochemical

engineering, and today I’m going to tell you exactly how they work, and how they can
engineering, and today I’m going to tell you exactly how they work, and how they can

not only inform us about pregnancy, but they can also help us with the diagnosis of prenatal
not only inform us about pregnancy, but they can also help us with the diagnosis of prenatal

conditions and certain types of cancer!
conditions and certain types of cancer!

[Intro by Cristina de Manuel & Caro Waro] In Ancient Egypt, women used to pee on barley
[Intro by Cristina de Manuel & Caro Waro] In Ancient Egypt, women used to pee on barley

and wheat plants to find out if they were pregnant, and a few days later, if the plants
and wheat plants to find out if they were pregnant, and a few days later, if the plants

had grown, it was a sign that they were pregnant, and the plant that had grown the most would
had grown, it was a sign that they were pregnant, and the plant that had grown the most would

determine the sex of the future child.
determine the sex of the future child.

Now, whilst this may sound like a p1$$-take, the Egyptians were actually on the right track
Now, whilst this may sound like a p1$$-take, the Egyptians were actually on the right track

when using urine as a means for detecting pregnancy, and even more surprisingly, a modern
when using urine as a means for detecting pregnancy, and even more surprisingly, a modern

study showed that the plant growth was accurate in detecting pregnancy on 70% of the occasions.
study showed that the plant growth was accurate in detecting pregnancy on 70% of the occasions.

[Not so much so for detecting the sex of the future child mind you!]
[Not so much so for detecting the sex of the future child mind you!]

Now, the reason for this is that a hormone produced early on during pregnancy is capable
Now, the reason for this is that a hormone produced early on during pregnancy is capable

of stimulating growth in plants – and very conveniently, is excreted through our urine.
of stimulating growth in plants – and very conveniently, is excreted through our urine.

This hormone is the human chorionic gonadotropin hormone – or hCG for short.
This hormone is the human chorionic gonadotropin hormone – or hCG for short.

Our bodies produce very low levels of hCG, but after the implantation of a fertilised
Our bodies produce very low levels of hCG, but after the implantation of a fertilised

ovum in the placenta, the concentrations of hCG in a pregnant person’s body dramatically
ovum in the placenta, the concentrations of hCG in a pregnant person’s body dramatically

increases, and this hormone is crucial to signal to the body that it’s time to kickstart
increases, and this hormone is crucial to signal to the body that it’s time to kickstart

pregnancy.
pregnancy.

hCG is what is known as a heterodimeric glycoprotein.
hCG is what is known as a heterodimeric glycoprotein.

The glycoprotein bit means that it’s a protein with a carbohydrate group attached, and the
The glycoprotein bit means that it’s a protein with a carbohydrate group attached, and the

heterodimeric part means that it is formed of two different subunits, alpha and beta.
heterodimeric part means that it is formed of two different subunits, alpha and beta.

In hCG, the alpha subunit is common to all glycoproteins of the same family, including
In hCG, the alpha subunit is common to all glycoproteins of the same family, including

follicle-stimulating hormone, luteinising hormone and thyroid stimulating hormone – but
follicle-stimulating hormone, luteinising hormone and thyroid stimulating hormone – but

the beta subunit is unique to hCG – and that is precisely what the pregnancy test
the beta subunit is unique to hCG – and that is precisely what the pregnancy test

strips are designed to detect.
strips are designed to detect.

The way pregnancy tests do it is by using a so-called ELISA test, which stands for enzyme-linked
The way pregnancy tests do it is by using a so-called ELISA test, which stands for enzyme-linked

immunosorbent assay.
immunosorbent assay.

Its job is to detect a particular substance within a particular liquid, and in this case,
Its job is to detect a particular substance within a particular liquid, and in this case,

the substance is the unique beta unit from hCG, and the liquid is urine, and it’s a
the substance is the unique beta unit from hCG, and the liquid is urine, and it’s a

sandwich because said liquid must pass through three zones lined with antibodies, with the
sandwich because said liquid must pass through three zones lined with antibodies, with the

important test happening in the middle.
important test happening in the middle.

Antibodies are very special biological chemicals, made up of a constant zone, and a specific
Antibodies are very special biological chemicals, made up of a constant zone, and a specific

zone, which is designed to bind to specific compounds.
zone, which is designed to bind to specific compounds.

The first zone is the reaction zone.
The first zone is the reaction zone.

It is lined with antibodies that can bind with hCG.
It is lined with antibodies that can bind with hCG.

As the urine passes through, these are swept up, and if hCG is present, the antibodies
As the urine passes through, these are swept up, and if hCG is present, the antibodies

will bind to it.
will bind to it.

The second test zone is lined with antibodies that detect antibodies that are bound to hCG.
The second test zone is lined with antibodies that detect antibodies that are bound to hCG.

These are picked up and cause dye release, which is the positive pregnancy test line
These are picked up and cause dye release, which is the positive pregnancy test line

that can be both exciting and terrifying for many!
that can be both exciting and terrifying for many!

The final test zone is the control zone, this one simply detects the constant zone of the
The final test zone is the control zone, this one simply detects the constant zone of the

passing antibodies to ensure the test has run correctly, and as they detect the antibodies
passing antibodies to ensure the test has run correctly, and as they detect the antibodies

from the reaction zone passing through, they release dye.
from the reaction zone passing through, they release dye.

This line basically tells us that the test has run correctly.
This line basically tells us that the test has run correctly.

Now, so far I’ve spoken about urine tests, which are your traditional over the counter
Now, so far I’ve spoken about urine tests, which are your traditional over the counter

tests.
tests.

However there are also serum tests which take blood, and they can detect even lower concentrations
However there are also serum tests which take blood, and they can detect even lower concentrations

of hCG, and unlike urine tests which are generally qualitative tests, serum tests can quantify
of hCG, and unlike urine tests which are generally qualitative tests, serum tests can quantify

the levels of hCG.
the levels of hCG.

There are various reasons that you may want to do that.
There are various reasons that you may want to do that.

For one, it can actually tell you exactly when conception happened, but they are informative
For one, it can actually tell you exactly when conception happened, but they are informative

in other contexts as well.
in other contexts as well.

For instance, some studies have found links between persistently high levels of hCG in
For instance, some studies have found links between persistently high levels of hCG in

the first trimester and Down syndrome.
the first trimester and Down syndrome.

hCG tests are also helpful for detecting and monitoring ectopic pregnancies and miscarriages
hCG tests are also helpful for detecting and monitoring ectopic pregnancies and miscarriages

and high hCG levels can also be a sign of certain types of tumours and cancer, such
and high hCG levels can also be a sign of certain types of tumours and cancer, such

as pituitary gland cancers or testicular cancers, and measuring hormone levels is a very safe
as pituitary gland cancers or testicular cancers, and measuring hormone levels is a very safe

and non-invasive way to monitor them.
and non-invasive way to monitor them.

Finally, hCG tests can also be used in anti-doping contexts, as some male athletes may use hCG
Finally, hCG tests can also be used in anti-doping contexts, as some male athletes may use hCG

to stimulate testosterone production due to its similarity to luteinising hormone.
to stimulate testosterone production due to its similarity to luteinising hormone.

So without a doubt – how much a simple hormone can tell us about the inner workings of our
So without a doubt – how much a simple hormone can tell us about the inner workings of our

bodies can be both relieving and mind-boggling – and it’s all thanks to biochemistry!
bodies can be both relieving and mind-boggling – and it’s all thanks to biochemistry!

And hey!
And hey!

In the time it’s taken me to tell you all of this – my test is ready to interpret!
In the time it’s taken me to tell you all of this – my test is ready to interpret!

Negative!
Negative!

I really hope you enjoyed today's episode - this was actually my entry to the Biochemical
I really hope you enjoyed today's episode - this was actually my entry to the Biochemical

Society's Science Communication Competition back in April aaaand it came in third place
Society's Science Communication Competition back in April aaaand it came in third place

- so I hope you enjoyed it.
- so I hope you enjoyed it.

if you want to see the first and second entries and I think a few written entries as well,
if you want to see the first and second entries and I think a few written entries as well,

I will link those down below - and as always, thank you so much for watching me and I'll
I will link those down below - and as always, thank you so much for watching me and I'll

see you in the next one!
see you in the next one!

Bye!
Bye!

[Music: Thastor & CryoSleepKitten] [Art & Animation: Caro Waro & Cristina de
[Music: Thastor & CryoSleepKitten] [Art & Animation: Caro Waro & Cristina de

Manuel] [Hosting, Scripting, Editing: Inés Dawson]
Manuel] [Hosting, Scripting, Editing: Inés Dawson]

[Translated by {your name} into {language}]
[Translated by {your name} into {language}]