Insight into your PTH level.
PTH is the hormone of the parathyroid glands and, together with vitamin D, regulates calcium in your blood, bones and kidneys. The result is nearly always assessed alongside calcium, because the two can only be read in context.
Also known as: Parathyroid hormone, iPTH
Personal assessment by our BIG-registered doctors
By the Bloodworks editorial team
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Background
What is PTH?
PTH, or parathyroid hormone, is produced by the parathyroid glands: four glands the size of a grain of rice that sit behind the thyroid. They continuously sense how much calcium is in your blood. When calcium falls they release more PTH, and when calcium rises they release less. PTH acts through the bones, where calcium is released, and through the kidneys, where less calcium is lost in the urine and where vitamin D is converted into its active form. That active form in turn governs how much calcium you absorb from food.
Because of that feedback loop, PTH is almost never read on its own. The value only takes on meaning next to the calcium level from the same blood draw, since the same PTH result means something different with a high calcium than with a low one. Two well-known reasons for a rising PTH are a vitamin D deficiency and reduced kidney function. There is also a practical point: PTH follows a daily rhythm and fluctuates over the course of the day, so a morning blood draw gives the most comparable result.
In brief
Parathyroid glands
Four small glands behind the thyroid produce this hormone
Always with calcium
PTH and calcium can only be read in context with each other
Vitamin D
Works together with PTH in calcium balance
Daily rhythm
The level fluctuates over the day, a morning blood draw is preferred
Common reasons to test
When can insight into your PTH be valuable?
Below are some situations in which measuring PTH can provide insight.
Insight into your calcium regulation
A measurement shows how hard the parathyroid glands are working to keep the calcium in your blood steady.
Always together with calcium
PTH and calcium steer one another. Include both tests in the same blood draw, otherwise the result cannot be placed properly.
After an abnormal calcium result
If your calcium previously fell outside the reference values stated by the laboratory, PTH is the usual addition to complete the picture.
With a vitamin D deficiency
A low vitamin D is a known reason for PTH to rise. Measuring both lets you see the values side by side instead of in isolation.
With reduced kidney function
The kidneys play a central role in calcium balance. When they work less well, a rise in PTH is a familiar pattern.
A morning blood draw
PTH follows a daily rhythm. A blood draw in the morning gives the most comparable result, also when you measure again later.
Following up an earlier result
If you want to follow up an earlier PTH result, book another morning appointment and include calcium in the same draw.
What your result means
How do we read your PTH level?
PTH is measured in picomoles per litre (pmol/L), sometimes in nanograms per litre (ng/L). The laboratory states the reference values that apply there alongside your result, and those are leading. Important: PTH cannot be interpreted on its own. The same PTH value means something different with a high calcium than with a low one, which is why our doctor always assesses the two together.
A low value
A low PTH means the parathyroid glands are releasing little hormone at that moment. What fits with that depends on the calcium level from the same blood draw. A generous intake of calcium or vitamin D from supplements also plays a part in the picture. Our doctor looks at the whole picture rather than this number alone.
A value within the reference range
A PTH within the laboratory's reference values gives a reassuring picture for this marker, certainly when your calcium falls within them too. A single measurement remains a snapshot and is not a diagnosis.
An elevated value
An elevated PTH means the parathyroid glands are working harder. That regularly occurs with a vitamin D deficiency or with reduced kidney function, where the calcium in the blood often still holds steady. If calcium is raised as well, a different follow-up applies. Which situation it is only becomes clear by reading PTH and calcium together. Our doctor will discuss what the combination means in your situation and whether further testing is customary.
How we interpret your result
Related tests
Often combined with PTH.
A single marker gives one perspective. For a broader picture you can combine PTH with a theme package or related markers.
+ €29 blood draw fee per orderFree from €225
Frequently asked questions
Everything you want to know
Do I need to fast for a PTH test?
Fasting is not necessary for PTH. A blood draw in the morning is preferred, because PTH follows a daily rhythm and fluctuates over the day. If you combine the test with glucose or cholesterol, for example, the fasting instructions do apply to those tests.
Why should I have calcium measured as well?
PTH and calcium steer one another: the parathyroid glands respond to the calcium level in your blood. A PTH result without calcium from the same draw therefore cannot be placed, because the same number fits with very different situations. We advise ordering the two tests together.
What exactly do the parathyroid glands do?
The parathyroid glands are four small glands behind the thyroid. They keep the calcium level in your blood within narrow limits by releasing more or less PTH. Despite the name, their task differs from that of the thyroid itself, which mainly drives your metabolism.
Why can a vitamin D deficiency raise my PTH?
Vitamin D helps your body absorb calcium from food. With little vitamin D, less calcium comes in and the parathyroid glands work harder to keep the calcium level in the blood steady. An elevated PTH alongside a low vitamin D is therefore a familiar pattern. Our doctor assesses whether that applies in your situation.
What does my kidney function have to do with PTH?
The kidneys retain calcium and convert vitamin D into its active form. With reduced kidney function that works less well, which can push PTH up. That is why kidney function is often looked at alongside an elevated PTH, for example with creatinine and eGFR.
When is the best time to have blood drawn?
In the morning. PTH follows a daily rhythm, so two measurements taken at different times of day are hard to compare. If you book a follow-up around the same time of day, the difference between the two results tells you more.
Can I order PTH on its own?
You can, but it adds little. Without calcium from the same blood draw the result is hard to interpret. If you want more context, vitamin D and kidney function are the logical additions, because both influence the PTH level.
What happens if my level is abnormal?
You receive your result with a personal explanation from our doctor, who explains what the combination of PTH and calcium means in your situation and whether further testing is worthwhile. If you have symptoms, your GP remains the right starting point, because an assessment involves more than blood alone.
Ready for insight into your PTH level?
You receive your PTH level including a personal explanation from a doctor, usually within 2 working days. No referral needed.
Order PTH →Want to test multiple markers at once?
Combine PTH with other markers via Bloodworks Select. The blood draw and collection fee is charged once per order, and is waived from €225.
45,-
+ €29 blood draw fee+ €29 blood draw fee per order