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T- versus Z-score
megmo84 posted:
A little clarification, please... At what age or point is the T-score used instead of a Z-score?
Byroney_WebMD_Staff responded:
Dear megmo84,

This article on Bone Scans and Bone Screenings may help answer your question.

"The T-score is a comparison of a person's bone density with that of a healthy 30-year-old of the same sex.

The Z-score is a comparison of a person's bone density with that of an average person of the same age and sex."

One of our Health Experts from the NOF or our members may reply, too. However, be sure to ask your doctor for an expert opinion based on you and your medical history.

Yours in health,

Susan Allison, RNC, BSN, MPA responded:
Dear megmo84,

A Z-score compares your bone density to what is normal for someone your age. While a Z-score alone is not used to diagnose osteoporosis in premenopausal women, it can provide important information. Here are some tips to help you understand your Z-score:

*If your Z-score is above -2.0, your bone density is considered within the ranges expected for your age or normal according to the International Society for Clinical Densitometry (ISCD). For example, a Z-score of 0.5, -0.5 and -1.5 is considered normal for most premenopausal women.

*If your Z-score is -2.0 or lower, your bone density is considered below the expected range. Examples are -2.1, -2.3 and -2.5. If your Z-score is in this range, your healthcare provider will consider your health history and possible causes of bone loss, including secondary osteoporosis, before making a diagnosis of osteoporosis.

*If your Z-score is normal, but you've broken one or more bones from a minor injury, your healthcare provider may diagnose you with osteoporosis because some people with normal bone density break bones easily. As mentioned above, a bone density test will also show a T-score. A T-score compares bone density to what is normal in a healthy 30-year-old adult.
megmo84 replied to Susan Allison, RNC, BSN, MPA's response:
So as a 26-year-old, the Z-score is more relevant to my situation. Correct?
bonebabe replied to megmo84's response:
Only if you're a premenopausal 26 year old. Z-scores are used only on premenopausal women and on men younger than 50.
megmo84 replied to bonebabe's response:
Bonebabe -

In a different post your remarked that young women in their twenties and thirties are considered postmenopausal if they've been amenorrheic for over a year. True? What about those of us who get periods by artificial means such as birth control?
bonebabe replied to megmo84's response:
No, I don't believe that exactly what I said because I don't know that that's true for young women as there are treatments available to restart their periods. Women who have functioning ovaries will go through a perimenopausal stage where their periods get out of whack - they may skip months, have very light months or extremely heavy. This is because the estrogen is shutting down and going haywire. After you've been one year without any kind of period, you are considered to be postmenopausal.
Tomato05 replied to bonebabe's response:
The whole pre- and post-menopause is a bit of a grey area.

My periods "vanished" when I was 32 after I stopped the birth control pill. Yet, my hormone levels indicated that I was still pre-menopausal.

The periods stayed away for about 13 years (resurfaced last year again, when I was 45!). Nobody could ever tell me why.

I was diagnosed with osteoporosis (officially) when I was 35 and started taking Fosamax then.

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