Endocrinology Made Simple : Bone mineral density, T score and Z scores

Bone mineral density, T  score and Z scores

T score is the Bone mineral density BMD of a patient in comparison to young healthy adults around 25 – 30 years of age.

The Z score is the BMD  score of a patient in comparison to age matched normal controls.

The BMD is categorized according to T score as below according to WHO CRITERIA FOR

POSTMENOPAUSAL CAUCASIAM WOMEN :

Normal T score > 1

Osteopenic  T score between – 1.0 and 2.5

Osteoporosis T score of less than – 2.5

As T score decreases,the risk of fracture increases without any threshold effect.

The diagnosis of osteoporosis in men and young premenopausal females by bone densitometry is not clear.

Apart from measuring BMD,some basic workup is needed to rule out secondary causes of osteoporosis.

This includes :

Full / complete blood count.

Routine chemistry profile : Serum calcium and phosphorus levels.

Urinary calcium

Serum protein electrophoresis

PTH

TSH

Bone turnover markers such as N tekopeptide for bone resorption and alkaline phosphatase for bone

formation.