T Calc 2.3.1

The Free Testosterone and Bioavailable Testosterone Calculator application is intended to support healthcare professionals in accurately estimating circulating levels of bioactive testosterone. By simply entering the relevant laboratory values and activating the calculation, users can obtain rapid and precise results.

Application Usage Instructions for the Free & Bioavailable Testosterone Calculator

This calculator minimizes the potential for errors inherent in manual calculations by automating complex computations. To utilize the tool, input current laboratory data into designated fields for:

• Albumin
• Sex Hormone-Binding Globulin (SHBG)
• Total Testosterone

After entering the necessary values, press the calculate button to allow the app to perform the calculation automatically.

Understanding Free & Bioavailable Testosterone

Testosterone and dihydrotestosterone (DHT) are present in plasma either unbound (free, approximately 2-3%), bound to specific plasma proteins such as SHBG, or weakly bound to non-specific proteins like albumin. The fraction bound to SHBG is biologically inactive due to high binding affinity.

Bioavailable testosterone encompasses both the free and weakly bound forms, whereas free testosterone specifically refers to the unbound fraction.

Clinical conditions and medications—such as corticosteroids—can influence SHBG levels, thus affecting total serum testosterone measurements. A comprehensive assessment combining albumin, SHBG, and testosterone levels offers a more accurate reflection of a patient's testosterone status.

Reference Ranges for Free Testosterone

• Males (16 years and older): 9-30 ng/dL
• Females: 0.3–1.9 ng/dL

Reference Ranges for Bioavailable Testosterone

• Males:
  • 20-29 years: 83-257 ng/dL
  • 30-39 years: 72-235 ng/dL
  • 40-49 years: 61-213 ng/dL
  • 50-59 years: 50-190 ng/dL
  • 60-69 years: 40-168 ng/dL
  • >69 years: not established
• Females (non-oophorectomized):
  • 20-50 years (on oral estrogen): 0.8-4.0 ng/dL
  • 20-50 years (not on oral estrogen): 0.8-10 ng/dL
  • >50 years: not established

This application has been partially developed through an educational grant from Besins Healthcare (UK) Ltd., which has no editorial control over its content.

Important Limitations

This calculator serves as an educational aid and should not be solely relied upon for clinical decision-making. No guarantees are made regarding its accuracy or appropriateness for specific cases. Healthcare providers should always exercise their professional judgment and consult relevant guidelines before making clinical decisions.

Moreover, the calculated values of free and bioavailable testosterone may not be reliable in situations involving significant interference from steroids binding to SHBG—for example, in pregnant women or men undergoing treatments that increase DHT or Mesterolone levels.