Question 1

What is the Meaning of FAI?

Accepted Answer

FAI is a calculated ratio estimating bioavailable testosterone, specifically the fraction not bound to sex hormone-binding globulin (SHBG). This index offers a more accurate assessment of androgen activity than total testosterone alone, as SHBG's significant binding capacity renders much circulating testosterone biologically inactive.

Question 2

What is the Context of FAI?

Accepted Answer

Within human endocrinology, the Free Androgen Index serves as a critical marker evaluating the dynamic interplay between circulating androgens and SHBG. This index is relevant within the hypothalamic-pituitary-gonadal axis, where testosterone exerts physiological effects. SHBG, primarily hepatic, modulates androgen availability by binding to testosterone, influencing biological impact.

Question 3

What is the Significance of FAI?

Accepted Answer

The Free Androgen Index holds significant clinical importance in diagnosing androgen excess or deficiency. For women, elevated FAI often indicates hyperandrogenism, seen in polycystic ovary syndrome (PCOS), manifesting as hirsutism or menstrual irregularities. In men, a low FAI might suggest androgen deficiency, even with normal total testosterone, contributing to reduced libido or fatigue. It distinguishes true androgenic activity.

Question 4

What is the Mechanism of FAI?

Accepted Answer

The Free Androgen Index is derived from a mathematical calculation: (Total Testosterone / SHBG) 100. This formula approximates the testosterone fraction not bound to SHBG, considered biologically active and interacting with androgen receptors. While albumin also binds testosterone, its lower affinity makes the SHBG-bound fraction the primary determinant of bioavailable testosterone.

Question 5

What is the Application of FAI?

Accepted Answer

Clinicians frequently utilize the Free Androgen Index in diagnostic workups for hormonal imbalances. For individuals with symptoms of androgen excess or deficiency, FAI provides nuanced understanding beyond total testosterone. It guides therapeutic decisions, particularly in managing PCOS or hypogonadism, allowing targeted interventions to restore hormonal equilibrium and alleviate symptoms. Monitoring FAI can also assess treatment efficacy.

Question 6

What is the Metric of FAI?

Accepted Answer

Assessment of the Free Androgen Index requires specific laboratory measurements: serum total testosterone and serum sex hormone-binding globulin (SHBG). These values are obtained through standard blood tests. Once quantitative measurements are available, the FAI is calculated using the established formula, providing a numerical representation of free androgen status. Reference ranges for FAI vary by laboratory.

Question 7

What is the Risk of FAI?

Accepted Answer

Misinterpretation or improper reliance on the Free Androgen Index without full clinical context can lead to diagnostic errors or inappropriate treatment. Factors like obesity, thyroid dysfunction, liver disease, and certain medications significantly influence SHBG levels, altering FAI independent of true androgenic status. Sole reliance on FAI without thorough patient evaluation may result in misdiagnosis or ineffective interventions, delaying appropriate care.

FAI

Meaning

Context

Significance

Mechanism

Application

Metric

Risk

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