Immunoglobulin A and Testosterone in Women: Physiological Roles and Clinical Significance
Immunoglobulin A (IgA) in Women
IgA serves as the most abundant antibody class in the body, providing critical immune defense at mucosal surfaces and in secretions including breast milk, where it protects both the mother and nursing infant. 1, 2
Primary Functions of IgA
IgA represents the first line of defense at mucosal surfaces of the gastrointestinal, respiratory, and genitourinary tracts, neutralizing pathogens before they can invade tissues 2, 3
More IgA is produced than all other immunoglobulin classes combined, underscoring its critical importance in immune surveillance 4
IgA exists in two forms: monomeric IgA in serum and polymeric (mainly dimeric) secretory IgA at mucosal surfaces, each with distinct protective functions 2, 4
IgA in Maternal-Infant Protection
Secretory IgA (sIgA) is the dominant immunoglobulin in breast milk, comprising 88-90% of total immunoglobulins and providing passive immunity to nursing infants 1
Dimeric IgA molecules attach to polymeric Ig-receptors on mammary gland epithelium, undergo transcytosis through epithelial cells, and are released into breast milk with the secretory chain attached 1
Colostrum contains the highest concentrations of sIgA, which decline in mature milk but remain stable within individual mothers from day 6 to at least day 90 postpartum 1
Clinical Implications of IgA Deficiency
Selective IgA deficiency is the most common primary immunodeficiency, and affected individuals may develop antibodies to IgA that can cause anaphylactic reactions to blood products 1
Persons with IgA deficiency should not receive immune globulin products due to risk of severe anaphylactic reactions 1
IgA deficiency increases susceptibility to recurrent sinopulmonary infections and may be associated with autoimmune conditions 1
Testosterone in Women: Bioavailability and Clinical Context
Routine measurement of testosterone levels in women is not recommended in clinical practice, as there is no well-defined clinical syndrome of androgen deficiency or excess that warrants routine testing. 5
Physiological Role of Testosterone
Testosterone in women is produced primarily by the ovaries and adrenal glands, with smaller amounts from peripheral conversion of precursor hormones 1
Total testosterone or bioavailable/free testosterone measurements may be obtained when evaluating hyperandrogenism in conditions like polycystic ovary syndrome (PCOS), where elevated androgens cause hirsutism, acne, and metabolic dysfunction 1
Immunological Effects of Testosterone
Testosterone inhibits immunoglobulin production by peripheral blood mononuclear cells in both males and females, with suppression of IgG by 59% and IgM by 61.3% at physiological concentrations 6
The immunosuppressive effect occurs through two mechanisms: direct inhibition of B cell activity and indirect suppression via reduced IL-6 production by monocytes 6
This immunomodulatory property suggests testosterone may have protective effects against autoimmune diseases, which are more prevalent in women who have lower testosterone levels than men 6
Clinical Testing Considerations
When hyperandrogenism is suspected clinically (hirsutism, acne, menstrual irregularities), measurement of total testosterone or bioavailable testosterone is appropriate to evaluate for ovarian hyperandrogenism 1
Sex hormone binding globulin (SHBG) levels are decreased in conditions with hyperinsulinemia and obesity, which increases bioavailable testosterone and contributes to clinical manifestations 1
Integration: Why Both Are Measured
The bioavailability of both IgA and testosterone in women reflects distinct but clinically important physiological systems:
IgA bioavailability is measured to assess immune competence, particularly when evaluating recurrent infections, suspected immunodeficiency, or before administering blood products 1
Testosterone bioavailability is assessed when clinical signs suggest androgen excess, particularly in reproductive-age women with PCOS or other hyperandrogenic conditions 1
These measurements address different clinical questions: IgA for immune function and infection risk, testosterone for reproductive/metabolic disorders and their associated cardiovascular risks 1