Figure 1. The pattern of MIS in human serum is sexually dimorphic and varies with age.
MIS in males is high at birth and, after a transient drop at approximately 2 years of age, levels are maintained until puberty. Serum MIS in females becomes measurable in the prepubertal period and is sustained until the menopause, after which it is no longer produced. The shaded bar demonstrates why serum MIS is useful in the perinatal period for evaluating cases of ambiguous genitalia. MIS is absent in genetic females and positive in cases with testicular tissue. The higher the values, the more normal the tissue. Serum testosterone is undetectable in normal males at this time. Rising serum MIS over normal limits in adult females (dotted line) is consistent with granulosa or sex cord tumors. MIS: Müllerian Inhibiting Substance.