Intrauterine hormone effects on tooth dimensions

Excerpt

Tooth dimension is influenced by genetic, epigenetic, and environmental factors. Sexual dimorphism is claimed to be influenced by growth-promoting effects of the Y chromosome. Intrauterine hormonal influences during tooth development also seem to play a major role. The testicular differentiation in the male happens around week 6 of gestation, initiated by the SRY gene on the Y chromosome. The levels of testosterone during gestation have been examined by amniocentesis. We know that soon after testicular differentiation (at around 7–9 weeks of gestation) there is a surge of testosterone with its highest levels occurring between weeks 10 and 24 in utero. During late gestation, the testosterone levels must be higher in males than females, as higher levels have been found at birth in umbilical cord blood. Although amniocentesis provides the most accurate measurement of fetal testosterone levels, it is invasive. An alternative approach is the use of the Twin Transfer Testosterone Hypothesis (TTTH), which is based on studies demonstrating that androgens can diffuse from a male to a female fetus, influencing behavioral and morphological traits. …