Prenatal Hormonal Markers and Sleep Characteristics in Young Adults With Joint Hypermobility

Joint hypermobility is a clinical condition characterized by joints having a range of motion beyond their normal limits. Hormonal factors are thought to play a role in the development of joint hypermobility. One of the most significant indicators of prenatal androgen exposure is considered the ratio of the lengths of the second and fourth fingers (2D:4D). The 2D:4D digit ratio refers to the ratio of the lengths of the second finger (2D; index digit ) and the fourth finger (4D; ring digit). Evidence suggests that the 2D:4D ratio is developmentally stable and stabilizes from the second trimester of pregnancy onward. To our knowledge, intrauterine androgen exposure (2D:4D) has not been examined in populations with joint hypermobility. Therefore, the planned study aimed to examine the 2D:4D digit ratio in young adults with joint hypermobility and compare it with that of individuals without joint hypermobility.

Estrogen affects collagen metabolism and connective tissue structure, which can lead to increased ligament laxity at high levels. Increased estrogen and progesterone during pregnancy cause significant loosening of connective tissue, which can contribute to temporary joint hypermobility. Physiological conditions such as pregnancy and menopause can cause hormonal changes, increasing the risk of joint hypermobility through fluid retention and connective tissue changes. Testosterone, on the other hand, is a hormone that strengthens muscle mass and tendon structure, while at low levels it can cause connective tissue to remain looser. Therefore, the combination of high estrogen and relatively low testosterone, particularly in women of reproductive age, may contribute to the higher prevalence of hypermobility. Therefore, the aim of the planned study was to examine the 2D:4D digit ratio in young adults with joint hypermobility and compare this ratio with individuals without joint hypermobility.