Prenatal Androgen and Skills

Official title

Prenatal Androgen and Fine Motor Skills and Tactile Discrimination

Overview

Due to the difficulties and risks of directly measuring prenatal hormone levels, biomarkers that indirectly reflect this exposure are used in research. In this context, the ratio of second to fourth finger length (2D:4D) is widely preferred because it is an easily applicable and non-invasive measurement. Evidence shows that 2D:4D stabilizes from the second trimester of pregnancy onward and exhibits strong sex differences across populations. The 2D:4D ratio is generally lower in men than in women. 2D is more strongly influenced by prenatal estrogen, while 4D is more strongly influenced by prenatal testosterone; this occurs during the first trimester of intrauterine fetal development. To our knowledge, studies examining the relationship between the 2D:4D ratio, an indirect indicator of prenatal androgen exposure, and dexterity and tactile discrimination are limited. Accordingly, the planned study aims to evaluate the relationship between the 2D:4D ratio and fine motor skills and tactile discrimination in healthy young adults.

Detailed description

Sex hormones experienced during prenatal exposure play a significant role in shaping certain lifelong characteristics by influencing both the physical and neurological development of individuals. The effects of these hormones, particularly on the developing nervous system, contribute to the emergence of behavioral and functional differences. Hand preference and certain behavioral traits in humans have been shown to be related to prenatal hormonal exposure. However, the development of these traits is not limited to hormonal influences alone, but is shaped by the interaction of genetic, environmental, and sociocultural factors. Due to the difficulties and risks of directly measuring prenatal hormone levels, biomarkers that indirectly reflect this exposure are used in research. In this context, the ratio of second to fourth finger length (2D:4D) is widely preferred because it is an easily applicable and non-invasive measurement. The 2D:4D ratio is generally lower in men than in women. 2D is more strongly influenced by prenatal estrogen, while 4D is more strongly influenced by prenatal testosterone; this occurs during the first trimester of intrauterine fetal development. However, whether the 2D:4D ratio is a reliable indicator of prenatal hormonal exposure is still a controversial issue in the literature. Therefore, examining the relationship between the 2D:4D ratio and various biological and functional characteristics remains important. To our knowledge, studies examining the relationship between the 2D:4D ratio, an indirect indicator of prenatal androgen exposure, and dexterity and tactile discrimination are limited. Accordingly, the planned study aims to evaluate the relationship between the 2D:4D ratio and fine motor skills and tactile discrimination in healthy young adults. It is hypothesized that prenatal hormonal exposure may indirectly shape finger morphology and receptor distribution by affecting skin and nervous system development, which may be a determining factor in tactile sensitivity and dexterity.

Interventions

• Other Digit Ratio
  The second (2D) and fourth (4D) finger lengths of the participants will be measured separately in both hands by a physiotherapist with over thirteen years of clinical experience.
• Behavioral Fine motor skills
  Hand dexterity will be assessed using the Purdue Pegboard Test. The test will be administered according to standard procedure with participants seated at a table. Participants will be asked to place the pegs into the corresponding holes as quickly and accurately as possible within a specified time (30 seconds).
• Behavioral Tactile Discrimination
  To perform the 2-point discrimination tests, the Baseline® two-point discriminator will be used. Measurements will be applied to the distal phalangeal pulp of the index finger on both hands while participants are seated in a comfortable position with their eyes closed.

Primary outcome measures

• 2-point discrimination test [Time frame: 12 months]
• Digit Ratio [Time frame: 12 months]
• Fine motor skills [Time frame: 12 months]

Eligibility criteria

Inclusion criteria

• Healthy individuals aged 18-40
• Having sufficient visual and auditory function to understand and administer the test,
• Voluntary agreement to participate in the study and providing informed consent.

Exclusion criteria

• Individuals with any musculoskeletal pathology,
• History of upper extremity trauma,
• Individuals diagnosed with metabolic, neurological, or genetic diseases,
• Individuals with a history of hand surgery within the last 6 months,
• Pregnancy or breastfeeding.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Observational model

Other

Study locations

Turkey (Türkiye) · 1 center

• Nigde Omer Halisdemir University — Niğde

Publications

• Butovskaya M, Adam Y, Batsevich V, Shackelford TK, Fink B. Associations between 2D:4D from direct and radiographic measurements with handgrip strength in young adult Tuvans. Early Hum Dev. 2024 Jun;193:106037. doi: 10.1016/j.earlhumdev.2024.106037. Epub 2024 May 8. PMID 38743999
• Fink B, Manning JT, Neave N, Tan U. Second to fourth digit ratio and hand skill in Austrian children. Biol Psychol. 2004 Nov;67(3):375-84. doi: 10.1016/j.biopsycho.2004.03.012. PMID 15294393

Identifiers

NCT: NCT07627113 · Androgen and Skills

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗