Second to fourth digit ratio and prostate cancer severity

Systematical assessment of digit ratio in a female masculinization disease: polycystic ovary syndrome

Background

In recent years, the right ratio of 2nd and 4th digit length (2D:4D) is regarded as an anatomical marker of prenatal testosterone exposure. Polycystic ovary syndrome (PCOS) is a female masculinized disease and is determined by prenatal testosterone exposure. Whether the ratio in the right hand of PCOS women is reduced or not compared with non-PCOS women is under debate. To further investigate the relationship between PCOS and digit ratio, we systematically measured all the digit ratios.

Methods

We recruited 34 non-PCOS women, 116 PCOS women, and 40 men and systematically measured all the ratios of digit length (2D:3D, 2D:4D, 2D:5D, 3D:4D, 3D:5D, and 4D:5D) of right hands and left hands.

Results

Left 2D:3D, 2D:4D, and 2D:5D in men were significantly lower than those in non-PCOS women. Significantly lower digit ratios of left 2D:3D and 2D:4D were observed in PCOS compared with non-PCOS women. In the subgroup analysis, the left ratio of digit length in 2D:3D and 2D:5D of the hyperandrogenism subgroup was lower than that of the non-hyperandrogenism subgroup without statistical significance. The logistic regression model of PCOS revealed that 2D:3D, 2D:4D, 2D:5D, and 3D:4D of left hands were statistically related to the diagnosis of PCOS among all the digit ratios.

Conclusion

Not only 2D:4D but also other digit ratios, such as 2D:3D and 2D:5D, are a marker of prenatal testosterone exposure and may be an anatomical marker of PCOS. The majority of these significant differences included left 2D, with the following order: non-PCOS women > PCOS women > men.

Digital biomarker 2D:4D as a predictor of cancer: A systematic review

BACKGROUND

The digital ratio between the second and fourth digits of the hands, known as 2D:4D, is sexually dimorphic. It has been suggested that a low 2D:4D indicates high exposure to prenatal testosterone and low estrogen exposure while a high 2D:4D indicates the inverse. The 2D:4D may be predictive of cancer susceptibility, and this may be particularly true in cancers that show differences between sexes in their occurrence.

AIM

To conduct a systematic review of published epidemiological literature examining the association between 2D:4D and cancer.

METHOD

This review was carried out according to criteria recommended for the systematic review of Statement PRISMA. We enrolled 25 papers involving eleven cancer topographies with 4,569 cases and 19,416 controls from Europe, America, Asia and Australia.

RESULTS

We noticed variations and discrepancies in the results of the association between 2D:4D and cancer among the studies, either in those that had evaluated the same or different types of cancer, or in the same or distinct lateralities. However, a high 2D:4D was considered a likely predictor of cancer risk in 11 of 25 studies, a low 2D:4D was suggested as a predictor of risk in eight papers, and five of the twenty-five studies did not demonstrate any association.

CONCLUSIONS

Although this biomarker has the advantage of being easy to measure, it is noted that its relationship with sex hormone levels at specific stages of life has not yet been well quantified, and it has still been questioned. Hence, it is suggested that those findings from studies involving 2D:4D as a proxy for foetal hormone exposure should be interpreted with caution, as well as those studies which claim its association with cancer. Thus, this review shows the need for a greater number of epidemiological studies using more homogeneous methodology and techniques to better investigate the strength of the findings.

Asociación entre el cociente del segundo y cuarto dedo y el riesgo de cáncer de próstata: Un estudio de casos y controles en población mediterránea

Objetivo Evaluar la asociación entre el cociente de los dedos segundo y cuarto (2D:4D), como un biomarcador de la exposición prenatal a andrógenos, y la presencia de cáncer de próstata (CaP).

Métodos Estudio de casos y controles con 260 hombres que consultaron en el Servicio de Urología del Hospital General Universitario Reina Sofía (Murcia, España). Los casos (n = 125) fueron pacientes diagnosticados de CaP por anatomía patológica a los que se les realizó una prostatectomía radical. Los controles (n = 135) fueron pacientes que consultaron en Urología por otro motivo y que no mostraron signos ni síntomas de patología prostática. La longitud del 2D y 4D de la mano derecha fue medida mediante un pie de rey digital y se calculó el cociente entre ambos (2D:4D). Para los análisis estadísticos se utilizaron modelos de regresión logística obteniendo Odds ratios (OR) crudas y ajustadas e intervalos de confianza al 95%.

Resultados Los casos presentaron un cociente 2D:4D significativamente menor que los controles. El cociente 2D:4D se relacionó significativamente con la presencia de CaP. Tras el ajuste multivariante, se observó que los varones que se encontraban en el primer tercil de distribución del cociente 2D:4D, presentaban casi el doble de riesgo de padecer CaP (OR 1,9: IC 95% 1,1–4,0; P-valor = 0,040) en comparación con los varones que se encontraban en el segundo y tercer tercil.

Conclusiones Una mayor exposición prenatal a andrógenos, reflejada por un cociente 2D:4D menor, podría estar asociado con riesgo aumentado de padecer CaP, pero más estudios son necesarios para corroborar esos hallazgos.

Can second to fourth finger ratio play a role in determining the risk of benign prostatic enlargement

Benign prostatic enlargement (BPE) is a disease that testosterone plays a role in its aetiology. Second to fourth finger ratio is a marker of prenatal androgenic exposure and may be a risk factor for several androgen-related diseases such as BPE. In this study, we investigated the relationship between the second to fourth finger ratio and BPE. A total of 63 patients with BPE were included for study group, and age-matched 63 healthy patients were included as a control group. Finger was measured by the distance from the proximal crease to the tip by using a digital caliper. The mean age of patients with BPE and non-BPE was 62 ± 8.9 and 61.5 ± 7.1 years respectively. There was statistically significant difference between groups in terms of prostate-specific antigen levels, prostate volumes and international prostate symptom scores. The mean finger ratios for right and left hand were 0.97 ± 0.03, 0.99 ± 0.03(p = .001) and 0.93 ± 0.15, 0.98 ± 0.03(p < .001) for BPE and non-BPE groups respectively. Men with a lower second to fourth finger ratio have higher risk of developing BPE than men without BPE. Therefore, the second to fourth finger ratio, which is indicative of prenatal androgen exposure, can be used as a marker of BPE risk.

2D:4D and spatial abilities: From rats to humans

Variance in spatial abilities are thought to be determined by in utero levels of testosterone and oestrogen, measurable in adults by the length ratio of the 2nd and 4th digit (2D:4D). We confirmed the relationship between 2D:4D and spatial performance using rats in two different tasks (paired-associate task and watermaze) and replicated this in humans. We further clarified anatomical and functional brain correlates of the association between 2D:4D and spatial performance in humans.

The Association of Digit Ratio (2D : 4D) with Cancer: A Systematic Review and Meta-Analysis

Objective

Intrauterine sex hormone environment as indicated by the second to the fourth digit ratio (2D : 4D) can be associated with cancer risk. This systematic review and meta-analysis aimed to evaluate the association of 2D : 4D with cancer diagnosis, malignancy, and age at presentation.

Methods

Studies that evaluated the association of 2D : 4D with cancer risk were collected from Pubmed/MEDLINE and Clarivate Analytics databases. Nineteen studies were included in the qualitative analysis.

Results

The 2D : 4D ratio was studied in prostate cancer, breast cancer, testicular cancer, gastric cancer, oral cancer, brain tumors, and cervical intraepithelial neoplasia. Low 2D : 4D was associated with prostate cancer, gastric cancer, and brain tumors, while high 2D : 4D, with breast cancer risk and cervical dysplasia. The 2D : 4D ratio was not associated with prostate, breast, and gastric cancer stage. Greater 2D : 4D ratio was associated with younger presentation of breast cancer and brain tumors. The meta-analyses demonstrated that testicular cancer was not associated with right-hand 2D : 4D ratio (p = 0.74) and gastric cancer was not associated with right-hand (p = 0.15) and left-hand (p = 0.95) 2D : 4D ratio.

Conclusions

Sex hormone environment during early development is associated with cancer risk later in life. Further studies exploring the link between intrauterine hormone environment and cancer risk are encouraged.

Prognostic significance of the digit ratio after hormone therapy for prostate cancer: a prospective multicenter study

The digit ratio has been used as a retrospective noninvasive biomarker to investigate the putative effects of prenatal exposure to androgens. In recent years, many scholars have paid attention to the association between 2D:4D (the second and fourth digits) and prostatic cancer. This study explored the prognostic significance of digit ratio in prostate cancer patients. We reviewed the progressive status and survival of 382 prostate cancer patients who had received hormone therapy at our institutions. Survival of clinicopathological variables analyzed as categorical variables were determined by the log-rank test. According to Cox’s proportional hazards analysis, R2D:4D, L2D:4D, PSA at 6 month,bone metastasis were significant independent factors for prostate cancer. The risk of any progression of prostate cancer similarly depressed with increasing 2D:4D, for any progression (R2D:4D HR = 0.71, p = 0.003; L2D:4D HR = 0.67, p = 0.001), for cancer-specific death (R2D:4D HR = 0.67, p = 0.025; L2D:4D HR = 0.74, p = 0.036). Digit ratio may not only have predictive value in risk but also prognosis of prostatic cancer. This finding suggests that low 2D:4D can be used as prognostic factors to identify patients with a poor prognosis. These patients may benefit from more aggressive management.

Comparison of digit ratio (2D:4D) between Brazilian men with and without prostate cancer

BACKGROUND

Digit ratio (2D:4D) has been suggested as a proxy biomarker for prenatal androgen activity and has been linked to prostate cancer, as the genes that regulate the formation and differentiation of the fingers are also related to the carcinogenesis of prostate cancer. To investigate the possible correlation between right hand, left hand and right hand minus left hand (DR-L) 2D:4D and prostate cancer of Brazilian subjects by comparing 2D:4D ratios of individuals diagnosed with prostate cancer and individuals without the disease. Also, to inquire the relationship between 2D:4D and severity of prostate cancer through Gleason scores.

METHODS

Digital measurements of the lengths of the index and ring fingers of both hands of patients diagnosed with prostate cancer (PCA group, n=100) and healthy control individuals (n=100) were obtained using a digital vernier caliper. Means of the 2D:4D ratios were compared. Data were analyzed by the Student's t-test for unpaired samples, Mann-Whitney test and Spearman's correlation with a significance level of 5%.

RESULTS

The PCA group presented significantly lower right and left 2D:4D (P=0.001 and P=0.002, respectively) in comparison to healthy controls, but DR-L were not significantly different between groups (P=0.589). In addition, digit ratios were not correlated to Gleason score for either hand or in DR-L.

CONCLUSIONS

2D:4D seems to be a marker for screening patients for prostate cancer in an admixed population, as males with prostate cancer present lower 2D:4D than healthy subjects. On the other hand, 2D:4D does not appear to be associated with the severity of prostate cancer.

Sex-different abnormalities in the right second to fourth digit ratio in Japanese individuals with autism spectrum disorders

Background

The prevalence of autism spectrum disorders (ASDs) is higher in men than in women. The extreme male brain theory proposes that excessive prenatal testosterone activity could be a risk factor for ASDs. However, it is unclear whether prenatal sex hormone activity is a risk factor for women. The ratio of the length of the second to fourth digits (2D:4D) is considered to be a biomarker of the prenatal ratio of testosterone to estrogen. Therefore, this study compared the 2D:4D ratios of women with and without ASDs to determine if prenatal sex hormone activity could be a risk factor for ASDs in women.

Methods

The study included 35 Japanese men with ASDs, 17 Japanese women with ASDs, 59 typically developed (TD) Japanese men, and 57 TD Japanese women. We measured digit lengths and compared the 2D:4D ratios among the four groups. We also examined the relationship between the 2D:4D ratio and the autism-spectrum quotient score of each group.

Results

In our cohort, men with ASDs tended to have lower right-hand 2D:4D ratios relative to TD men. In contrast, the right 2D:4D ratios in women with ASDs were higher compared to those of TD women. No significant correlations were found between the 2D:4D ratios and the autism-spectrum quotient scores in any group. The higher right 2D:4D ratios in women could not be explained by age or full-scale intelligent quotients. This group difference was not found for the left 2D:4D or right–left 2D:4D ratios.

Conclusions

We found a reverse direction of abnormality in the right 2D:4D ratio for men and women with ASDs. It has been posited that high prenatal testosterone levels lead to a lower 2D:4D ratio. However, a recent animal study showed that testosterone injection to dam leads to a higher right 2D:4D ratio especially for female offspring, which might be mediated by abnormal adipose accumulation in the fingertip. Therefore, the present findings suggest that high prenatal testosterone could be a risk factor both for Japanese men and women with ASDs, elucidating one potential etiology of ASDs in women.

From palmistry to anthropometry: can 2nd to 4th digit length (2D:4D) predict the risk of prostate cancer?

OBJECTIVE

The 2nd to 4th digit length (2D:4D) is inversely related to androgen exposure during the fetal period, which may represent a risk factor for several steroid-related diseases. We aimed to evaluate the relationship between 2D:4D ratio and the risk of developing prostate cancer (PCa).

SUBJECTS AND METHODS

We assessed the 2D:4D ratio of 474 men >40 years old, stratified into three groups: group 1 (n = 222) patients with PCa, group 2 (n = 82) subjects with high risk of PCa, and group 3 (n = 170) men with low risk of PCa. Subjects were submitted to a digital picture of the ventral surface of the right hand and 2nd and 4th fingers measurements were determined by the distance from the proximal crease to the tip using computer-assisted analysis.

RESULTS

The mean serum prostate-specific antigen level was 7.5 ng/ml in the high-risk group and 0.92 ng/ml in the low-risk group (p < 0.05). The mean 2D:4D ratios were 0.96 ± 0.04, 0.97 ± 0.04 and 0.96 ± 0.04 for the PCa, high-risk and low-risk groups, respectively, and no difference was found among the three groups (p = 0.12).

CONCLUSION

Anthropometry of the hand using the 2D:4D ratio is not a predictor of PCa.

Second to fourth digit ratio confirms aggressive tendencies in patients with boxers fractures

BACKGROUND

Upper limb second to fourth digit ratio (2D:4D) has been shown to be dependent on prenatal androgen exposure. A longer relative fourth digit to second digit is indicative of increased intrauterine testosterone exposure prenatally and the converse is also true for oestrogen exposure. The 2D:4D ratio has implications in the sporting, academic, financial and sexual arenas. The purpose of this study was to examine the association between smaller finger length ratios (2D:4D) and boxers fractures, in both men and women, by comparing the 2D:4D ratios in 150 boxers fractures and comparing them to matched controls. Boxers fractures are an injury classically incurred during acts of aggression and we postulated that this cohort of patients would have a smaller 2D:4D ratio in comparison to the normal population mean ratio.

METHODS

One hundred and fifty radiographs from patients with boxers fractures secondary to aggressive actions were analysed and the 2D:4D ratio was calculated. A further 150 X-rays from patients not involved in aggressive activities were used as a control group and the 2D:4D ratio was calculated in the same manner. We then performed statistical analysis to compare the 2D:4D ratios between our two groups.

RESULTS

As predicted, the 2D:4D in males was smaller than females in all of the groups. However, our results showed that those presenting with a boxers fracture due to an aggression related injury had a statistically significant smaller 2D:4D ratio when compared to the normal population.

CONCLUSION

Boxers fractures are injuries that typically occur from an aggressive act. It is well documented that a low 2D:4D ratio is reflective of an increased prenatal exposure to androgens, particularly testosterone. We have shown that boxers fractures are associated with a smaller 2D:4D ratio than the normal population, thus suggesting that persons exposed to high levels of prenatal androgens are more likely to exhibit aggressive tendencies in adulthood. Our results suggest that smaller digit ratios may predict a predisposition to acts of aggression, and as such result in an increased likelihood of sustaining an injury such as a boxers fracture. This relationship seems to be present independently of gender.