In mixed gender reports, CT has been associated with AL [4, 5]. In the present study, CT was not significantly associated with AL in women. The number of participants was small and the variability may have been large. However, some have reported the gender difference [18, 19]. Similarly, there may be differences in hormone levels between men and women. It is possible that taller participants may secrete more GH and have longer AL. We first focused on the possible influence of GH on AL.
It has been reported that the peak mean refractive values of patients with GH deficiency tend to be hyperopic, while the peak mean refractive values of control healthy children tend to be myopic .
de Graaf et al. reported that in children with severe growth retardation due to chronic renal failure, GH therapy maintained equal growth in height and all body segments, with no signs of disproportionate growth in mixed-gender data . On the other hand, Bannink et al. reported that girls with Turner syndrome were treated with GH therapy and grew proportionally except for FL .
In our study, there was a significant positive correlation between FL/BH and AL only in men. It has been speculated that GH does not necessarily cause each part to grow in equal proportions and that there may be sex differences . Recently, AL in a group of acromegaly patients did not show any significant difference from the control group . Therefore, it is necessary to consider not only GH, but also other factors.
In the chick model of myopia, it has been estimated that chondrocyte proliferation and expression of growth factors such as TGF-β are higher in the posterior sclera than in control eyes . In a chick model, a correlation between AL and TGF-β has been found . In humans, the amount of TGF-β2 in the aqueous humor is significantly correlated with AL . It has also been reported that TGF-β is increased by GH .
Thus, TGFβ is expected to be a growth factor for AL. Female growth factors belonging to the TGFβ superfamily are also expressed developmentally in ovarian somatic cells and oocytes, and have been found to function as intrafollicular regulators of folliculogenesis .
Therefore, we hypothesized that when ovarian function is overactive, TGF-β may increase and AL may elongate regardless of the degree of GH secretion. From this study, we may be able to obtain an association between FL/BH and AL in men, but it may be difficult in women because of other factors such as increased ovarian function. Even if BH is short, the cause of AL elongation may be due to TGF-β and other factors.
One of the strengths of our study is that we found that the association between FL/BH and AL is appropriate for men. This is the first report of its kind, to our knowledge.
In conclusion, there was a significant association between FL/BH and AL in men, suggesting that factors determining each body size may be different in men and women, although the possibility remains that factors determining BH, FL, and HL are related to AL.