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[Discussion]
Testicular descent is regarded as a result of complex
interactions between mechanical and hormone factors. The process
may be divided into a first transabdominal phase and a second
inguinoscrotal phase. The first phase is believed to be
controlled by non-androgenic hormones and mullerian inhibiting
substance (MIF) from the fetal testicles rather than by
androgens, while the second phase is presumably dependent on
androgens from the Ledig cells of fetal testicles.
Epidemiologic studies have reported mothers' exposure to
estrogen preparations or DES during gestation as risk factors
(Gill 1979, Whitehead 1981, Cosgrove 1977, Depue 1984). Estrogen
exposure is considered to result in inhibition of MIS that
controls the first phase of testicular descent, and inhibition
of testosterone secretion via suppressing the activity of the
fetal Leidig cell precursors, thus affecting the second phase.
Some of endocrine-disrupting organochlorine compounds act as
estrogen receptor agonists and affect hormone levels.
Epidemiologic studies had found before Dec. 31, 2000, odds rate
increase for mothers handling pesticides (Kristensen 1997,
Weidner 1998) and higher fat levels of organochlorines
(heptachlor epoxide, hexachlorobenzene) in cryptorchidism
patients than in normal boys (Hosie 2000). Survey of more recent
papers found case-control studies reporting association with
pesticide exposure. However, quantitative analysis of exposure
of victims to endocrine disruptors using biological samples did
not find significant correlation. Studies are thus too few to
for definite conclusion on the association of endocrine
disruptors and cryptorchidism. Experimental designs with high
reliability are needed for future studies on this problem.
[Conclusions]
A survey of epidemiologic studies on cryptorchidism and
organochlorine compounds up to Oct. 31, 2004, found reports
indicating no association with the PCB level in patients' cord
blood, no association with mothers' serum DDE, and significant
link with HCE and HCB. Findings on effects of pesticides and
hormone preparations were inconclusive. Studies are thus too few
to for definite conclusion on the association of endocrine
disruptors and cryptorchidism. Experimental designs with high
reliability are needed for future studies on this problem.
[Literature]
Table 2.9.1:
Intervention studies on the relationship of endocrine disruptors
with cryptorchidism
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