Luteinizing hormone in testicular descent.

A proper hypothalamus-pituitary-testis axis with normal androgen synthesis and action is a prerequisite for normal testicular descent. Various defects in this axis may result in cryptorchidism but endocrine abnormalities are rarely detected. Androgens regulate testicular descent but androgen action alone is not sufficient for normal testicular descent. The regulation of androgen production is influenced both by placental human chorionic gonadotropin (hCG) and pituitary luteinizing hormone (LH). There is evidence that the longer pregnancy continues, the more important role pituitary LH may have. Insulin-like hormone-3 (INSL3) is suggested to be the main regulator of gubernacular development and therefore an apparent regulator of testicular descent. INSL3 production is also related to LH, and reduced INSL3 action is a possible cause for cryptorchidism. Cryptorchid boys have normal testosterone levels with slightly but significantly elevated LH levels as compared to healthy boys. This high gonadotropin drive may compensate for mild Leydig cell dysfunction in cryptorchidism.

Mild gestational diabetes as a risk factor for congenital cryptorchidism.

CONTEXT: Cryptorchidism is the most common malformation in newborn boys. Maternal diabetes has previously been suggested to be a risk factor for this disorder in one epidemiological study. OBJECTIVE: Evaluation of the prevalence of maternal glucose metabolism disorders during pregnancy in newborn boys having normal testicular descent or congenital cryptorchidism. DESIGN: Postnatal analysis of maternal history concerning glucose metabolism abnormalities during pregnancy among cryptorchid and healthy Finnish boys. SETTING AND PARTICIPANTS: The material of this case-control study comprises 1163 boys with normal testicular descent at birth and 125 boys with congenital cryptorchidism. All these singleton Finnish boys were born in Turku University Central Hospital (1997-2001) and were examined at birth and/or at the expected date of delivery. MAIN OUTCOME MEASURES: Information about maternal diabetes diagnosis and abnormality of the result of a 2-h 75-g oral glucose tolerance test during pregnancy were obtained from the hospital records after delivery. RESULTS: After adjustment for possible confounding factors, i.e. maternal smoking during pregnancy, maternal age at delivery, and risk factors of cryptorchidism, e.g. prematurity and weight for gestational age, abnormal maternal glucose metabolism was significantly more common in the group of cryptorchid boys [diet-treated gestational diabetes, P = 0.0001; odds ratio, 3.98 (95% confidence interval, 1.97-8.05); diet-treated gestational diabetes or only an abnormal result in oral glucose tolerance test, P = 0.0016; odds ratio, 2.44 (95% confidence interval, 1.40-4.25)] when compared with boys with normal testicular descent. CONCLUSIONS: Mildly abnormal glucose metabolism during pregnancy was associated with an increased risk for congenital cryptorchidism. The mechanism remains to be elucidated.

Larger testes and higher inhibin B levels in Finnish than in Danish newborn boys.

CONTEXT: Recent studies showed that male reproductive health problems, such as cryptorchidism, hypospadias, testicular cancer, and low sperm quality, are more prevalent in Denmark than in Finland. OBJECTIVES: We hypothesized that, if fetal testicular dysgenesis contributed to these observations, differences in gonadal development and the hypothalamus-pituitary-testis axis would already be detectable perinatally. Thus, we investigated healthy newborn boys in both countries. DESIGN: This was a prospective, longitudinal population-based study. SETTING: Two primary obstetric centers were included at the University Hospitals of Copenhagen, Denmark, and Turku, Finland. PARTICIPANTS: The participants of the study included 633 Danish and 1044 Finnish boys, born at term with appropriate weight for gestational age. INTERVENTIONS: Ultrasound determination of testis size at 0, 3, and 18 months and blood sampling (n = 727) at 3 months were analyzed. MAIN OUTCOME MEASURES: Testicular volume and reproductive hormones were measured. RESULTS: Testis volume was significantly higher at all ages in Finnish than in Danish boys (medians, 98 vs. 95, 185 vs. 119, and 188 vs. 136 mm(3), respectively; P < 0.00001). Testis growth from birth to 3 months was larger in Finnish than in Danish boys (mean, 75 vs. 26 mm(3); P < 0.0001). Serum hormone levels were higher in Finnish than Danish boys for inhibin B (median, 456 vs. 385 pg/ml; P < 0.0001), FSH (1.33 vs. 1.21 IU/liter; P < 0.036), and SHBG (143 vs. 136 nmol/liter; P < 0.022). Inhibin B was significantly positively correlated to testicular volume (r = 0.25; P < 0.006). CONCLUSIONS: The larger testes and higher inhibin B levels most likely represent a bigger volume of seminiferous tubules in Finnish compared with Danish boys. Although this phenomenon may be attributable to a genetic difference between the two countries, it may also reflect environmental factors influencing testicular development.

Human breast milk contamination with phthalates and alterations of endogenous reproductive hormones in infants three months of age.

UNLABELLED: Phthalates adversely affect the male reproductive system in animals. We investigated whether phthalate monoester contamination of human breast milk had any influence on the postnatal surge of reproductive hormones in newborn boys as a sign of testicular dysgenesis. DESIGN: We obtained biologic samples from a prospective Danish-Finnish cohort study on cryptorchidism from 1997 to 2001. We analyzed individual breast milk samples collected as additive aliquots 1-3 months postnatally (n = 130; 62 cryptorchid/68 healthy boys) for phthalate monoesters [mono-methyl phthalate (mMP), mono-ethyl phthalate (mEP), mono-n-butyl phthalate (mBP), mono-benzyl phthalate (mBzP), mono-2-ethylhexyl phthalate (mEHP), mono-isononyl phthalate (miNP)]. We analyzed serum samples (obtained in 74% of all boys) for gonadotropins, sex-hormone binding globulin (SHBG), testosterone, and inhibin B. RESULTS: All phthalate monoesters were found in breast milk with large variations [medians (minimum-maximum)]: mMP 0.10 (< 0.01-5.53 microg/L), mEP 0.95 (0.07-41.4 microg/L), mBP 9.6 (0.6-10,900 microg/L), mBzP 1.2 (0.2-26 microg/L), mEHP 11 (1.5-1,410 microg/L), miNP 95 (27-469 microg/L). Finnish breast milk had higher concentrations of mBP, mBzP, mEHP, and Danish breast milk had higher values for miNP (p = 0.0001-0.056). No association was found between phthalate monoester levels and cryptorchidism. However, mEP and mBP showed positive correlations with SHBG (r = 0.323, p = 0.002 and r = 0.272, p = 0.01, respectively); mMP, mEP, and mBP with LH:free testosterone ratio (r = 0.21-0.323, p = 0.002-0.044) and miNP with luteinizing hormone (r = 0.243, p = 0.019). mBP was negatively correlated with free testosterone (r = -0.22, p = 0.033). Other phthalate monoesters showed similar but nonsignificant tendencies. CONCLUSIONS: Our data on reproductive hormone profiles and phthalate exposures in newborn boys are in accordance with rodent data and suggest that human Leydig cell development and function may also be vulnerable to perinatal exposure to some phthalates. Our findings are also in line with other recent human data showing incomplete virilization in infant boys exposed to phthalates prenatally.

Hormonal changes in 3-month-old cryptorchid boys.

CONTEXT: Hormonal dysregulation has been suggested to be one of many etiological factors of cryptorchidism. OBJECTIVES: The objective of this study was to assess the hypothalamic-pituitary-testicular axis in cryptorchid boys during the postnatal hormonal surge. DESIGN: This was a prospective, longitudinal, population-based study. SETTING: The study was performed at two primary obstetric centers. PARTICIPANTS: Study participants included 388 Finnish and 433 Danish boys (88 and 34 with cryptorchidism, respectively). INTERVENTIONS: Clinical examinations were performed at 0 and 3 months. Blood samples were taken at 3 months. MAIN OUTCOME MEASURES: The main outcome measures were testis position and reproductive hormone levels. RESULTS: Finnish cryptorchid boys had significantly higher FSH [1.59 (0.50-3.53) vs. 1.30 (0.49-2.92) IU/liter; P < 0.0001] and lower inhibin B [426 (254-770) vs. 459 (266-742) pg/ml; P < 0.015] levels than Finnish control boys [median (2.5th-97.5th percentiles)]. Danish cryptorchid boys had higher FSH levels than controls [1.47 (0.54-3.89) vs. 1.18 (0.41-3.04) IU/liter; P = 0.018]. Inhibin B levels in healthy Danish boys were lower than those in Finnish boys [380 (233-637) pg/ml; P < 0.0001] and were not reduced in Danish crypt-orchid boys [392 (236-672) pg/ml; P = 0.851]. Changes in hormone levels were strongest in boys with severe, persistent cryptorchidism, but were also detectable in mild and transient cryptorchidism. Effects on Leydig cell function were subtle, with an increase in LH in Finnish (but not Danish) cryptorchid boys vs. controls [1.97 (0.77-5.91) vs. 1.75 (0.58-4.04) IU/liter; P < 0.021], but testosterone levels remained within the normal range. CONCLUSIONS: Our results support the hypothesis that cryptorchidism is associated with a primary testicular disorder, which could be a cause or a consequence of cryptorchidism. This malfunction is reflected by low inhibin B production in the Finnish cohort and high gonadotropin drive in both the Finnish and Danish cohorts.

Postnatal penile length and growth rate correlate to serum testosterone levels: a longitudinal study of 1962 normal boys.

OBJECTIVE: Infant boys show a brief activation of their hypothalamic-pituitary-gonadal axis shortly after birth, the physiological significance of which is poorly understood. The objective of the study was to investigate the correlation between endogenous testosterone levels and penile size and growth. DESIGN: Prospective, longitudinal population-based study taking place at two large primary obstetric centres at the University Hospitals of Copenhagen, Denmark, and Turku, Finland. METHODS: Infant boys, 728 Danish and 1234 Finnish, underwent clinical examinations at 0, 3, 18 and 36 months in Denmark and at 0, 3 and 18 months in Finland with blood samples taken at 3 months (n = 630). Penile length and growth were registered and reproductive hormones (testosterone, sex hormone binding globulin, oestradiol) were analysed. RESULTS: Penile length increased from birth (3.49+/-0.4 cm) to 3 years of age (4.53+/-0.51 cm) with the highest growth velocity from birth to 3 months (1.0 mm/month). Penile length and growth were significantly, positively correlated to serum testosterone (r = 0.31 and 0.076, P = 0.006 and 0.001 respectively) and to free testosterone index (r = 0.385 and 0.094, P = 0.0001 and 0.0001 respectively). CONCLUSIONS: We found that endogenous testosterone was significantly associated with penile size and growth rate in infant boys. Thus, the postnatal surge in reproductive hormones appears to be important for genital growth. Our data may serve as an updated reference for normal penile length in Caucasian boys up to 3 years of age.

Does variant luteinizing hormone (V-LH) predispose to improper testicular position in late pregnancy?

Undescended testes are a common urogenital malformation affecting 2-9% of newborn boys. The etiology of cryptorchidism is probably heterogeneous, but insufficient androgen effect has been recognized as one cause of the condition. A common genetic variant (V) form of LH occurs in apparently healthy individuals universally. Compared with wild-type (WT) LH, the V-LH molecule has increased bioactivity in vitro but shorter half-life in vivo. In the present study, we screened 93 cryptorchid (59 uni- and 34 bilateral) and 211 healthy boys for the occurrence of V-LH to evaluate whether it is related to testicular descent. Two immunofluorometric assays with different combinations of MAb, one detecting WT-LH, the other detecting both WT- and V-LH, were used to measure LH concentrations. The ratio of two LH measurements was used to assess the V-LH status. The prevalence of V-LH was similar in the control and cryptorchid groups, and the total prevalence of V-LH corresponded well to the prevalence of V-LH in general Finnish population. Among cryptorchid boys, the prevalence of V-LH was dependent on gestational age: 6.7% at GA <37, 20.9% at GA 37-39, and 42.9% at GA of 40-42 wk. In contrast, the percentage of V-LH status was similar at different gestational ages in all control groups. We conclude that V-LH is not critical for normal testicular descent but the increased prevalence of V-LH among cryptorchid boys with GA >40, suggests that the lower hormonal efficacy of V-LH predisposes for improper testicular descent in late pregnancy.

Cryptorchidism: an indicator of testicular dysgenesis?

Cryptorchidism is a common ailment of new-born boys, affecting 1-9% of full term boys at birth. Cryptorchidism has been associated with an increased risk of testicular cancer and reduced fertility. Aetiology of cryptorchidism remains obscure in most cases. Familial occurrence suggests a heritable susceptibility to cryptorchidism; however, seasonal variation in the incidence of cryptorchidism suggests that environmental factors also contribute. Testicular descent is characterised by androgen-dependent regression of cranial suspensory ligament and androgen + insulin-like hormone 3 (Ins l3)-dependent gubernacular outgrowth. Even though hormonal defects are rarely detected in patients, both hypo-and hypergonadotropic hormonal patterns have been associated with cryptorchidism. Moreover, cryptorchid boys have significantly reduced serum androgen bioactivity at 3 months of age when normal boys have a strong surge of reproductive hormones. Defects in Ins l3 action cause cryptorchidism in male mice, and over-expression in female mice causes ovarian descent. Defects in leucine-rich repeat-containing G-protein-coupled receptor 8/G-protein-coupled receptor affecting testis descent (LGR8/GREAT), the receptor for Ins l3, manifest the same phenotype as Ins l3 knockout mutants. Even though mutations found in Ins l3 and LGR8/GREAT genes are not a common cause of cryptorchidism in patients, it remains to be resolved whether low Ins l3 levels during development are associated with cryptorchidism. Cryptorchidism may reflect foetal testicular dysgenesis that may later manifest as subfertility or testicular cancer.

Circannual rhythm in the incidence of cryptorchidism in Finland.

Conflicting data on circannual variation in birth rates of urogenital malformations have been reported previously. To assess risk factors of cryptorchidism we studied the seasonal variation of cryptorchidism in Finland. We performed a prospective cryptorchidism study in Turku, Finland, from 1997 to 2001 to evaluate the incidence of cryptorchidism. Clinical examinations were performed at birth and at 3 months. Of 9511 liveborn boys (1471 preterm boys) 216 (53 preterm boys) were cryptorchid at birth and 106 (19 preterm boys) at 3 months. The incidence of cryptorchidism was significantly higher in spring (February-April) (3.0%) than in summer (May-July) (1.7%) (OR 1.79; 95% CI: 1.23-2.63). This seasonal difference was observed both among preterm and term boys. We conclude that a circannual fluctuation in the incidence of cryptorchidism exists, which indicates an influence by environmental factors. The underlying reason for cyclicity affects similarly both preterm and term boys.

Lack of LGR8 gene mutation in Finnish patients with a family history of cryptorchidism.

Cryptorchidism is the most frequent congenital anomaly of the urogenital tract in the male. Although in Western countries 1-2% of males at the age of 3 months are diagnosed with this condition, its aetiology is still unknown. Animal models suggest a possible genetic basis for this disorder. Recently, the INSL3 (Leydig insulin-like peptide) gene and its cognate receptor, LGR8, were found to be important in testicular descent by regulating gubernacular development. Male mice null for either INSL3 or LGR8 genes exhibited bilateral cryptorchidism. Because earlier studies indicated that mutation of the INSL3 gene is not associated with the development of human cryptorchidism, this study analysed whether mutations in the LGR8 gene could be associated with this disorder. Sequencing of 18 exons of the LGR8 gene in 23 cryptorchid Finnish patients and a group of 33 control subjects allowed the identification of three nucleotide changes in exons 12 and 17, showing single base substitutions from A to G at positions 957, 993, and 1810 of LGR8. Among the three changes, only the 1810 A to G substitution is associated with an amino acid change from isoleucine to valine (Ile604Val) located in the fifth transmembrane domain of this seven-transmembrane receptor. This change was more frequent in a control group of normal fertile adult males and infant boys than in the group of cryptorchid males. The change is not associated with altered receptor signalling, thus suggesting the presence of a polymorphism unrelated to the cryptorchid phenotype. These data indicate that mutations involving the human LGR8 gene do not represent a frequent cause of cryptorchidism in the Finnish population.

Serum androgen bioactivity in cryptorchid and noncryptorchid boys during the postnatal reproductive hormone surge.

The first postnatal months of life in boys are characterized by activation of the hypothalamic-pituitary-testicular axis that results in the well depicted surge of reproductive hormones. Serum testosterone levels at that time are high, but infants do not display signs of virilization, and subsequently there is only indirect evidence that circulating androgens during the surge are biologically active. We used a recombinant cell bioassay to determine serum androgen bioactivity in 80 3-month-old boys born after full-term pregnancies (37-42 wk) in whom localization of the testes was determined by palpation after birth and at a mean age of 3 months. At that age, serum androgen bioactivity ranged from less than 0.8 to 1.9 nM testosterone equivalents and correlated with serum testosterone concentration (r = 0.71; P < 0.0001; n = 34), free androgen index (r = 0.80; P < 0.0001; n = 34), age (r = -0.29; P < 0.01; n = 80), and localization of the testes (r = -0.24; P < 0.05; n = 80). Moreover, all boys in this study with detectable androgen bioactivity (n = 26) had testes located in scrotal or high scrotal position (n = 64), whereas all boys (n = 16) with at least 1 suprascrotal, inguinal, or nonpalpable testis had nonmeasurable androgen bioactivity in serum (P < 0.01). We conclude that 3-month-old boys are exposed to biological effects of androgens during the postnatal activation of the hypothalamic-pituitary-testicular axis, and that this exposure may be reduced in boys with at least 1 testis located superior to the scrotum.

Genetics and hormones in testicular descent.

Testicular descent is an essential part of normal male sexual development. Any anomaly that disrupts normal testicular descent will be clinically evident as cryptorchidism. Several factors, such as Hoxa-10, epidermal growth factor (EGF), calcitonin gene-related peptide (CGRP), and hormones, especially androgens and insulin-like factor 3 (INSL-3), have been suggested as being regulators of testicular descent. Testicular descent from the lower pole of the kidney into the extra-abdominal scrotal sac is a two-stage process of transabdominal and inguino-scrotal migration. The transabdominal phase is androgen independent, whereas the inguino-scrotal phase depends on androgen action. Disruption of androgen action eg. by environmental anti-androgens are suspected as contributing to cryptorchidism. Estrogens can down-regulate INSL-3 production and thereby disturb testicular descent. Familial occurrence in some cases suggests a possible genetic background for cryptorchidism.

Natal and neonatal teeth in relation to environmental toxicants.

Infants born to mothers heavily exposed to polychlorinated biphenyls (PCBs) and dibenzofurans (PCDFs) have earlier been reported to have increased prevalences of natal and neonatal teeth. Some tendency toward higher prevalence figures of natal and neonatal teeth can be seen in the literature in normal child populations during the last 40 y. We therefore decided to determine the present prevalence of these teeth in a Finnish population and to evaluate whether infants with natal and neonatal teeth are more exposed to PCBs, PCDFs, and polychlorinated dibenzo-p-dioxins (PCDDs) than infants on average. A total of 34,457 infants born in 1997-2000 in four hospitals in southern Finland were examined for natal and neonatal teeth. The exposure of the infant to PCBs and PCDD/Fs was evaluated by measuring the levels of 17 most toxic PCDD/F and 36 PCB congeners in his or her mother's milk sample when the child was 4-8 wk old. A total of 34 infants had one or two natal (29 infants) or neonatal teeth (five infants). The milk analyses showed that the median level of PCDD/Fs as toxic equivalent (World Health Organization-recommended 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalent quantity for PCDD/Fs in fat) was 11.9 pg/g in fat, and that of PCBs (World Health Organization-recommended 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalent quantity for PCBs) was 7.24 pg/g in fat. These levels corresponded to the prevailing levels. The results showed that the prevalence of natal and neonatal teeth was 1:1000. No association was found between pollutant levels and occurrence of natal and neonatal teeth, indicating that the prevailing levels of PCDD/Fs and PCBs are likely to be below the threshold to cause perinatal eruption of teeth.