Randomized, crossover comparison study of the short-term effect of oral testosterone undecanoate and intramuscular testosterone depot on linear growth and serum bone alkaline phosphatase

AIM

To compare the effects of oral testosterone undecanoate (TU) 40 mg daily and intramuscular depot sustanon 50 (SUS), 4 weekly, on short-term growth and bone turnover.

METHOD

Prospective, randomised, cross-over study over 26 weeks with 4 weeks of run-in, 8 weeks of treatment I (TU/SUS), 4 weeks of wash-out, 8 weeks of treatment II (SUS/TU) and 4 weeks of final wash-out.

MAIN OUTCOME MEASURES

Weekly change in lower leg length (LLL) as measured by knemometry, i.e. LLL velocity (LLLV) and absolute bone alkaline phosphatase levels (bALP), as well as percentage change in bALP (%bALP).

PATIENTS

Fourteen boys with delayed growth and puberty; two declined and one boy with sickle cell trait dropped out with priapism a week after SUS. The remainder had a median age of 14.3 years (range 12.5-17.4), testicular volume of 2 ml each (2-6), HtSDS of -2.1 (-3.3 to -1.0) and BA delay of 2.4 years (0.7-4.4).

RESULTS

Median LLLV in the treatment blocks was 0.7 mm/wk (-0.27 to 2.2) and LLLV during the run-in and wash-out periods was 0.27 mm/wk (-0.3 to 0.6) (p <0.005). LLLV during treatment with TU and SUS was 0.51 mm/wk (-0.22 to 2.17) and 0.67 mm/wk (-0.27 to 2.2), respectively (NS). Median LLLV during the washout phases that followed the TU block and the SUS block was similar at 0.28 mm/wk (-0.1 to 0.6) and 0.3 mm/wk (-0.2 to 0.6), respectively. LLLV peaks and troughs that were related to the timing of the injection were more evident during SUS therapy. Median bALP during the run-in period was 94.2 U/l (16-282) and the median %bALP during this period was 1.2% (-57, 16). The main rise in bALP occurred during the treatment blocks with a %bALP of 19.3% (-28.8, 121.7) (p <0.005). Median bALP at the beginning and end of the SUS block was 99.7 U/l (51.7, 225) and 170 U/l (64.8, 273), respectively (p <0.05). Median bALP at the beginning and end of the TU block was 111 U/l (51, 287) and 127.6 U/l (66.4, 298) (NS). Median %bALP during SUS was higher than during TU at 28.1% (4.4, 121.7) and 11.8% (-28.8, 83.6) (p = 0.07).

CONCLUSION

At the doses studied, testosterone undecanoate was as effective as sustanon at promoting short-term growth but changes in bone alkaline phosphatase were more marked during sustanon therapy.

Congenital adrenal hyperplasia: transitional care

Congenital adrenal hyperplasia (CAH) is a life-long disorder which poses management problems that are age- and sex-specific. The condition merits an organised, multi-disciplinary transitional care format similar to the kind that is now well established for Turner's syndrome in many centres. In the eyes of the paediatrician, achieving optimal growth is the primary target of CAH management during infancy and childhood. Fixation on this objective can be to the detriment of the patient because it may result in failure to appreciate the significance of metabolic disturbances that occur in later childhood, particularly in females, and which may be the progenitor of chronic problems with obesity, insulin resistance and infertility in adult life. Similarly, the care of the adult patient with CAH comprises more than just prescribing steroid replacement for primary adrenal insufficiency. The transition period between childhood and adulthood is an opportune time for review of the various management options and to assess the efficacy of steroid replacement, to consider alternative novel treatment modalities and to apply a checklist to the multi-faceted aspects of the medical, surgical and psychological needs of the patient.

Management of fetal endocrine disorders

A number of maternal endocrine disorders, when active during pregnancy, can have adverse effects on the newborn. Frequently, these affects can be anticipated as in Graves' disease, or the adverse effect can be prevented as in macrosomia in the infant of the diabetic mother. Occasionally, there are opportunities for prenatal treatment of a fetal endocrine disorder. For instance, a large goitre that may cause problems during delivery can be treated with thyroid hormones administered intra-amniotically or as analogues that cross the placenta. A uniquely effective form of treatment for prevention of a major birth defect is administration of dexamethasone to the mother to avoid virilisation of a female fetus with congenital adrenal hyperplasia (CAH). However, such treatment should only be conducted within the framework of a clinical trial as the long-term effects of exposure to potent glucocorticoids in utero are unknown. Intrauterine growth retardation, which affects about 5% of newborns, is currently not amenable to direct pharmacological treatment before birth. However, there are more practical options for managing this condition, including improved maternal nutrition and avoidance of toxins injurious to fetal growth.

Androgen receptor gene CAG repeat polymorphism in the development of ovarian hyperandrogenism

Ovarian hyperandrogenism, a key feature of polycystic ovary syndrome, is preceded by precocious pubarche (PP) (pubic hair < 8 yr) in some populations. We hypothesized that this earlier presentation may relate to increased androgen sensitivity, indicated by androgen receptor gene CAG repeat length. This polymorphism was genotyped in 181 Barcelona girls (age, 10.9 yr; range, 4-19 yr) who had presented with PP, and in 124 Barcelona control girls. PP girls had shorter mean CAG number than Barcelona controls (PP vs. controls: mean, range: 21.3, 7-31 repeats vs. 22.0, 15-32, P = 0.003) and greater proportion of short alleles 20 repeats or less (37.0% vs. 24.6%, P = 0.002). Among post-menarcheal PP girls (n = 69), shorter CAG number (biallelic mean </=20) was associated with higher 17-hydroxy-progesterone levels post leuprolide (P = 0.009), indicative of ovarian hyperandrogenism, higher testosterone levels (P = 0.02), acne (P = 0.03) and hirsutism scores (P = 0.01), and more menstrual cycle irregularities (P = 0.04). In multiple regression, ovarian hyperandrogenism risk was related to both low birth weight (SD <-1.5: odds ratio = 17.0; 95% confidence interval: 4.2-69.2) and shorter mean CAG number (20 or less repeats: odds ratio = 7.3; 1.3-42.0). In summary, shorter androgen receptor gene CAG number, indicative of increased androgen sensitivity, increases risks for PP and subsequent ovarian hyperandrogenism. Shorter CAG repeat alleles in Barcelona compared with United Kingdom women could lead to higher prevalences of these conditions.

Short-term effects of prednisolone and dexamethasone on circulating concentrations of leptin and sex hormone-binding globulin in children being treated for acute lymphoblastic leukaemia

OBJECTIVE

Disturbances in body weight regulation are often encountered during glucocorticoid treatment and are associated with increased insulin resistance and truncal fat accumulation. Children were investigated who were receiving glucocorticoid treatment for acute lymphoblastic leukaemia (ALL). They were randomized to receive either prednisolone or dexamethasone as part of induction of remission. This randomization process provided a suitable opportunity to compare the effects of these two administered steroid on surrogate markers of adipocyte activity (leptin) and hyperinsulinaemia/insulin resistance (SHBG).

DESIGN AND PATIENTS

Prospective study over 16 weeks of children randomized to receive prednisolone (40 mg/m2) or dexamethasone (6.5 mg/m2) as part of the MRC-ALL97/99 induction chemotherapy for ALL. Nineteen children (8 male, 11 female) with a median age 5.9 years (range 2.6-13 years) were recruited into the study. Main outcome measures were body mass index (BMI), serum leptin and sex hormone binding globulin (SHBG).

RESULTS

Glucocorticoid administration for 5 weeks resulted in significant (P < 0.05) increases in BMI, leptin (corrected for BMI) and the leptin : SHBG ratio and lowering of SHBG. Dose for dose, dexamethasone was significantly more potent than prednisolone in altering these parameters.

CONCLUSIONS

Short-term glucocorticoid treatment has significant effects on BMI, leptin and SHBG. The leptin : SHBG ratio increase indicates that this may be a novel and sensitive biochemical marker of metabolic change. Our results suggest that glucocorticoid treatment regimens should be kept as short as possible to avoid possible detrimental effects associated with increased adiposity and insulin resistance.

In-utero androgen exposure and 2nd to 4th digit length ratio-comparisons between healthy controls and females with classical congenital adrenal hyperplasia

BACKGROUND

Soft tissue measurements from the hand reveal lower second to fourth finger digit ratios (2D:4D) in males compared with females. The relatively longer 4th finger observed in males may be related to increased fetal exposure to androgens influencing the expression of Hox genes.

METHODS

We have measured 2D:4D ratios in 69 healthy females [median age 9.3 (range 1.9-17) years], 77 control males [median age 13.86 (2.1-20.3) years] and in 66 females with classical virilizing congenital adrenal hyperplasia (CAH) (median age 8.5 (1.1-16.2) years] who are known to be exposed to high concentrations of androgens in utero. Measurements were determined from X-rays of the left hand using vernier callipers. Intra-observer variability in measurement technique was 0.01%.

RESULTS

Control males had a significantly lower mean (SD) 2D:4D ratio [0.918 (0.029)] compared with female patients [0.927 (0.029), ANOVA P = 0.02]. No difference in 2D:4D ratio was observed between CAH females [0.925 (0.021)] and control females [0.927 (0.029)]. In contrast, 2D:4D ratio in males were significantly lower compared with CAH females (P = 0.03).

CONCLUSIONS

2D:4D ratios determined directly from radiographs of the left hand confirm significant differences between males and females. However, female patients with virilizing CAH do not have a male digit ratio pattern suggesting that in the left hand digit ratio development is not influenced by in-utero exposure to androgens.

Psychological outcomes and gender-related development in complete androgen insensitivity syndrome

We evaluated psychological outcomes and gender development in 22 women with complete androgen insensitivity syndrome (CAIS). Participants were recruited through a medical database (n = 10) or through a patient support group (n = 12). Controls included 14 males and 33 females, of whom 22 were matched to women with CAIS for age, race, and sex-of-rearing. Outcome measures included quality of life (self-esteem and psychological general well-being), gender-related psychological characteristics (gender identity, sexual orientation, and gender role behavior in childhood and adulthood), marital status, personality traits that show sex differences, and hand preferences. Women recruited through the database versus the support group did not differ systematically, and there were no statistically significant differences between the 22 women with CAIS and the matched controls for any psychological outcome. These findings argue against the need for two X chromosomes or ovaries to determine feminine-typical psychological development in humans and reinforce the important role of the androgen receptor in influencing masculine-typical psychological development. They also suggest that psychological outcomes in women with CAIS are similar to those in other women. However, additional attention to more detailed aspects of psychological well-being in CAIS is needed.

Reduced birth weight in boys with hypospadias: an index of androgen dysfunction?

Anthropometric birth measurements analysed for 51 boys with hypospadias identified in a prospective cohort study showed significant reductions in mean values for birth weight, length, and head circumference compared with controls. The absence of the usual sex dimorphism for these variables suggests that the results represent a marker of fetal androgen dysfunction in this subgroup of infants.

Short-term effects on linear growth and bone turnover in children randomized to receive prednisolone or dexamethasone

AIM

To compare the relative potency of prednisolone (Pred) and dexamethasone (Dex) on short-term growth and bone turnover.

METHOD

Prospective study over 16 weeks of children randomized to receive Pred (40 mg/m2) or Dex (6.5 mg/m2) for the first 5 weeks as part of the MRC-ALL97/99 induction chemotherapy for acute lymphoblastic leukaemia (ALL).

MEASUREMENTS

Lower leg length velocity (LLLV) and weight, serum IGF-I, serum bone alkaline phosphatase (bALP) levels and creatinine-adjusted, urinary excretion of deoxypyridinoline cross-links (DPD).

SUBJECTS

Nineteen children (eight boys, 11 girls) with a median age of 5.9 years (range 2.6-13) and with a diagnosis of ALL.

RESULTS

At week 2 of therapy, median LLLV in the Dex group was -1.5 mm/week (range 0.7 to -2.1) and significantly lower than the LLLV in the Pred group which was -0.1 mm/week (range 0.20 to -0.28; P < 0.05). In the Dex group, LLLV remained lower at week 8 (med LLLV, -0.3 mm/week, range 0 to -1.3) compared to LLLV in the Pred group at 0.3 mm/week (range 0.2-1.0; P < 0.05). Body weight showed an increase after week 2 and reached a peak in both groups of children at week 6. The change in weight from baseline was greater in the Dex group than the Pred group reaching a maximum change by week 5 of 17.5% (range 5-25) and 8.7% (range -3 to 18), respectively (P < 0.05). At presentation, median IGF-I level for the whole group was 83.5 micro g/l (range 31.8-293). IGF-I levels fell markedly during Dex therapy and continued to remain lower than baseline. At weeks 4, 6 and 8, median change in IGF-I from baseline was lower in the Dex group than the Pred group. From week 1 to week 3, median change in bALP was 72% (range -8 to 304) in the Pred group, whereas in the Dex group change in bALP was -1% (range 23 to -28; P < 0.005). By week 3, median bALP was higher in the Pred group at 65 U/l (range 36-187) than in the Dex group at 39 U/l (range 26-60; P < 0.05) but by week 6 median bALP in the Pred group had fallen to a similar level to the Dex group. At presentation, median DPD was 22 nmol/l (range 17-38) and 20 nmol/l (range 12-26) in the Pred and Dex groups, respectively (ns), reaching a nadir between weeks 3 and 6. The median percentage change in DPD in the Pred and Dex group from week 1 to week 3 was -34% (range -7 to 14) and -53% (range -6 to -69), respectively (ns). By week 8, DPD excretion had started to rise more dramatically in the Pred group such that the median DPD was 35 nmol/l (range 10-53) in the Pred group and 22 (range 9-30) in the Dex group (P < 0.05). On average, between weeks 2 and 8, LLLV was three times lower, percentage gain in weight was three times higher, bALP was 1.3 times lower and DPD was 1.5 times lower in the Dex group than the Pred group.

CONCLUSION

Pred and Dex both affect short-term growth and bone turnover. The mechanism of the effect on bone formation may be different between the two drugs. Dex may be about 18 times more potent than Pred at suppressing short-term linear growth and stimulating weight gain, and about nine times more potent at suppressing bone turnover. Glucocorticoids have a variable effect on different parameters of growth and bone turnover and the intensity may depend on the steroid used.

Congenital adrenal hyperplasia: 21-hydroxylase deficiency in the newborn and during infancy

Congenital adrenal hyperplasia is a family of monogenic autosomal recessive disorders of steroidogenesis with protean clinical manifestations. The commonest form, 21-hydroxylase deficiency, is the most frequent cause of ambiguous genitalia in the newborn. The molecular features associated with abnormalities in the CYP21 gene are well characterized in relation to phenotypic manifestations. The concordance between genotype and phenotype is sufficiently robust as to be relevant and useful in planning treatment strategies. Thus, the dose of glucocorticoid replacement in the early years of life can be tailored according to the predicted degree of 21-hydroxylase enzyme deficiency in the anticipation that this may avoid hitherto excessive steroid replacement during the critical early years of growth and development. The means to prevent genital virilization in affected females is clearly demonstrated by the success of early dexamethasone administration to pregnant mothers at risk. Short-term outcome studies of children exposed to dexamethasone in utero indicate no significant adverse effects. Nevertheless, it is recommended that prenatal treatment programs to prevent a major congenital malformation of the urogenital system be conducted only as part of agreed national multicenter studies, which include a commitment to long-term outcome analyses.

Evidence that luteinising hormone receptor polymorphisms may contribute to male undermasculinisation

BACKGROUND

The luteinising hormone receptor (LHR) is necessary for the stimulation of androgen production and male genital development. It contains three protein polymorphisms: a leucine and glutamine insertion between codons 8 and 9 (LQ+) and two amino acid substitutions (N291S, N312S).

OBJECTIVES

To determine whether these LHR polymorphisms are associated with male genital undermasculinisation or the androgen receptor polyglutamine repeat polymorphism (AR(Q)n), which contributes in some cases to the cause of genital undermasculinisation.

METHODS

The LHR polymorphisms were assessed by PCR amplification of genomic DNA, followed by restriction enzyme analysis. The frequency of the LHR polymorphisms were compared between an undermasculinised male group (n=75) and a control group (n=55).

RESULTS

LQ+ was not independently associated with the undermasculinised group (P=0.09), but it was associated with increased AR(Q)n within the undermasculinised group (P=0.02), particularly for AR(Q)n lengths >or=26 (P=0.002). In the undermasculinised group, homozygosity for N291 (872A/A) was more frequent (P=0.05), whereas homozygosity for N312 (935A/A) was less frequent (P=0.05). The combination of the presence of 872A/A and the absence of 935A/A showed a stronger association with the undermasculinised group than either polymorphism independently (P=0.006). The odds ratio of this genotype compared with any other, between the undermasculinised and control groups was 3.28 (95% confidence interval (CI) 1.33 to 8.08).

CONCLUSION

LHR polymorphisms may contribute to genital undermasculinisation.

Two de novo mutations in the AR gene cause the complete androgen insensitivity syndrome in a pair of monozygotic twins

The androgen insensitivity syndrome (AIS) is the most common cause of male undermasculinization and is typically caused by mutations in the AR gene. Affected individuals may exhibit either complete external feminization (complete AIS) or a partial phenotype (partial AIS). Here we describe monozygotic twins diagnosed with complete AIS who each possess two substitutions (C-->G at position 2930 and T-->C at position 2955, both in exon 7), leading to Phe(856)Leu and Ser(865)Pro mutations, respectively. Neither parent was found to be a carrier for these mutations, indicating that the double mutation arose de novo. Both mutations were recreated by site-directed mutagenesis and compared functionally with the wild-type receptor. The Phe(856)Leu mutation did not affect androgen binding when expressed in COS-1 cells, nor did this mutation decrease androgen-dependent trans-activation in transfected HeLa cells. However, the Ser(865)Pro mutation completely ablated androgen binding and trans-activation. In this study we demonstrate that the replacement of serine by proline at position 865 is sufficient in itself to cause complete AIS in these twins. Analyses of nuclear receptor structures suggest that this mutation is likely to perturb the conformation of helix 10/11, which plays a role in ligand binding, dimerization, and receptor activation. To our knowledge this is the first confirmed instance of AIS (complete or partial) due to an AR mutation occurring in twins. Furthermore, the phenotype was associated with two mutations that were both novel in nature.

The genetics of male undermasculinization

A review of the genetics of male undermasculinization must encompass a description of the embryology of the genital system. The dimorphism of sex development consequent upon the formation of a testis and the subsequent secretion of hormones to impose a male phenotype is highlighted. Thus, an understanding of the causes of male undermasculinization (manifest as XY sex reversal, complete and partial) includes reviewing the genetic factors which control testis determination and the production and action of testicular hormones. The study of disorders of male sex development has contributed substantially to knowledge of normal male development before birth. This knowledge has been complimented in recent years by the use of targeted murine gene disruption experiments to study the sex phenotype, although murine and human phenotypes are not always concordant. The investigation of disorders associated with male undermasculinization of prenatal onset is described briefly to complete the review.

Developmental aspects of androgen action

The formation of a testis from the indifferent gonad is the prelude to sequential steps in male sex differentiation orchestrated by time-dependent androgen biosynthesis and action. Information about the cellular and molecular mechanisms of androgen action can be obtained by the study of disorders of sex differentiation in males. The pivotal role of the androgen receptor as a ligand-induced transcription factor is emphasised and preliminary studies are described which attempt to identify developmentally regulated androgen-responsive genes. That androgen action can be modulated by gene polymorphisms is illustrated by the influence of an androgen receptor polyglutamine repeat in the multi-factorial causation of less severe forms of male under-masculinization.

Clinical and molecular evidence for the role of androgens and WT1 in testis descent

Testicular maldescent is a common congenital disorder associated with testicular cancer and infertility. In this study, testis position was assessed in subjects with genital abnormalities due to AR mutations, Denys-Drash and WAGR syndromes or an unknown aetiology. Subjects with completely female genitalia and an AR mutation or an unknown aetiology had a greater proportion of maldescended testes (intra-abdominal and inguinal) than those with less severe abnormalities (P=0.00027 and P<0.000001, respectively). Whereas subjects with severe, moderate or mild abnormalities and an unknown aetiology, had similar testis positions. The Denys-Drash and WAGR syndrome group had a greater proportion of maldescended testes than the AR mutation (P=0.013) and unknown aetiology groups (P=0.00019). Androgen production and AR binding were normal in three subjects with Denys-Drash and WAGR syndromes. These findings indicate that the relationship between testis descent and genital abnormalities is a multi-factorial process with greater complexity than previously proposed.

Autosomal recessive segregation of a truncating mutation of anti-Müllerian type II receptor in a family affected by the persistent Müllerian duct syndrome contrasts with its dominant negative activity in vitro

Anti-Müllerian hormone belongs to the TGFbeta family whose members exert their effects by signaling through two related serine/threonine kinase receptors. Mutations of the anti-Müllerian hormone type II receptor occur naturally, causing the persistent Müllerian duct syndrome. In a family with two members with persistent Müllerian duct syndrome and one normal sibling, we detected two novel mutations of the anti-Müllerian hormone type II receptor gene. One, transmitted by the mother to her three sons, is a deletion of a single base leading to a stop codon, causing receptor truncation after the transmembrane domain. The other, a missense mutation in the substrate-binding site of the kinase domain, is transmitted by the father to the two sons affected by persistent Müllerian duct syndrome, indicating a recessive autosomal transmission as in other cases of persistent Müllerian duct syndrome. Truncating mutations in receptors of the TGFbeta family exert dominant negative activity, which was seen only when each of the mutant anti-Müllerian hormone receptors was overexpressed in an anti-Müllerian hormone-responsive cell line. We conclude that assessment of dominant activity in vitro, which usually involves overexpression of mutant genes, does not necessarily produce information applicable to clinical conditions, in which mutant and endogenous genes are expressed on a one to one basis.

Minireview: sex differentiation

Mammalian sex differentiation is a hormone-dependent process in the male following the determination of a testis from the indifferent gonad through a cascade of genetic events. Female sex differentiation is not dependent on ovarian hormones, yet there is evidence that members of the Wnt family of developmental signaling molecules play a role in Müllerian duct development and in suppressing Leydig cell differentiation in the ovary. The testis induces male sex differentiation (including testis descent) through a time-dependent production of optimal concentrations of anti-Müllerian hormone, insulin-like factor(s) and androgens. Observations in several human syndromes of disordered fetal sex development corroborate findings in murine embryo studies, although there are exceptions in some gene knockout models. The ubiquitously expressed AR interacts in a ligand-dependent manner with coregulators to control the expression of androgen-responsive genes. Preliminary studies suggest the possibility of hormone resistance syndromes associated with coregulator dysfunction. Polymorphic variants in genes controlling androgen synthesis and action may modulate androgenic effects on sex differentiation.

Evidence that longer androgen receptor polyglutamine repeats are a causal factor for genital abnormalities

Moderate to severe undermasculinized genitalia was recently shown to be associated with longer polyglutamine repeats within the androgen receptor [AR(Gln)n]. However, it was unknown whether this was because longer AR(Gln)n contributed to the: 1) etiology; 2) severity; and/or 3) testicular maldescent. Therefore, AR(Gln)n length in 175 males with abnormal genitalia were analyzed according to etiology (known or unknown), severity (complete, severe, and moderate), or testis position (abdominal, inguinal, or scrotal). Etiology (P = 0.01) and severity (P = 0.02) but not testis position (P = 0.52) were associated with AR(Gln)n length. The association between the severity of the genital abnormalities and AR(Gln)n length was due to the close association of severity with the etiology (P < 0.0001). A highly selected group with moderate to severe genital abnormalities and multiple criteria to exclude known etiological factors had a greater AR(Gln)n length (mean, 25.33) than all other samples (mean, 23.11; P = 0.0004). The results suggest that AR(Gln)n length does not influence the severity of undermasculinization or testis descent but instead contributes to the causation of genital abnormalities in a subset of patients. These findings, together with a demonstrated relationship between severity and multifactorial etiology, are incorporated into a proposed model for the involvement of AR(Gln)n length in genital abnormalities.

Substitution mutation C268Y causes 17 beta-hydroxysteroid dehydrogenase 3 deficiency

The 17 beta-hydroxysteroid dehydrogenase (HSD) type 3 isozyme catalyzes the conversion of androstenedione to testosterone in the testis. Deleterious mutations in the HSD17B3 gene cause undermasculinization in genetic males attributable to impaired testosterone biosynthesis. Hence, a hallmark of this autosomal recessive disorder is a decreased plasma testosterone-to-androstenedione ratio. Here, a novel C268Y substitution mutation in exon 10 of the HSD17B3 gene, in a subject with 17 beta-HSD 3 deficiency, is reported. Reconstitution experiments with recombinant protein reveal that substitution of tyrosine for cysteine at position 268 of 17 beta-HSD type 3 abrogates the enzymatic activity. This finding brings to 20 the number of mutations in the HSD17B3 gene that cause male undermasculinization.

Genetic analysis of the INSL3 gene in patients with maldescent of the testis

OBJECTIVE

Testicular maldescent is important because it is a common congenital disorder that is associated with an increased risk of infertility and testicular cancer. Murine studies indicate that testicular maldescent can result from disruption of insulin-like factor 3 (INSL3) activity and that it may be more severe when there is concurrent undermasculinisation. Therefore, the INSL3 gene was screened for mutations and polymorphisms that may contribute to testicular maldescent in patients with undermasculinisation as well as those with isolated testicular maldescent.

METHODS AND RESULTS

The patient groups consisted of individuals with isolated testicular maldescent (n=28) and patients with undermasculinised genitalia and intra-abdominal (n=24) or inguinal gonads (n=33). The three control groups were: normal males (n=15), males with undermasculinised genitalia and scrotal gonads (n=29) and females (n=82). SSCP/HA mutation screening detected eight variants, five of which were predicted to alter the protein sequence (A-1G, V19L, P25S, A36T, R78H). Three of the amino acid changes (A-1G, V19L, R78H) each occurred in a single control sample and one was identified in a male with undermasculinised genitalia and intra-abdominal testes (P25S). The A36T amino acid polymorphism was found in both patient and control groups at a similar frequency.

CONCLUSIONS

The evidence suggests that INSL3 mutations and polymorphisms are not a major cause of testicular maldescent with or without associated undermasculinisation.