Childhood growth of females with Kallmann syndrome and FGFR1 mutations

OBJECTIVE

In search of phenotypic cues that would allow early detection of Kallmann syndrome (KS), we evaluated the paediatric phenotypes in a series of females with KS.

DESIGN, PATIENTS AND MEASUREMENTS

In this retrospective cohort study, we investigated childhood growth in six females with KS due to mutations in FGFR1 and evaluated their reproductive phenotypes later in life.

RESULTS

While growth during early infancy and childhood was within normal limits, a decreasing trend in height SDS already from mid-childhood occurred in most patients. The lowest height SDS (mean, -1·2 SDS) occurred between 14 and 15 years of age, before the start of hormone replacement therapy. As adults, these women required assisted reproductive techniques for fertility. One of the probands passed on her G48S mutation to her son, who showed normal reproductive hormone levels during the minipuberty of infancy.

CONCLUSIONS

Early diagnosis of female KS remains a challenge as early phenotypic signs, apart from anosmia, are scarce. Females with KS exhibit a slight reduction in growth rate during mid-childhood, but normal growth rate during the minipuberty of infancy, despite congenital lack of ovarian oestrogen. Women harbouring FGFR1 mutations will have 50% chance of passing on the gene defect to their offspring. We recommend genetic counselling to all females with KS to be carried out as a part of family planning.

Mutation screening of SEMA3A and SEMA7A in patients with congenital hypogonadotropic hypogonadism

BACKGROUND

Congenital hypogonadotropic hypogonadism (HH), a rare disorder characterized by absent, partial, or delayed puberty, can be caused by the lack or deficient number of hypothalamic gonadotropin-releasing hormone (GnRH) neurons. SEMA3A was recently implicated in the etiology of the disorder, and Sema7A-deficient mice have a reduced number of GnRH neurons in their brains.

METHODS

SEMA3A and SEMA7A were screened by Sanger sequencing in altogether 50 Finnish HH patients (34 with Kallmann syndrome (KS; HH with hyposmia/anosmia) and 16 with normosmic HH (nHH)). In 20 patients, mutation(s) had already been found in genes known to be implicated in congenital HH.

RESULTS

Three heterozygous variants (c.458A>G (p.Asn153Ser), c.1253A>G (p.Asn418Ser), and c.1303G>A (p.Val435Ile)) were found in SEMA3A in three KS patients, two of which also had a mutation in FGFR1. Two rare heterozygous variants (c.442C>T (p.Arg148Trp) and c.1421G>A (p.Arg474Gln)) in SEMA7A were found in one male nHH patient with a previously identified KISS1R nonsense variant and one male KS patient with a previously identified mutation in KAL1, respectively.

CONCLUSION

Our results suggest that heterozygous missense variants in SEMA3A and SEMA7A may modify the phenotype of KS but most likely are not alone sufficient to cause the disorder.

Circulating antimüllerian hormone levels in boys decline during early puberty and correlate with inhibin B

OBJECTIVE

To investigate peripheral levels of inhibin B and antimüllerian hormone (AMH) in boys during peripuberty and in patients with congenital hypogonadotropic hypogonadism (HH).

DESIGN

Randomized, placebo-controlled trial (peripubertal boys); and cross-sectional clinical study (males with HH).

SETTING

University central hospital.

PATIENT(S)

Twenty-eight peripubertal boys with idiopathic short stature (ISS), 19 males with Kallmann syndrome.

INTERVENTION(S)

Letrozole (2.5 mg/day) or placebo in boys with ISS for 2 years.

MAIN OUTCOME MEASURE(S)

Longitudinal follow-up observation of serum AMH and its relationship with inhibin B during early puberty and the influence of high (letrozole-treated boys) and low (males with HH) gonadotropin exposure on circulating AMH.

RESULT(S)

In boys with ISS receiving placebo, the decrease in AMH levels and the increase in inhibin B levels were correlated. The serum AMH level had already declined before a clinically significant increase in testis volume or serum testosterone occurred. Letrozole did not appear to modulate the decline in AMH. The AMH levels were lower in boys and young adults with Kallmann syndrome and prepubertal testes (mean: 20.9 ± 4.7 ng/mL, n = 6) as compared with prepubertal ISS boys (102.3 ± 11.9 ng/mL).

CONCLUSION(S)

The gonadotropin-mediated early pubertal increase in inhibin B is tightly coupled to decrease in AMH levels and may reflect androgen-mediated differentiation of Sertoli cells. Profound gonadotropin deficiency is associated with low AMH levels, suggesting impaired development of the Sertoli cell population.

Isolated cryptorchidism: no evidence for involvement of genes underlying isolated hypogonadotropic hypogonadism

Mutations in FGFR1, GNRHR, PROK2, PROKR2, TAC3, or TACR3 underlie isolated hypogonadotropic hypogonadism (IHH) with clinically variable phenotypes, and, by causing incomplete intrauterine activation of the hypothalamic-pituitary-gonadal axis, may lead to cryptorchidism. To investigate the role of defects in these genes in the etiology of isolated cryptorchidism, we screened coding exons and exon-intron boundaries of these genes in 54 boys or men from 46 families with a history of cryptorchidism. Control subjects (200) included 120 males. None of the patients carried mutation(s) in FGFR1, PROK2, PROKR2, TAC3 or TACR3. Two of the 46 index subjects with unilateral cryptorchidism were heterozygous carriers of a single GNRHR mutation (Q106R or R262Q), also present in male controls with a similar frequency (3/120; p=0.62). No homozygous or compound heterozygous GNRHR mutations were found. In conclusion, cryptorchidism is not commonly caused by defects in genes involved in IHH.

Incidence, phenotypic features and molecular genetics of Kallmann syndrome in Finland

Background

Kallmann syndrome (KS), comprised of congenital hypogonadotropic hypogonadism (HH) and anosmia, is a clinically and genetically heterogeneous disorder. Its exact incidence is currently unknown, and a mutation in one of the identified KS genes has only been found in ~30% of the patients.

Methods

Herein, we investigated epidemiological, clinical, and genetic features of KS in Finland.

Results

The minimal incidence estimate of KS in Finland was 1:48 000, with clear difference between males (1:30 000) and females (1:125 000) (p = 0.02). The reproductive phenotype of 30 probands (25 men; 5 women) ranged from severe HH to partial puberty. Comprehensive mutation analysis of all 7 known KS genes (KAL1, FGFR1, FGF8, PROK2, PROKR2, CHD7, and WDR11) in these 30 well-phenotyped probands revealed mutations in KAL1 (3 men) and FGFR1 (all 5 women vs. 4/25 men), but not in other genes.

Conclusions

Our results suggest that Finnish KS men harbor mutations in gene(s) yet-to-be discovered with sex-dependent penetrance of the disease phenotype. In addition, some KS patients without CHD7 mutations display CHARGE-syndrome associated phenotypic features (e.g. ear or eye anomalies), possibly implying that, in addition to CHD7, there may be other genes associated with phenotypes ranging from KS to CHARGE.

The role of gene defects underlying isolated hypogonadotropic hypogonadism in patients with constitutional delay of growth and puberty

Variation in FGFR1, GNRHR, TAC3, and TACR3 was evaluated in 146 Finnish subjects with constitutional delay of growth and puberty. Although one male subject carried a previously undescribed heterozygous deletion (Phe309del) in GNRHR, which segregated with delayed puberty in his family, mutations in the coding regions of FGFR1, GNRHR, TAC3, and TACR3 are not likely to underlie common constitutional delay of growth and puberty.

LIN28B in constitutional delay of growth and puberty

BACKGROUND

Recently variation in LIN28B, a human ortholog of the gene-regulating processing of micro-RNAs (miRNAs) controlling the timing of major developmental events in the nematode Caenorhabditis elegans, was reported to be associated with timing of puberty in humans. In C. elegans, a gain-of-function allele of lin-28 causes a retarded phenotype.

OBJECTIVE

The objective of the study was to evaluate the variation in the LIN28B gene in 145 subjects with constitutional delay of growth and puberty (CDGP).

PATIENTS AND METHODS

For this study, 115 males and 30 females with CDGP were included. CDGP was defined by Tanner genital or breast stage II and pubertal growth spurt taking place 2 SD later than average. The four coding exons (exons 1-4) and exon-intron boundaries, as well as the fragment of 3' untranslated region containing miRNA recognition elements A and B, of LIN28B were PCR amplified from genomic DNA obtained from peripheral blood leukocytes of the subjects and bidirectionally sequenced.

RESULTS

No variation in the coding region of LIN28B in the 145 subjects with CDGP was found. However, 16 of 145 subjects carried a 2-nucleotide deletion immediately 5' from miRNA recognition element A. These patients did not differ in phenotypic features as compared with noncarriers, and this variant was present in 100 controls with the same frequency.

CONCLUSIONS

Our results show that mutations in the coding region or 3' untranslated region miRNA recognition elements A and B of LIN28B do not underlie CDGP. Lack of any variation in the coding region of the gene suggests that LIN28B in developmental timing is so crucial that any changes in the conserved protein would probably be lethal.