Céline Huot

Decreased FGF8 signaling causes deficiency of gonadotropin-releasing hormone in humans and mice

Idiopathic hypogonadotropic hypogonadism (IHH) with anosmia (Kallmann syndrome; KS) or with a normal sense of smell (normosmic IHH; nIHH) are heterogeneous genetic disorders associated with deficiency of gonadotropin-releasing hormone (GnRH). While loss-of-function mutations in FGF receptor 1 (FGFR1) cause human GnRH deficiency, to date no specific ligand for FGFR1 has been identified in GnRH neuron ontogeny. Using a candidate gene approach, we identified 6 missense mutations in FGF8 in IHH probands with variable olfactory phenotypes. These patients exhibited varied degrees of GnRH deficiency, including the rare adult-onset form of hypogonadotropic hypogonadism. Four mutations affected all 4 FGF8 splice isoforms (FGF8a, FGF8b, FGF8e, and FGF8f), while 2 mutations affected FGF8e and FGF8f isoforms only. The mutant FGF8b and FGF8f ligands exhibited decreased biological activity in vitro. Furthermore, mice homozygous for a hypomorphic Fgf8 allele lacked GnRH neurons in the hypothalamus, while heterozygous mice showed substantial decreases in the number of GnRH neurons and hypothalamic GnRH peptide concentration. In conclusion, we identified FGF8 as a gene implicated in GnRH deficiency in both humans and mice and demonstrated an exquisite sensitivity of GnRH neuron development to reductions in FGF8 signaling.

Mutations in Prokineticin 2 and Prokineticin receptor 2genes in Human Gonadotrophin-Releasing Hormone Deficiency: Molecular Genetics and Clinical Spectrum

CONTEXT Mice deficient in prokineticin 2(PROK2) and prokineticin receptor2 (PROKR2) exhibit variable olfactory bulb dysgenesis and GnRH neuronal migration defects reminiscent of human GnRH deficiency. OBJECTIVES We aimed to screen a large cohort of patients with Kallmann syndrome (KS) and normosmic idiopathic hypogonadotropic hypogonadism (IHH) for mutations in PROK2/PROKR2, evaluate their prevalence, define the genotype/phenotype relationship, and assess the functionality of these mutant alleles in vitro. DESIGN Sequencing of the PROK2 and PROKR2 genes was performed in 170 KS patients and 154 nIHH. Mutations were examined using early growth response 1-luciferase assays in HEK 293 cells and aequorin assays in Chinese hamster ovary cells. RESULTS Four heterozygous and one homozygous PROK2 mutation (p.A24P, p.C34Y, p.I50M, p.R73C, and p.I55fsX1) were identified in five probands. Four probands had KS and one nIHH, and all had absent puberty. Each mutant peptide impaired receptor signaling in vitro except the I50M. There were 11 patients who carried a heterozygous PROKR2 mutation (p.R85C, p.Y113H, p.V115M, p.R164Q, p.L173R, p.W178S, p.S188L, p.R248Q, p.V331M, and p.R357W). Among them, six had KS, four nIHH, and one KS proband carried both a PROKR2 (p.V115M) and PROK2 (p.A24P) mutation. Reproductive phenotypes ranged from absent to partial puberty to complete reversal of GnRH deficiency after discontinuation of therapy. All mutant alleles appear to decrease intracellular calcium mobilization; seven exhibited decreased MAPK signaling, and six displayed decreased receptor expression. Nonreproductive phenotypes included fibrous dysplasia, sleep disorder, synkinesia, and epilepsy. Finally, considerable variability was evident in family members with the same mutation, including asymptomatic carriers. CONCLUSION Loss-of-function mutations in PROK2 and PROKR2 underlie both KS and nIHH.

Severe congenital hypopituitarism with low prolactin levels and age-dependent anterior pituitary hypoplasia: A clue to a PIT-1 mutation

A 20-month-old boy presented with severe congenital growth hormone, thyrotropin, and prolactin deficiencies resulting from a de novo mutation of the PIT-1 gene. This form of congenital hypopituitarism should be suspected if pituitary anatomy is normal, especially if prolactin levels are low and, in boys, if the external genitalia are normal. Pituitary atrophy appears to be an age-dependent phenomenon in this condition.

Outcome in three siblings with antibody-mediated transient congenital hypothyroidism

A woman receiving thyroxine substitution therapy for acquired hypothyroidism caused by autoimmune thyroiditis gave birth to three babies who had transient primary hypothyroidism. All three babies had elevated thyrotropin levels on neonatal screening, but one had normal thyroxine values. Thyrotropin receptor-blocking antibodies were present in maternal serum and in the three neonates. Each baby also had a different congenital malformation. The neurodevelopmental outcome of the children appeared related in part to maternal thyroxine levels, which suggests that transplacental transfer of thyroxine may protect the fetal brain.

Comparison of Adolescents with Klinefelter Syndrome according to the Circumstances of Diagnosis: Amniocentesis versus Clinical Signs

Aims: We compared the phenotype of adolescents with Klinefelter syndrome diagnosed by amniocentesis or postnatally to the general population with a view to evidence-based genetic counselling. Methods: The charts of 28 patients seen between ages 12 and 18 years were reviewed. Physical and neurodevelopmental data were compared between patients diagnosed by chance (amniocentesis, group A, n = 11) or on the basis of symptoms (group B, n = 17) and the general population. Our hypothesis was that group A would have a more heterogeneous and less severe phenotype than group B. Results: All patients had spontaneous puberty. The 2 patient groups were similar in physical development. Mean testosteronemia became lower than the normal mean from age 14 years. Compared to the general population, the prevalence of gynecomastia and school delay in group A was not significantly different (gynecomastia 33 vs. 40%, p = 0.70; school delay 40 vs. 20%, p = 0.25). In contrast, gynecomastia (77%) and school delay (56%) were significantly more frequent in group B than in the general population (p = 0.01 for both). Conclusions: Although they are based on a small number of patients, our data provide the groundwork for cautious optimism in prenatal counselling for Klinefelter syndrome.

Is Ultrasonography Useful in Predicting Thyroid Cancer in Children with Thyroid Nodules and Apparently Benign Cytopathologic Features

Background/Aims: To assess whether the presence of certain findings on thyroid ultrasonography (US) correctly diagnoses malignancy even when a fine-needle aspiration biopsy (FNAB) suggests a benign lesion. Methods: We reviewed the charts of 35 children and adolescents with a thyroid nodule who had had an US and a FNAB, and for whom final pathology was available. Results: The global accuracy of FNAB was 83%, with a sensitivity of 75% and a specificity of 94%. 14 FNABs suggested malignancy (40%), only 1 of which was a false positive (7%). By contrast, 5 of the 21 FNABs suggesting benign lesions were false negatives (24%). These 5 cases had US findings suggestive of malignancy. When FNAB suggested a benign lesion, US had a good sensitivity (80%) but a poor specificity and accuracy (50 and 57%, respectively); its negative predictive value was 90% and its positive predictive value 36%. Conclusions: US complements FNAB in the evaluation of thyroid nodules in children. A more aggressive approach is warranted in children with a thyroid nodule and a benign FNAB if US findings suggest malignancy.

Thyroid scintigraphy in children and adolescents with Hashimoto disease

Between 1989 and 1994, 58 children and adolescents with Hashimoto thyroiditis seen at the Sainte-Justine Hospital had thyroid scintigraphy. Their medical records and films were reviewed retrospectively. Eighty-nine percent of the patients had a homogeneous distribution of tracer on thyroid scintigraphy, unlike the heterogeneous distribution classically reported in adults. In children and adolescents, thyroid scintigraphy is not helpful in the diagnosis of typical Hashimoto thyroiditis.

Severe Cortisol Deficiency Associated with Reversible Growth Hormone Deficiency in Two Infants: What Is the Link?

CONTEXT Hypoglycemia is potentially life-threatening, especially in infants, and can be due to congenital cortisol and/or GH deficiency (GHD). CASE ILLUSTRATION Two full-term infants had undetectable cortisol levels, but also low GH levels, at the time of severe hypoglycemia. GHD persisted for several months, even after cortisol replacement. METHODS Targeted molecular investigations were performed and revealed homozygous inactivating mutations in MRAP (MIM ID 609196) in patient 1 and in TPIT (MIM ID 604614) in patient 2. Because GHD is not part of the MRAP or TPIT phenotypes, we performed GH stimulation tests. These revealed that GHD had resolved by 8 months (patient 1) and 3 yr (patient 2) of glucocorticoid replacement. GH replacement was therefore stopped, hypoglycemia did not recur, and over the subsequent 10 yr, growth and puberty have proceeded normally. CONCLUSIONS 1) Physiological glucocorticoid levels appear to be required for the development and function of the somatotrophs during infancy. 2) Eucortisolism, like euthyroidism, is required for the proper evaluation of GH secretory capacity. 3) The metabolic effect of GH replacement is essential for the maintenance of normoglycemia, especially in infants. And 4) targeted molecular investigations are a powerful tool to clarify the diagnosis in severely ill infants and to reevaluate the specific treatment they need.

Impact of Patient Characteristics and Clinical Factors on the Decision to Initiate Growth Hormone Treatment in Turner Syndrome

Background/Aims: To evaluate factors contributing to the decision to initiate treatment with growth hormone (GH) in patients with Turner syndrome (TS). Methods: Data collected included ethnicity, parents’ education and work status, mid-parental height, age at diagnosis, karyotype, pubertal development, clinical severity score, bone age, height SDS and ages when GH was proposed and initiated. Results: GH was proposed to 59 of 72 patients >6 years (82%), and of these 46 (78%) accepted. Reasons for not proposing GH included late diagnosis, good growth and loss to follow-up. GH-treated and untreated girls differed by age at diagnosis (mean ± SD: 6.8 ± 4.7 vs. 4.3 ± 5.1 years; p = 0.04), TS-specific height SDS (0.08 ± 0.81 vs. 066 ± 0.87; p = 0.01) and spontaneous puberty (5/46 vs. 4/26, p = 0.024). Mean age at which it was suggested to begin GH was 9.2 ± 2.9 years. Reasons for parental refusal of GH were not related to reimbursement issues since GH treatment is covered fully by our insurance plan but included concern with other medical issues, mental health problems and fear of injections or unknown side effects. Conclusion: GH treatment was not acceptable to all patients with TS.

Premature Ovarian Failure in French Canadian Leigh Syndrome

In all surviving girls with Leigh syndrome, French Canadian variety, a mitochondrial disease, we detected premature ovarian failure, manifested as absent or arrested breast development, lack of menarche, high follicle-stimulating hormone, a prepubertal uterus, and small ovaries. Pubertal onset and progression should be evaluated in girls with mitochondrial diseases.