Novel Lethal Form of Congenital Hypopituitarism Associated With the First Recessive LHX4 Mutation

BACKGROUND

LHX4 encodes a member of the LIM-homeodomain family of transcription factors that is required for normal development of the pituitary gland. To date, only incompletely penetrant heterozygous mutations in LHX4 have been described in patients with variable combined pituitary hormone deficiencies.

OBJECTIVE/HYPOTHESIS

To report a unique family with a novel recessive variant in LHX4 associated with a lethal form of congenital hypopituitarism that was identified through screening a total of 97 patients.

METHOD

We screened 97 unrelated patients with combined pituitary hormone deficiency, including 65% with an ectopic posterior pituitary, for variants in the LHX4 gene using Sanger sequencing. Control databases (1000 Genomes, dbSNP, Exome Variant Server, ExAC Browser) were consulted upon identification of variants.

RESULTS

We identified the first novel homozygous missense variant (c.377C>T, p.T126M) in two deceased male patients of Pakistani origin with severe panhypopituitarism associated with anterior pituitary aplasia and posterior pituitary ectopia. Both were born small for gestational age with a small phallus, undescended testes, and mid-facial hypoplasia. The parents' first-born child was a female with mid-facial hypoplasia (DNA was unavailable). Despite rapid commencement of hydrocortisone and T4 in the brothers, all three children died within the first week of life. The LHX4(p.T126M) variant is located within the LIM2 domain, in a highly conserved location. The absence of homozygosity for the variant in over 65 000 controls suggests that it is likely to be responsible for the phenotype.

CONCLUSION

We report, for the first time to our knowledge, a novel homozygous mutation in LHX4 associated with a lethal phenotype, implying that recessive mutations in LHX4 may be incompatible with life.

Congenital hypopituitarism: clinical, molecular and neuroradiological correlates

OBJECTIVE

Recent studies have suggested that mutations in genes encoding several hypothalamo-pituitary (H-P) transcription factors result in hypopituitarism [isolated GH deficiency (IGHD) and combined pituitary hormone deficiency (CPHD)], which may in turn be related to the neuroanatomy revealed by magnetic resonance (MR) imaging. Although studies have focused on patients with either optic nerve hypoplasia (ONH) or isolated hypopituitarism with normal optic nerves, few studies have compared the two groups. We aimed to relate the clinical phenotype of a large cohort (n = 170) of children with congenital hypopituitarism including septo-optic dysplasia (SOD) attending a single centre to the neuroradiological and genetic findings.

DESIGN

Clinical, biochemical, MR imaging and molecular data were analysed retrospectively in 170 patients with or 'at-risk' (with ONH) of hypopituitarism to determine predictors of hypopituitarism.

RESULTS

The presence of ONH was significantly associated with an absent septum pellucidum [odds ratio (OR) 31.5, 95% confidence intervals (CI) 7.3-136.6, P < 0.001], an abnormal corpus callosum (OR 10.5, 95% CI 3.8-28.6, P < 0.001) and stalk abnormalities (OR 2.3, 95% CI 1.2-4.2, P = 0.009). The risk of hypopituitarism was 27.2 times greater in patients with an undescended posterior pituitary (95% CI 3.6-205.1, P < 0.001). Anterior pituitary hypoplasia (OR 3.1, 95% CI 1.3-7.0, P = 0.006) and an absent pituitary stalk (P < 0.001) were also significantly associated with hypopituitarism. With respect to the type or severity of hypopituitarism, CPHD was more often associated with an abnormal corpus callosum (OR 6.1, 95% CI 1.4-27.4, P = 0.008) and stalk abnormalities (OR 2.8, 95% CI 1.3-6.1, P = 0.006). Male to female ratio was significantly greater in patients with normal optic nerves (3.3:1) as compared with those with ONH (1.2:1). The prevalence of diabetes insipidus, thyrotrophin and ACTH deficiencies was significantly greater in patients with ONH as compared with 'idiopathic' hypopituitarism. Mutations in pituitary transcription factors and genes regulating GH secretion were rare (5/170) in this cohort of patients with sporadic hypopituitarism.

CONCLUSION

Our data suggest that individuals presenting with ONH are at high risk for neuroradiologic and endocrine abnormalities. The neuroradiologic features are predictive not only of the presence, but also of the type, of hypopituitarism. The association of midline abnormalities with hypopituitarism in this cohort suggests a common developmental origin for these features, the aetiology of which remains unidentified in the majority of cases.

Molecular analysis of novel PROP1 mutations associated with combined pituitary hormone deficiency (CPHD)

OBJECTIVE

Homozygous mutations in the gene encoding the pituitary transcription factor PROP1 are associated with combined pituitary hormone deficiency (CPHD) in both mice and humans with a highly variable phenotype with respect to the severity and time of initiation of pituitary hormone deficiency. We have ascertained three pedigrees with PROP1 mutations from a large cohort of patients with variable degrees of CPHD who were screened for mutations in PROP1.

RESULTS

Affected individuals from all three pedigrees were found to harbour novel PROP1 mutations. We have identified two siblings in one family who were homozygous for an intronic mutation (c.343-11C > G) that disrupts correct splicing resulting in the loss of exon 3 from the PROP1 transcript. Two siblings from a second, unrelated family are compound heterozygotes for two point mutations in the coding region, a missense mutation (p.R125W) that leads to impaired transcriptional activation, and a deletion of a single nucleotide (c.310delC) resulting in a frameshift and nonfunctional mutant protein. Additionally, we identified a homozygous deletion of the PROP1 locus in two patients born to consanguineous parents.

CONCLUSION

Mutations in PROP1 are a frequent cause of familial CPHD. We have described four novel mutations in PROP1 in 3 pedigrees, all resulting in PROP1 deficiency by different mechanisms. The phenotypic variation observed in association with PROP1 mutations both within and between families, together with the evolving nature of hormone deficiencies and sometimes changing pituitary morphology indicates a need for continual monitoring of these patients.

Evolution of gonadotropin deficiency in a patient with type II autosomal dominant GH deficiency

BACKGROUND

Type II isolated GH deficiency (IGHD type II) is caused by dominant negative splicing or point mutations of the GH-1 gene. Studies have suggested that dominant mutant GH forms prevent the secretion of wild-type GH, resulting in eventual cell death; surprisingly, some patients with these GH mutations develop other hormonal deficiencies (ACTH, TSH).

SUBJECTS

The proband presented at the age of 2.3 years with IGHD. His father, also known to have been treated for IGHD as a child, had subsequently been lost to follow-up, having remained without treatment during this time. At re-evaluation at the age of 38 years, he complained of lack of stamina and poor libido. Clinical and biochemical assessment confirmed severe GHD, borderline ACTH insufficiency, suboptimal basal and stimulated gonadotropins, and a poor prolactin response to provocation. The basal testosterone concentration was low, and he complained of secondary infertility. Magnetic resonance imaging revealed anterior pituitary hypoplasia in both patients. Genetic testing revealed a heterozygous splicing mutation in GH-1 (intervening sequence-3 + 1G>A) in both patients, known to cause IGHD type II.

INTERVENTIONS

The proband showed an excellent growth response to recombinant human GH (rhGH). His father, also treated with rhGH, showed improved quality of life on rhGH, but testosterone concentrations continued to decline, necessitating treatment with testosterone with symptomatic benefit but no improvement in semen quality.

CONCLUSIONS

This case supports recent experimental and clinical observations suggesting that the cytotoxicity associated with accumulation of dominant negative mutant 17.5 kDa GH causes a form of GHD that can evolve into multiple hormone deficiencies. Hence, patients diagnosed initially with IGHD type II require continued long-term clinical follow-up.

Novel mutations within the POU1F1 gene associated with variable combined pituitary hormone deficiency

CONTEXT

Mutations within the gene encoding the pituitary-specific transcription factor POU1F1 are associated with combined pituitary hormone deficiency (CPHD). Most of the affected individuals manifest GH, prolactin, and TSH deficiency.

OBJECTIVE

We have now screened 129 individuals with CPHD and isolated GH deficiency for mutations within POU1F1.

RESULTS

Causative mutations were identified in 10 of 129 individuals (7.8%). Of these, five patients harbored the dominant negative R271W mutation, which is a well-recognized mutational hot spot. We have also identified a second frequently occurring mutation, E230K, which appears to be common in Maltese patients. Additionally, we describe two novel mutations within POU1F1, an insertion of a single base pair (ins778A) and a missense mutation (R172Q). Functional studies have revealed that POU1F1 (E230K) is associated with a reduction in transactivation, although DNA-binding affinity is similar to the wild-type protein. On the other hand, POU1F1 (R172Q) is associated with a reduction in DNA binding and transactivation, whereas POU1F1 (ins778A) is associated with loss of DNA binding and a reduction in transactivation.

CONCLUSIONS

Our data suggest that the phenotype associated with POU1F1 mutations may be more variable, with the occasional preservation of TSH secretion. Additionally, our data revealed POU1F1 mutations in three patients who were diagnosed as having ACTH deficiency but who, on further evaluation, were found to have normal cortisol secretion. Hence, elucidation of the genotype led to further evaluation of the phenotype, with the cessation of cortisol replacement that had been commenced unnecessarily. These data reflect the importance of mutational analysis in patients with CPHD.

The role of growth hormone in determining birth size and early postnatal growth, using congenital growth hormone deficiency (GHD) as a model

OBJECTIVE

The role of GH in early human growth is unclear. Congenital GH deficiency (CGHD) provides a useful tool to explore this putative role. We have assessed the effects of CGHD on birth size and early postnatal growth, and the further impact of the presence of additional pituitary hormone deficiencies and midline brain defects on these parameters.

DESIGN, PATIENTS AND MEASUREMENTS

Weight, length and BMI expressed as standard deviation scores (SDS), over the first two years of life, were retrospectively compared in 44 GH-deficient children (M:F 26 : 18). Thirty-eight of 44 patients underwent GH provocation testing and all patients had neuro-imaging of the brain. The patients were divided into three groups of increasing phenotypic complexity {group A [n = 12, isolated GHD, no midline defects], group B [n = 10, combined pituitary hormone deficiency (CPHD); no midline defects], group C (n = 22, CPHD with midline defects)}.

RESULTS

Mean birth weight, length and BMI SDS were -0.4, -0.9 and +0.1 SDS, respectively. The differences were significant for weight (P = 0.03) and BMI (P = 0.003), but not length (P = 0.3) SDS, between groups A and C. Of the three groups, group A had a lower weight and BMI SDS than group C. The prevalence of postnatal complications (n = 25) was significantly different in the three groups [group A (8%), group B (80%), group C (73%); P < 0.001] and particularly between patients with isolated GH deficiency (IGHD) (group A) and CPHD (groups B and C; P < 0.0001). No patients in group A presented with neonatal hypoglycaemia as compared with 70% of those in group B and 59% in group C (P = 0.001). A reduced length SDS was observed in all patients within 6 months of birth and the reduction was greatest in group B (P = 0.03). Group C remained significantly (P < 0.05) heavier at 12, 18 and 24 months compared to group A. BMI SDS was significantly (P < 0.05) greater at all study points in CPHD patients (groups B and C) as compared with IGHD. Serum GH concentrations at testing did not correlate significantly with birth length (r = -0.08, P = 0.7), birth weight (r = -0.08, P = 0.6) or the age at induction of GH treatment (r = 0.12, P = 0.5). There were no significant differences between peak serum GH concentrations in patients in groups A (7.8 +/- 6.3 mU/l), B (3.9 +/- 4.8 mU/l) or C (8.7 +/- 5.4 mU/l).

CONCLUSIONS

Length, weight and BMI data from our study groups suggest that GH per se has a minimal effect on intrauterine growth but a significant effect during the infancy period. Early growth may also be influenced by the complexity of the hypopituitary phenotype reflected by the presence of additional pituitary hormone deficiencies and midline forebrain defects.

Mutations within the transcription factor PROP1 are rare in a cohort of patients with sporadic combined pituitary hormone deficiency (CPHD)

OBJECTIVE

Mutations within the pituitary-specific paired-like homeobox gene PROP1 have been described in 50-100% of patients with familial combined pituitary hormone deficiency (CPHD). We screened a cohort of sporadic (n = 189) and familial (n = 44) patients with hypopituitarism (153 CPHD and 80 isolated hormone deficiencies) for mutations within the coding sequence of PROP1.

DESIGN AND PATIENTS

Patients with congenital hypopituitarism were recruited from the London Centre for Paediatric Endocrinology as well as several national and international centres. The pituitary phenotype ranged from isolated growth hormone deficiency (IGHD) to panhypopituitarism. Clinical data, including endocrine and neuro-radiological studies were obtained from patient records, and DNA was collected and screened for mutations within PROP1 using PCR and single-stranded conformation polymorphism (SSCP) analysis. Positive results on SSCP were sequenced directly.

RESULTS

The prevalence of PROP1 mutations in unselected sporadic cases of hypopituitarism was lower (1.1%) than in familial cases (29.5%). PROP1 mutations can be associated with a highly variable phenotype, and both pituitary hypoplasia and pituitary hyperplasia. We describe the waxing and waning of a pituitary mass over 20 months in association with a PROP1 mutation that is predicted to lead to complete loss of function. Additionally, we have identified a possible founder mutation in CPHD patients from the Indian subcontinent.

CONCLUSIONS

PROP1 mutations are rare in sporadic cases of CPHD, although the prevalence rises if there is a positive family history or if the patients are carefully selected with respect to the endocrine and neuroradiological phenotype. There is considerable phenotypic variability in families with the same mutation, indicating the role of other genetic or environmental factors on phenotypic expression. Finally, the pituitary enlargement that is observed in patients with PROP1 mutations can wax and wane in size before eventual involution.