The phenotypic spectrum associated with OTX2 mutations in humans.

Objective: The transcription factor OTX2 is implicated in ocular, craniofacial, and pituitary development. Design: We aimed to establish the contribution of OTX2 mutations in congenital hypopituitarism patients with/without eye abnormalities, study functional consequences, and establish OTX2 expression in the human brain, with a view to investigate the mechanism of action. Methods: We screened patients from the UK (n = 103), international centres (n = 24), and Brazil (n = 282); 145 were within the septo-optic dysplasia spectrum, and 264 had no eye phenotype. Transactivation ability of OTX2 variants was analysed in murine hypothalamic GT1-7 neurons. In situ hybridization was performed on human embryonic brain sections. Genetically engineered mice were generated with a series of C-terminal OTX2 variants. Results: Two chromosomal deletions and six haploinsufficient mutations were identified in individuals with eye abnormalities; an affected relative of one patient harboured the same mutation without an ocular phenotype. OTX2 truncations led to significant transactivation reduction. A missense variant was identified in another patient without eye abnormalities; however, studies revealed it was most likely not causative. In the mouse, truncations proximal to aa219 caused anophthalmia, while distal truncations and the missense variant were tolerated. During human embryogenesis, OTX2 was expressed in the posterior pituitary, retina, ear, thalamus, choroid plexus, and partially in the hypothalamus, but not in the anterior pituitary. Conclusions: OTX2 mutations are rarely associated with hypopituitarism in isolation without eye abnormalities, and may be variably penetrant, even within the same pedigree. Our data suggest that the endocrine phenotypes in patients with OTX2 mutations are of hypothalamic origin.

FGFR1 and PROKR2 rare variants found in patients with combined pituitary hormone deficiencies.

The genetic aetiology of congenital hypopituitarism (CH) is not entirely elucidated. FGFR1 and PROKR2 loss-of-function mutations are classically involved in hypogonadotrophic hypogonadism (HH), however, due to the clinical and genetic overlap of HH and CH; these genes may also be involved in the pathogenesis of CH. Using a candidate gene approach, we screened 156 Brazilian patients with combined pituitary hormone deficiencies (CPHD) for loss-of-function mutations in FGFR1 and PROKR2. We identified three FGFR1 variants (p.Arg448Trp, p.Ser107Leu and p.Pro772Ser) in four unrelated patients (two males) and two PROKR2 variants (p.Arg85Cys and p.Arg248Glu) in two unrelated female patients. Five of the six patients harbouring the variants had a first-degree relative that was an unaffected carrier of it. Results of functional studies indicated that the new FGFR1 variant p.Arg448Trp is a loss-of-function variant, while p.Ser107Leu and p.Pro772Ser present signalling activity similar to the wild-type form. Regarding PROKR2 variants, results from previous functional studies indicated that p.Arg85Cys moderately compromises receptor signalling through both MAPK and Ca(2) (+) pathways while p.Arg248Glu decreases calcium mobilization but has normal MAPK activity. The presence of loss-of-function variants of FGFR1 and PROKR2 in our patients with CPHD is indicative of an adjuvant and/or modifier effect of these rare variants on the phenotype. The presence of the same variants in unaffected relatives implies that they cannot solely cause the phenotype. Other associated genetic and/or environmental modifiers may play a role in the aetiology of this condition.

Frequent development of combined pituitary hormone deficiency in patients initially diagnosed as isolated growth hormone deficiency: a long term follow-up of patients from a single center.

BACKGROUND: Children initially diagnosed with isolated GH deficiency (IGHD) have a variable rate to progress to combined pituitary hormone deficiency (CPHD) during follow-up. OBJECTIVE: To evaluate the development of CPHD in a group of childhood-onset IGHD followed at a single tertiary center over a long period of time. PATIENTS AND METHODS: We retrospectively analyzed data from 83 patients initially diagnosed as IGHD with a mean follow-up of 15.2 years. The Kaplan-Meier method and Cox regression analysis was used to estimate the temporal progression and to identify risk factors to development of CPHD over time. RESULTS: From 83 patients initially with IGHD, 37 (45%) developed CPHD after a median time of follow up of 5.4 years (range from 1.2 to 21 years). LH and FSH deficiencies were the most common pituitary hormone (38%) deficiencies developed followed by TSH (31%), ACTH (12%) and ADH deficiency (5%). ADH deficiency (3.1 ± 1 years from GHD diagnosis) presented earlier and ACTH deficiency (9.3 ± 3.5 years) presented later during follow up compared to LH/FSH (8.3 ± 4 years) and TSH (7.5 ± 5.6 years) deficiencies. In a Cox regression model, pituitary stalk abnormalities was the strongest risk factor for the development of CPHD (hazard ratio of 3.28; p = 0.002). CONCLUSION: Our study indicated a high frequency of development of CPHD in patients initially diagnosed as IGHD at childhood. Half of our patients with IGHD developed the second hormone deficiency after 5 years of diagnosis, reinforcing the need for lifelong monitoring of pituitary function in these patients.

Pituitary magnetic resonance imaging and function in patients with growth hormone deficiency with and without mutations in GHRH-R, GH-1, or PROP-1 genes.

Pituitary stalk interruption and ectopic posterior lobe on magnetic resonance imaging (MRI) are frequently observed in patients with GH deficiency (GHD), but their pathogenesis remains controversial. We performed pituitary stimulation tests, MRI, and studied GH-1, GHRH receptor (GHRH-R), and Prophet of Pit-1 (PROP-1) genes in 76 patients with GHD. Of 33 patients with isolated GHD, 4 had GH-1 deletions and 4 had GHRH-R mutations; of 43 patients with combined pituitary hormone deficiency, 1 had PIT-1 and 5 had PROP-1 mutations. Compared with the 62 patients without mutations, 14 patients with mutations had higher frequency of consanguinity (57 vs. 2%, P < 0.001), familial cases (21 vs. 3%, P < 0.05), and lower frequency of breech delivery or hypoxemia at birth (0 vs. 39%, P < 0.005). On MRI, all patients with mutations had an intact stalk, whereas it was interrupted or thin in 74% without mutations (P < 0.001). The posterior pituitary lobe was in normal position in 92% of patients with mutations against 13% without mutations (P < 0.001). Among patients with combined pituitary hormone deficiency, hormonal deficiencies were of pituitary origin in all with PROP-1 and PIT-1 mutations and suggestive of hypothalamic origin in 81% without mutations. Perinatal insults were associated with thin/interrupted pituitary stalk, ectopic posterior lobe, and hypothalamic origin of hormonal deficiencies. In contrast, GH-1, GHRH-R, and PROP-1 mutations were associated with consanguineous parents, intact pituitary stalk, normal posterior lobe, and pituitary origin of hormonal deficiencies. We conclude that pituitary MRI and hormonal response to stimulation tests are useful in selection of patients and candidate genes to elucidate the etiological diagnosis of GHD.