Short stature is one of the most common presentations in the pediatric endocrinology clinics [1]. Growth is affected by multiple factors such as nutrition, genetic, metabolic and environmental factors. Among these factors growth hormone deficiency (GHD) and congenital hypopituitarism are rare causes of childhood short stature [2]. Combined pituitary hormone deficiency (CPHD) has an incidence of approximately 1:8000 births and 5-30 % of cases are familial [3]. Normal pituitary development and differentiation occur as a result of the combination of many transcription factors, encoded by the genes HESX1, LHX3, LHX4, PROP1, and POU1F1[4]. POU1F1 was the first pituitary specific transcription factor to be identified in 1988 by Bodner et al and referred to as Pit-1[5]. In 1992, Ohta [6] localized the human PIT-1 gene to 3p11. POU1F1 is restricted to the anterior pituitary and is also essential for the differentiation of somatotrophs, lactotrophs and thyrotrophs [7]. POU1F1 variants accounts for 0.4-20% in genetic causes of CPHD and lead to GHD, central hypothyroidism and hypoprolactinemia [2]. Neuroimaging usually shows normal or hypoplastic anterior pituitary with preserved pituitary stalk and posterior pituitary [8]. Herein, we report two siblings with CPHD due to novel compound heterozygous variants in POU1F1.

Case 1

An 8-year-and-8-month male was presented with short stature to our outpatient clinic. He was born as the first child of healthy nonconsanguineous parents and delivered at term by normal vaginal delivery after uneventful pregnancy. His birth weight was 3360 gr (0.4 standard deviation score (SDS)), birth length was 48 cm (-0.8 SDS). There was no significant abnormality in first months, however failure to thrive showed up at firstly in ninth month. On physical examination, body weight was 24.7 kg (-0.7 SDS), height was 114 cm (-2.9 SDS). Midparental height was 175.5 cm (-0.19 SDS). He had depressed nasal bridge and frontal bossing. Puberty was compatible with Tanner stage 1 and testicles were palpable in the scrotum. He had no goiter. Other systemic physical examination features were unremarkable. Initial laboratory investigations revealed normal blood count, electrolytes and liver-kidney functions. Coeliac tests were all negative. Hormonal evaluation revealed that TSH level was 1,67 mIU/ml (N:0,7-5,97), free T4 was 0,88 ng/dl (N:0.96-1,77), insulin like growth factor- 1 (IGF-1) was 30 ng/ml (-2.6 SDS), IGF-1 binding protein-3 (IGFBP-3) was 1075 mcg/ml (-2.7 SDS), cortisol was 23.5 mcg/dL (N: 6-18.4) and prolactin was 10 mcg/L (N, 5-10). Bone age was found to be delayed; compatible with 7 years according to The Greulich and Pyle atlas. With these findings, a diagnosis of central hypothyroidism was considered and oral L-thyroxine replacement was started. Growth hormone stimulation tests with L-dopa and clonidine revealed a complete lack of growth hormone elevation. Peak growth hormone level was 0.44 ng/mL (N>10).

Case 2

An 8.5 months old female, the sister of the case-1, was presented with failure to thrive to our clinic. She was born as the second child of healthy nonconsanguineous parents and delivered at term by normal vaginal delivery after uneventful pregnancy. She had no history of hypoglycemia or jaundice. Her birth weight was 2980 gr (-0.2 standard deviation score (SDS)), birth length was 48 cm (-0.6 SDS). On physical examination, body weight was 6.1 kg (-3.8 SDS), height was 63 cm (-4.6 SDS). Target height was 162.5 cm (-0.19 SDS). She had depressed nasal bridge and frontal bossing. Tanner stage was compatible with prepubertal and she had no goiter. Other systemic physical examination features were unremarkable. Initial laboratory investigations revealed normal blood count, electrolytes and liver-kidney functions. Coeliac tests were all negative. Hormonal evaluation revealed that TSH level was 0.2 mIU/ml (N:0,7-5,97), free T4 was 0.8 ng/dl (N:0.96-1,77), insulin like growth factor- 1 (IGF-1) was 3 ng/ml (-2,6 SDS), IGF-1 binding protein-3 (IGFBP-3) was 761 mcg/ml (-0,8 SDS), cortisol was 22.3 mcg/dL (N, 6-18.4) and prolactin was 9 mcg/L (N, 5-10). Bone age was compatible with 1 years according to The Greulich and Pyle atlas. With these findings, a diagnosis of central hypothyroidism was considered and oral L-thyroxine replacement was started. Growth hormone stimulation tests with glucagon revealed a complete lack of growth hormone elevation. Peak growth hormone level was 0.23 ng/mL (N>10).

Based on these findings, congenital CPHD involving GH and TSH was diagnosed and growth hormone supplementation (0.35 mcg/kg/d) has been started to the patients after diagnosis. Size and morphology of the pituitary were normal on neuroimaging.

The patients showed catch-up growth after hormone replacement. At the last visit of the patients who have been receiving growth hormone replacement for 12 months; height was 127.5 cm (-1.98 SDS) and 82 cm (- 2.4 SDS) in Case 1 and 2, respectively. Besides this, growth velocity of the Case 1 and 2 was 13.5, 19 cm/year, respectively.

Regarding to the diagnosis of CPHD, genetic analysis performed and Whole exome sequencing (WES) revealed a compound heterozygous in POU1F1 (NM_000306.4) gene; c.688G>A (p.Glu230Lys) and c.438A>T(p.Leu146Phe).

c.688G>A (p.Glu230Lys) variant has been reported as pathogenic according to ACMG criterias with extremely low frequency in gnom AD population databases. c.438A>T (p.Leu146Phe) variant was interpreted as "Uncertain Significance" according to ACMG criterias. Moreover, this variant has not been identified in HGMD (http://www.hgmd.cf.ac.uk) and the Exome Aggregation Consortium (ExAC). The parents were shown to be carriers for the variants. Mother was carrier for the c.688G>A heterozygous variant, while father was carrier for the c.438A>T heterozygous variant. Written informed consents were provided from the parents.

In this study, compound heterozygous variants of the POU1F1 gene were presented from two siblings of CPHD. POU1F1 gene is localized at 3p11.2 and contains six exons [6]. Most of the POU1F1 variants reported in the literature are located in exons 4 and 6, and most of these are missense [2,4,9] . POU1F1 can be inherited autosomal dominant or autosomal recessively.

We identified two different heterozygous variants in POU1F1 gene; c .688G>A (p.Glu230Lys) variant has been reported before [4], c.438A>T (p.Leu146Phe) variant has not been reported in HGMD or public databases.

Turton [4] identified causative POU1F1 mutations in 10 of 129 patients with CPHD or isolated GHD (7.8%). The estimated frequency of POU1F1 mutations in CPHD is 4% in previous data [8]. The frequency of POU1F1 mutations in CPHD patients reported 7.3% in a multi-center study from our country [3].

In patients with POU1F1 mutations; the onset time of the hormone deficiency varies between birth and 18 years, in the literature [2]. Age of diagnosis for CPHD is generally earlier in POU1F1 mutations rather than the other causative mutations, eg. PROP1, HESX1 [3].

In previous studies, the symptoms of patients with POU1F1 mutations are variable. The patients were presented with facial defects such as frontal bossing, prominent forehead, depressed nasal bridge, maxillar hypoplasia, cleft palate, prominent philtrum [2,10,11]. Severe hypoglycemia was reported in a few cases with POU1F1 mutations [2,11].

Complete deficiencies of GH and TSH with/without hypoprolactinemia has been reported in cases with POU1F1 mutations [2,4]. Gonadotrophins and pituitary-adrenal axis were preserved in all cases reported. GHD is usually occurs in early childhood. Central hypothyroidism noted tends to appear later in childhood or adolescence in previous reports but our case 2 has been diagnosed in early childhood [3,4].

Although delayed puberty is a more common feature than central precious puberty in CPHD, CPP was described in two cases with POU1F1 mutations. The mechanism is still unclear; it is most likely due to complex interactions between POU1F1 and GATA2 [12].

Presence of anterior pituitary hypoplasia has been reported in a majority of the cases with POU1F1 mutations [4,13]. However, it has been reported that normal size and morphology of the pituitary may also be observed in MRI, as in our cases [2,8].

In conclusion, we reported two siblings with a compound heterozygous in POU1F1, one of them is novel. Early diagnosis and intervention is important in pituitary hormone deficiencies. It should be kept in mind that onset of hormone deficiencies can vary in POU1F1 mutations.

No funding

Conflict of Interest Statement

The authors have no conflicts of interest to declare.

Ethical Information

Ethical approval was not required for this report in accordance with local guidelines. The study was conducted in accordance with the Principles of Declaration of Helsinki.

Written informed consent was obtained from the patients and their parents for the publication of this case report.

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