Isolated adrenocorticotropic hormone deficiency presenting as an acute neurologic emergency in a peripubertal girl.

Isolated adrenocorticotropic hormone (ACTH) deficiency (IAD) is extraordinarily rare, and the clinical manifestations of its accompanying adrenal insufficiency are diverse. Early-onset forms of IAD have been linked to mutations in the Tpit transcription factor gene TPIT; however, the genetic basis of juvenile- or late-onset IAD is unknown. Herein, we describe a case of a peripubertal girl with IAD and a normal TPIT gene who presented with an acute neurologic emergency, demonstrating both the variable clinical presentation of IAD and the need for continued investigation into the molecular mechanisms underlying juvenile- and late-onset IAD.

The TPIT gene mutation M86R associated with isolated adrenocorticotropin deficiency interferes with protein: protein interactions.

CONTEXT: Tpit is a T-box transcription factor important for terminal differentiation of pituitary proopiomelanocortin-expressing cells. We previously showed that human and murine mutations in the gene encoding this highly cortico/melanotrope-specific transcription factor cause a neonatal onset form of congenital isolated ACTH deficiency (IAD). We characterized the largest series of neonatal IAD patients caused by TPIT mutations, and this revealed a highly homogeneous clinical presentation. So far, 12 different loss-of-function TPIT mutations have been identified. The methionine 86 arginine (M86R) TPIT mutation was recently identified in compound heterozygosity with the 782delA frame-shift mutation in two siblings with early-onset IAD. OBJECTIVE: We conducted a functional analysis of the missense M86R mutation to assess transcriptional activity, DNA binding activity, and nuclear location, as well as protein-protein interactions. RESULTS: Although the M86 residue is located within the T-box DNA-binding domain, it did not affect monomer DNA-binding activity per se, but it impaired DNA binding with other DNA-bound proteins, including itself (homodimers) and pituitary homeobox 1 (Pitx1). The M86 residue is at the interface between T domains in the T dimers crystal structure, and it appears that the same residue is involved in heterodimer formation with pituitary Pitx1. Furthermore, TPIT M86R is deficient in the recruitment of the coactivator SRC2 that partly mediates the CRH stimulation of proopiomelanocortin transcription. CONCLUSION: Thus, the M86R TPIT mutation is defining an important surface of the T domain for multiple protein interactions and for transcription.

Genetic screening of combined pituitary hormone deficiency: experience in 195 patients.

CONTEXT: Mutations in transcription factors result in combined pituitary hormone deficiency (CPHD). OBJECTIVE: A genetic screening strategy, based on endocrine and neuroradiological phenotype according to published knowledge, was applied to establish the prevalence of gene defects in each category of patients and provide a useful framework for clinicians to determine the genetic etiology and recurrence risks for individuals and families. DESIGN: One hundred ninety-five CPHD patients from the international GENHYPOPIT network were studied, according to their phenotype, for POU1F1, PROP1, LHX3, LHX4, and HESX1. PATIENTS: Patients selected had two pituitary hormone deficiencies or at least one deficiency with intracerebral malformations. RESULTS: Total prevalence of mutations was 13.3 and 52.4% in 20 patients with familial CPHD history. No mutation of HESX1 was observed in 16 patients harboring septooptic dysplasia. A mutation of LHX4 gene, previously reported, was found in one familial case from 39 patients bearing pituitary stalk interruption syndrome. In 109 patients without extrapituitary abnormalities, 20 had PROP1 mutations, including eight patients with a family history of CPHD. Among 20 patients without pituitary stalk interruption syndrome, no LHX3 gene defect was found, even with a neck rotation deficit. One POU1F1 gene defect was found in one patient presenting the rare postpubertal association of thyrotroph (TSH deficiency) and somatotroph (GH deficiency) deficits. CONCLUSIONS: Mutation of PROP1 gene remains the first to be looked for, and POU1F1 mutations should be sought in GH deficiency and TSH deficiency postpubertal population without extrapituitary malformations. Identification of gene defects allows early treatment of any deficit and prevention of their potentially fatal consequences. Genotyping appears highly beneficial at an individual and familial level.

Identification and functional analysis of the novel S179R POU1F1 mutation associated with combined pituitary hormone deficiency.

CONTEXT: The pituitary-specific transcription factor 1 plays a key role in the development and differentiation of three pituitary cell types: somatotrophs, lactotrophs, and thyrotrophs. Several mutations of the human gene (called POU1F1) have been shown to be responsible for a phenotype of combined pituitary hormone deficiency involving GH, prolactin (PRL), and TSH. OBJECTIVE: We have identified a novel homozygous C to G mutation in exon 4 of the POU1F1 gene (S179R) in a patient with this rare phenotype. We analyzed the functional consequences of this S179R mutation associated with a single-amino acid change in the POU-specific domain. METHODS: Consequences of this mutation on transcriptional activities by transfection studies in alphaT3 cells, DNA binding ability by EMSA, structural properties, and nuclear accumulation of POU1F1 were investigated. RESULTS: The transactivation capacity of this mutant was markedly decreased on the GH1, PRL, TSHbeta, and POU1F1 genes. Interestingly, this mutation abolished the functional interaction of POU1F1 on the PRL promoter with the coactivator cAMP response element-binding protein-binding protein but not with the transcription factor LIM homeodomain transcription factor 3. The S179R mutant displayed normal nuclear accumulation but a markedly decreased binding to a DNA response element in keeping with crystallographic data, suggesting that the S179R mutation might interfere with DNA binding. CONCLUSIONS: Together with previous data, our study indicates that both DNA binding and interaction with cofactors like cAMP response element-binding protein-binding protein are critical for POU1F1 function and that functional and structural properties of abnormal POU1F1 proteins are variously influenced by the type of mutations.

An uncommon phenotype with familial central hypogonadism caused by a novel PROP1 gene mutant truncated in the transactivation domain.

CONTEXT: PROP1 gene mutations are usually associated with childhood onset GH and TSH deficiencies, whereas gonadotroph deficiency is diagnosed at pubertal age. OBJECTIVES: We report a novel PROP1 mutation revealed by familial normosmic hypogonadotropic hypogonadism. We performed in vitro transactivation and DNA binding experiments to study functional consequences of this mutation. SETTING: Three brothers were followed in the Department of Endocrinology of a French university hospital. PATIENTS: These patients from a consanguineous kindred were referred for cryptorchidism and/or delayed puberty. RESULTS: Initial investigations revealed hypogonadotropic hypogonadism. One of the patients had psychomotor retardation, intracranial hypertension, and minor renal malformations. The brothers reached normal adult height and developed GH and TSH deficiencies after age 30. A novel homozygous nonsense mutation (W194X) was found in the PROP1 gene, indicating that the protein is truncated in its transactivation domain. Transfection studies confirmed the deleterious effect of this mutation, whose transactivation capacity was only 34.4% of that of the wild-type. Unexpectedly altered DNA-binding properties suggested that the C-terminal end of the factor plays a role in protein-DNA interaction. CONCLUSIONS: PROP1 mutations should be considered among the growing number of genetic causes of initially isolated hypogonadotropic hypogonadism. This report extends the phenotype variability associated with PROP1 mutations.

Congenital isolated adrenocorticotropin deficiency: an underestimated cause of neonatal death, explained by TPIT gene mutations.

Tpit is a T box transcription factor important for terminal differentiation of pituitary proopiomelanocortin-expressing cells. We demonstrated that human and mouse mutations of the TPIT gene cause a neonatal-onset form of congenital isolated ACTH deficiency (IAD). In the absence of glucocorticoid replacement, IAD can lead to neonatal death by acute adrenal insufficiency. This clinical entity was not previously well characterized because of the small number of published cases. Since identification of the first TPIT mutations, we have enlarged our series of neonatal IAD patients to 27 patients from 21 unrelated families. We found TPIT mutations in 17 of 27 patients. We identified 10 different TPIT mutations, with one mutation found in five unrelated families. All patients appeared to be homozygous or compound heterozygous for TPIT mutations, and their unaffected parents are heterozygous carriers, confirming a recessive mode of transmission. We compared the clinical and biological phenotype of the 17 IAD patients carrying a TPIT mutation with the 10 IAD patients with normal TPIT-coding sequences. This series of neonatal IAD patients revealed a highly homogeneous clinical presentation, suggesting that this disease may be an underestimated cause of neonatal death. Identification of TPIT gene mutations as the principal molecular cause of neonatal IAD permits prenatal diagnosis for families at risk for the purpose of early glucocorticoid replacement therapy.

A familial form of congenital hypopituitarism due to a PROP1 mutation in a large kindred: phenotypic and in vitro functional studies.

We report the natural history of a hypopituitarism in a large Tunisian kindred including 29 subjects from the same consanguineous family. The index case was a 9-yr-old girl with severe growth retardation due to complete GH deficiency and partial corticotroph, lactotroph, and thyrotroph deficiencies. Magnetic resonance imaging showed a hyperplastic anterior pituitary. Thirteen of the 28 relatives examined (10 female subjects) had hypopituitarism. In the 14 patients, previously untreated (aged 6-53 yr), height was -5.7 +/- 1.7 sd score, and puberty was spontaneously initiated in only two females. Complete GH deficiency was found in all 12 patients investigated, of whom 11 had thyrotroph and eight of 10 had corticotroph deficiency. A homozygous R73C mutation of PROP1 was present in all 10 patients studied, and a heterozygous mutation was found in six unaffected parents or siblings. In vitro the mutant had 11.5% of the transactivation capacity of the wild type and was unable to bind to a high-affinity DNA sequence. This report showed the deleterious effect of the recessive R73C mutation that affects a hot spot of the PROP1 gene and was associated with severe dwarfism, a lack of spontaneous puberty, and a high incidence of early onset of corticotroph deficiency.

Differential regulation of proopiomelanocortin and pituitary-restricted transcription factor (TPIT), a new marker of normal and adenomatous human corticotrophs.

Since the identification of the pituitary-restricted transcription factor Tpit, a novel T-box factor that is only present in mouse in the two pituitary proopiomelanocortin (POMC)-expressing lineages, no information was available on its pattern of expression in human pituitary. We investigated by immunohistochemistry and in situ hybridization the expression of TPIT in normal human anterior pituitary tissue and in several types of human pituitary adenomas (n = 52). TPIT expression was restricted to the nucleus of normal or adenomatous human corticotroph cells. No specific TPIT immunostaining was detectable in all prolactin (PRL)-, GH-, or gonadotropin-secreting adenomas. In situ hybridization studies demonstrated that TPIT transcripts were coexpressed with POMC mRNA in both secreting and silent corticotroph adenomas, and in normal corticotrophs, whereas TPIT mRNA was not detectable in other types of pituitary adenomas. Unlike POMC, TPIT was not up-regulated by adrenalectomy in rats and did not seem down-regulated in the normal pituitary adjacent to human corticotroph microadenomas. TPIT is the only currently known transcription factor selectively expressed in human normal and adenomatous corticotrophs. In human and experimental models, TPIT and its target gene POMC were thus differentially regulated by glucocorticoids. Moreover, TPIT represents a new marker of POMC-expressing pituitary cells.

Macroprolactinemia revisited: a study on 106 patients.

The predominance of high molecular weight PRL, or macroprolactinemia, has long been known in hyperprolactinemic patients with maintained fertility. Among 1,106 consecutive patients investigated for hyperprolactinemia in our center over a 10-yr period, serum PRL chromatography was performed in 368 cases because of discordant clinical, biological, or neuroradiological findings. We prospectively studied the 106 patients with macroprolactinemia (96 women, 6 men, 4 children) and compared them with the 262 hyperprolactinemic patients with a normal PRL elution pattern. We concluded the following: 1) the incidence of macroprolactinemia in our hyperprolactinemic population was at least 10%; 2) despite preserved fertility with uneventful pregnancies, some of the usual symptoms of hyperprolactinemia were present; 3) mean PRL values were 61 +/- 66 microg/liter (range, 20-663) and exceeded 100 microg/liter in 8.5% of patients; 4) PRL levels usually remained stable over time; 5) on dopaminergic therapy, PRL returned to normal in 21 of 45 treated patients; 6) during follow-up of 7 pregnancies, PRL increased to supraphysiological levels in 5; and 7) pituitary magnetic resonance imaging was normal in 78% of patients or revealed diverse pituitary lesions, including adenomas (n = 5). A diagnostic method for macroprolactinemia should be available to all centers to avoid unnecessary hormonal or radiological investigations and treatments.

The desmopressin test as a predictive factor of outcome after pituitary surgery for Cushing's disease.

OBJECTIVE: Taking advantage of the over-expression of V3 receptors in adenomatous corticotroph cells, we evaluated the response to the vasopressin agonist desmopressin in 22 patients operated on for Cushing's disease, with a mean follow-up of 4.5 years. SUBJECTS AND METHODS: Twenty-two patients (17 women) operated on for Cushing's disease with a follow-up >2 years (median, 48; range, 24-141 months) underwent one desmopressin test (10 microg i.v. bolus) 3-6 months postoperatively. Twelve were in remission (R group), five had immediate failure (IF) after surgery and five had late recurrence (LR). RESULTS: Both ACTH and cortisol peaks after desmopressin were significantly lower in the R group than in the LR group (P=0.003 and P=0.013 respectively). The receiver operator characteristic curve method defined an ACTH peak threshold > or =22 pg/ml or ACTH rise > or =35%; cortisol peak > or =350 nmol/l or cortisol rise > or =14%. None of twelve patients in remission had ACTH or cortisol peaks above these thresholds vs three of five patients from the LR group and five of five in the IF group. DISCUSSION: On the basis of ACTH or cortisol peaks respectively, the desmopressin test was predictive of a later recurrence with a positive predictive value of 100% or 80% respectively, and a negative predictive value of 92%. Sensitivity and specificity were 80% and 100% respectively based on ACTH peak, and 80% and 92% respectively based on cortisol peak. CONCLUSION: In this first long-term study, a marked response of ACTH or cortisol to desmopressin was predictive of a later recurrence with good specificity and sensitivity.

[Tpit mutations reveal a new model of pituitary differentiation and account for isolated ACTH deficiency]. / Mutations du facteur de transcription Tpit et différenciation hypophysaire.

Pituitary hormone-producing cells differentiate sequentially from a common epithelial primordium, Rathke's pouch, under the combinatorial action of a subset of tissue- and cell-restricted transcription factors. Some factors have been implicated in early events of pituitary induction and morphogenesis while other factors like Pit-1 and SF-1 have been associated with differentiation of particular lineages. In POMC-expressing cells, Pitx1, NeuroD1 and Tpit were shown to be important for cell specific transcription of the POMC gene. Since Tpit is exclusively expressed in pituitary POMC-expressing lineages, the corticotrophs and melanotrophs, we investigated the TPIT gene coding sequences in 17 patients presenting with congenital isolated ACTH deficiency (IAD). We demonstrated that human TPIT gene mutations cause a neonatal onset form of IAD (8/11), but not juvenile forms of this deficiency (0/6). In the absence of glucocorticoid replacement, IAD can lead to neonatal death by acute adrenal insufficiency. To assess the importance of Tpit in pituitary differentiation and function, we produced Tpit-null mice. Concordant with the human phenotype, Tpit-null mice have IAD : plasma ACTH is greatly reduced in these mice, their plasma corticosterone is undetectable and the adrenals are hypoplastic. Analysis of the pituitary in Tpit-null mice revealed multiple roles of this factor in cell differentiation. First, Tpit is a positive regulator for POMC cell differentiation. Tpit is also a negative regulator of the pituitary gonadotroph fate. Thus, Tpit operates as a molecular switch to orient differentiation of a common precursor towards either POMC or gonadotroph fate. A binary choice model of pituitary cell differentiation is presented.

Low estriol levels in the maternal triple-marker screen as a predictor of isolated adrenocorticotropic hormone deficiency caused by a new mutation in the TPIT gene.

Isolated adrenocorticotropic hormone (ACTH) deficiency (IAD) is a rare cause of adrenocortical insufficiency, especially in children, and may be an underestimated cause of neonatal death. Early postnatal diagnosis may prevent hypoglycemic seizures, Addisonian crises, and death. There are also occasional reports of prenatal diagnosis of IAD by findings on the maternal triple-marker screen (TMST), a combined serum analyte test that measures levels of alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol for the detection of Down syndrome and open neural-tube defects. An isolated low estriol level is usually correlated with compromised uteroplacental perfusion and frequently associated with fetal death. A low estriol level in the context of normal fetal sonography and growth, after exclusion of placental sulfatase deficiency and Smith-Lemli-Opitz syndrome, should raise the suspicion of deficient fetal steroidogenesis, which leads to decreased production of adrenal dehydroepiandrosterone sulfate. We describe 2 brothers with adrenal insufficiency resulting from IAD. The parents are first cousins whose first son is healthy. During the pregnancy of the second son, who died at the age of 7 weeks as a result of presumed cardiomyopathy, a low estriol level on the TMST was ignored because of a normal fetal ultrasound. In the third pregnancy, a low level was found again, and the mother was referred to our tertiary center. Ultrasonography revealed no abnormalities, and karyotype was normal. Normal levels of steroid sulfatase activity and 7-dehydrocholesterol ruled out X-linked ichthyosis and Smith-Lemli-Opitz syndrome, respectively. Postnatally, basal and stimulated cortisol and ACTH levels were low. Other pituitary functions were normal, suggesting the diagnosis of IAD. The patient was treated with a stress dose of hydrocortisone on day 2 of life, which was tapered to a maintenance dose. At the time of this writing, he was 7 months old, with normal growth and development. Recently, loss-of-function mutations in the human TPIT gene were detected in autosomal recessive IAD. TPIT is a cell-restricted T-box transcription factor that is important for the terminal differentiation of pituitary corticotrophs. Therefore, we performed molecular analysis of the TPIT gene, which revealed a new mutation (IVS4+1G>A) that affects the first nucleotide of the splice site at the 5' end of the fourth intron. This stop codon probably leads to loss of TPIT function by nonsense-mediated mRNA decay, as it does for other TPIT nonsense mutations. We recommend that pregnant women with an isolated low estriol level of unexplained etiology be referred for additional evaluation by a multidisciplinary team that includes a geneticist and pediatric endocrinologist. Prompt ACTH testing in the first postnatal days will allow for early diagnosis. The immediate institution of glucocorticoid therapy, with proper instructions for stress management, can prevent unnecessary neonatal death secondary to an easily treatable disease.

Role of Brg1 and HDAC2 in GR trans-repression of the pituitary POMC gene and misexpression in Cushing disease.

Negative feedback regulation of the proopiomelanocortin (POMC) gene by the glucocorticoid (Gc) receptor (GR) is a critical feature of the hypothalamo-pituitary-adrenal axis, and it is in part exerted by trans-repression between GR and the orphan nuclear receptors related to NGFI-B. We now show that Brg1, the ATPase subunit of the Swi/Snf complex, is essential for this trans-repression and that Brg1 is required in vivo to stabilize interactions between GR and NGFI-B as well as between GR and HDAC2. Whereas Brg1 is constitutively present at the POMC promoter, recruitment of GR and HDAC2 is ligand-dependent and results in histone H4 deacetylation of the POMC locus. In addition, GR-dependent repression inhibits promoter clearance by RNA polymerase II. Thus, corecruitment of repressor and activator at the promoter and chromatin modification jointly contribute to trans-repression initiated by direct interactions between GR and NGFI-B. Loss of Brg1 or HDAC2 should therefore produce Gc resistance, and we show that approximately 50% of Gc-resistant human and dog corticotroph adenomas, which are the hallmark of Cushing disease, are deficient in nuclear expression of either protein. In addition to providing a molecular basis for Gc resistance, these deficiencies may also contribute to the tumorigenic process.

Tpit determines alternate fates during pituitary cell differentiation.

The T-box transcription factor Tpit was identified as a cell-specific factor for expression of the pituitary proopiomelanocortin (POMC) gene. Expression of this factor is exclusively restricted to the pituitary POMC-expressing lineages, the corticotrophs and melanotrophs. We have now determined the role of this factor in pituitary cell differentiation. Tpit is a positive regulator for late POMC cell differentiation and POMC expression, but it is not essential for lineage commitment. The pituitary intermediate lobe normally contains only Tpit-expressing melanotrophs. Inactivation of the Tpit gene results in almost complete loss of POMC-expressing cells in this tissue, which now has a large number of gonadotrophs and a few clusters of Pit-1-independent thyrotrophs. The role of Tpit as a negative regulator of gonadotroph differentiation was confirmed in transgenic gain-of-function experiments. One mechanism to account for the negative role of Tpit in differentiation may be trans-repression between Tpit and the gonadotroph-restricted factor SF1. These data suggest that antagonism between Tpit and SF1 may play a role in establishment of POMC and gonadotroph lineages and that these lineages may arise from common precursors.

Human and mouse TPIT gene mutations cause early onset pituitary ACTH deficiency.

Tpit is a highly cell-restricted transcription factor that is required for expression of the pro-opiomelanocortin (POMC) gene and for terminal differentiation of the pituitary corticotroph lineage. Its exclusive expression in pituitary POMC-expressing cells has suggested that its mutation may cause isolated deficiency of pituitary adrenocorticotropin (ACTH). We now show that Tpit-deficient mice constitute a model of isolated ACTH deficiency (IAD) that is very similar to human IAD patients carrying TPIT gene mutations. Through genetic analysis of a panel of IAD patients, we show that TPIT gene mutations are associated at high frequency with early onset IAD, but not with juvenile forms of this deficiency. We identified seven different TPIT mutations, including nonsense, missense, point deletion, and a genomic deletion. This work defines congenital early onset IAD as a relatively homogeneous clinical entity caused by recessive transmission of loss-of-function mutations in the TPIT gene.