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Clinical characteristics and molecular analysis of PIT1, PROP1,LHX3, and HESX1 in combined pituitary hormone deficiency patients with abnormal pituitary MR imaging.

BACKGROUND/AIMS: Many genes encoding pituitary transcription factors involved in the formation of the pituitary gland are identified. Different mutations in these genes have been reported in patients with familial combined pituitary hormone deficiency (CPHD). This study was undertaken to analyze PIT1, PROP1, LHX3, and HESX1 in 12 CPHD patients with abnormal pituitary magnetic resonance imaging (MRI). Since embryonic development of the pituitary requires the coordinated expression of specific transcription factors, we postulated the presence of mutations in PIT1, PROP1, LHX3, and HESX1 genes. METHODS: Anterior pituitary function was evaluated. Each gene was PCR amplified exon by exon, and subsequently sequenced. RESULTS: In all cases, MRI examination showed abnormal pituitary gland development featuring ectopic neurohypophysis, hypoplastic anterior lobe, empty sella, and septo-optic dysplasia. Endocrinologically, all patients revealed multiple pituitary hormone deficiency including growth hormone, thyroid stimulating hormone, luteinizing hormone, follicular stimulating hormone and adrenocorticotropin. They were all sporadic cases without a positive family history. None of disease-causing specific mutations were identified in PIT1, PROP1, LHX3, and HESX1 genes of 12 sporadic CPHD patients with abnormal pituitary imaging. However, 2 novel polymorphisms were found in PROP1 gene: IVS1+3 A-->G and 27 T-->C (Ala9Ala) in exon 1. Their allele frequencies in patients and normal controls were not statistically different. Overall, allele frequencies of these polymorphisms were as follows: for the IVS1+3 A-->G polymorphism, the allele frequency of A was 54%, and 46% for G, with 58% of an A/G heterozygosity. For the 27 T-->C (Ala9Ala) polymorphism, the allele frequency of T was 46%, and 54% for G, with 42% of a T/C heterozygosity. CONCLUSIONS: Mutations of PIT1, PROP1, LHX3, and HESX1 genes are very rare in sporadic CPHD patients with abnormal pituitary MRI.

Adolescent↗

Mutations in PROP1 cause familial combined pituitary hormone deficiency.

Combined pituitary hormone deficiency (CPHD) in man denotes impaired production of growth hormone (GH) and one or more of the other five anterior pituitary hormones. Mutations of the pituitary transcription factor gene POU1F1 (the human homologue of mouse Pit1) are responsible for deficiencies of GH, prolactin and thyroid stimulating hormone (TSH) in Snell and Jackson dwarf mice and in man, while the production of adrenocorticotrophic hormone (ACTH), luteinizing hormone (LH) and follicle stimulating hormone (FSH) is preserved. The Ames dwarf (df) mouse displays a similar phenotype, and appears to be epistatic to Snell and Jackson dwarfism. We have recently positionally cloned the putative Ames dwarf gene Prop1, which encodes a paired-like homeodomain protein that is expressed specifically in embryonic pituitary and is necessary for Pit1 expression. In this report, we have identified four CPHD families with homozygosity or compound heterozygosity for inactivating mutations of PROP1. These mutations in the human PROP1 gene result in a gene product with reduced DNA-binding and transcriptional activation ability in comparison to the product of the murine df mutation. In contrast to individuals with POU1F1 mutations, those with PROP1 mutations cannot produce LH and FSH at a sufficient level and do not enter puberty spontaneously. Our results identify a major cause of CPHD in humans and suggest a direct or indirect role for PROP1 in the ontogenesis of pituitary gonadotropes, as well as somatotropes, lactotropes and caudomedial thyrotropes.

Adolescent↗

[Congenital multiple anterior pituitary hormone deficiencies. An approach of pituitary ontogenesis].

A number of transcription factors evidenced in the pituitary may play a part in the development of this gland, namely Pit-1, Prop-1, P-Lim, Ptx1, Rpx, Dax-1, SF-1. Several of these factors are involved in animal models of hypopituitarism, while up to now only Pit-1 gene alterations have been shown to be responsible for hypopituitarism in man. These factors are briefly presented, and current data on genetically determined uni- or multi-hormonal pituitary deficiencies are reviewed. In particular, data on combined somatotroph, lactotroph and thyrotroph deficiencies due to Pit-1 gene alterations are detailed. Analysis of phenotype-genotype relationships in this syndrome and in other pathological models of multiple pituitary hormone deficiencies will provide useful information on the complex sequence of events that contribute to the development of the pituitary gland and to differentiation and regulation of the different pituitary cell lines.

Animals↗

Mutations in LHX3 result in a new syndrome revealed by combined pituitary hormone deficiency.

Combined pituitary hormone deficiency (CPHD) has been linked with rare abnormalities in genes encoding transcription factors necessary for pituitary development. We have isolated LHX3, a gene involved in a new syndrome, using a candidate-gene approach developed on the basis of documented pituitary abnormalities of a recessive lethal mutation in mice generated by targeted disruption of Lhx3 (ref. 2). LHX3, encoding a member of the LIM class of homeodomain proteins, consists of at least six exons located at 9q34. We identified a homozygous LHX3 defect in patients of two unrelated consanguineous families displaying a complete deficit in all but one (adrenocorticotropin) anterior pituitary hormone and a rigid cervical spine leading to limited head rotation. Two of these patients also displayed a severe pituitary hypoplasia, whereas one patient presented secondarily with an enlarged anterior pituitary. These LHX3 mutations consist of a missense mutation (Y116C) in the LIM2 domain at a phylogenetically conserved residue and an intragenic deletion predicting a severely truncated protein lacking the entire homeodomain. These data are consistent with function of LHX3 in the proper development of all anterior pituitary cell types, except corticotropes, and extrapituitary structures.

Abnormalities, Multiple↗

The interaction of growth hormone releasing hormone with other hypothalamic hormones on the release of anterior pituitary hormones.

To determine whether the 29 amino-acid fragment of growth hormone releasing hormone (GHRH) can be combined with other hypothalamic releasing hormones in a single test of anterior pituitary reserve, the responses of anterior pituitary hormones to combinations of an i.v. bolus of GHRH(1-29)NH2 or saline with an i.v. bolus of either LH releasing hormone (LHRH) plus TRH, ovine CRH(oCRH) or saline were studied. Each infusion of GHRH(1-29)NH2 resulted in a rapid increment of the plasma GH value. Infusion of GHRH(1-29)NH2 also caused a small and transient rise in plasma PRL, but no change in the integrated PRL response. The combination of GHRH(1-29)NH2 with LHRH plus TRH caused a larger increment of peak and integrated plasma TSH levels than LHRH plus TRH alone. GHRH(1-29)NH2 did not affect the release of other anterior pituitary hormones after infusion with oCRH or LHRH plus TRH. Because of the finding of potentiation of the TSH-releasing activity of LHRH plus TRH by GHRH(1-29)NH2, the study was extended to the investigation of TSH release after infusion of TRH in combination with either GHRH(1-29)NH2 or GHRH(1-40). In this study the combination of TRH with both GHRH preparations also caused a larger increment of the peak and integrated plasma TSH levels than TRH alone. It is concluded that GHRH(1-29)NH2 possesses moderate PRL-releasing activity apart from GH-releasing activity. In addition, GHRH potentiates the TSH-releasing activity of TRH.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Pituitary hormones and amnesia.

Pituitary hormones profoundly influence behavior through direct actions on the brain. One of these behavioral effects is the attenuation of experimental amnesia. Traditionally, amnesia is considered as a "loss of memory." Memory comprises at least 2 stages: input (memory consolidation) and output (memory retrieval). Theoretically, disturbance of either aspect of memory may be the cause of amnesia. Also, it is possible that amnesia is based on a factor or factors not related to memory. Data and theories on amnesia in man were reviewed. Some salient features were mentioned: (1) amnesia can be induced by a variety of agents; (2) amnesia covers periods ranging from seconds to years; (3) amnesia gradients can be established; (4) amnesia is to a large extent reversible. From this survey, it seems possible that amnesia is not a homogeneous phenomenon and that even in one person a disturbance of both memory consolidation and memory retrieval may be produced by one and the same event. Animal studies in general have confirmed these conclusions. We have developed an animal model in order to study the effects of pituitary peptides on amnesia. This model is based on CO2-induced amnesia for a one-trial passive avoidance response in rats. This amnesia could be attenuated by treatment with ACTH-analogs 1 hour before the retrieval test. This anti-amnesic effect of ACTH-analogs was not dependent on the nature of the behavioral response or the amnesic treatment. The vasopressin-analog DGLVP similarly exerted an anti-amnesic effect when injected before the retrieval trial. In contrast to ACTH-analogs, however, it also reduced the amnesia when injected before acquisition. These results suggest that amnesia may comprise a "faulty-consolidation" and a "faulty-retrieval" component, which may be amended by different pituitary hormones. The study of the anti-amnesic activity of peptides therefore not only serves to characterize the nature of the behavioral effect of these peptides but may also prove to be helpful of the unraveling of processes involved in amnesia.

Adrenocorticotropic Hormone↗

Combined pituitary hormone deficiency and pituitary hypoplasia due to a mutation of the Pit-1 gene.

Several mutations of the pituitary-specific transcription factor Pit-1 have been identified. We describe a girl with a mutation of the Pit-1 gene leading to a complete lack of GH, TSH and prolactin and a marked hypoplasia of the anterior pituitary gland. The patient had a homozygous nonsense-mutation at position 172 (CGA to TGA), converting arginine into a stop codon, leading to an early termination of protein translation. During the infancy period the girl had very conspicuous symptoms of hypothyroidism and the diagnosis of thyroid insufficiency preceded the diagnosis of GH-deficiency by 1.5 years. Treatment with thyroxine and GH resulted in excellent catch-up growth.

Body Height↗

[From gene to disease; POU1F1- and PROP1-mutations in pituitary hormone deficiency].

Multiple pituitary hormone deficiency can be caused by mutations in at least three pituitary transcription factors: POU1F1 (formerly called PIT1), PROP1 or HESX1. The role of the various pituitary transcription factors in pituitary ontogeny has been elucidated in part for the mouse. In humans, mutations in POU1F1 result in a total deficiency of growth hormone and prolactin, and a variable deficiency of TSH. Cases of mutations in PROP1 exhibit the same deficiencies, with additional deficiencies of gonadotrophins and a variable deficiency of ACTH. In the Netherlands, cases of multiple pituitary hormone deficiency are not only detected on the basis of the classical signs and symptoms of pituitary deficiency, but also by means of screening on congenital hypothyroidism with an incidence of approximately 1:20,000.

Animals↗

The influence of bromocriptine on serum levels of growth hormone and other pituitary hormones and its metabolic effects in active acromegaly.

The effect of treatment with bromocriptine for 12--18 months on serum GH and metabolic responses was studied in sixteen patients with active acromegaly. Of this group ten patients showing a sustained GH reduction of more than 50% during an 8 h bromocriptine test, proved to be responsive to long-term therapy. In the responding patients GH levels decreased to 38% of the pretreatment level after 12 months of therapy. A dose higher than 10 mg did not produce a significantly greater effect. Prolactin and LH levels decreased in all patients, FSH levels showed a significant rise. Testosterone levels in the male patients increased significantly, indicating that the state of hypogonadism can at least be partially reversed. The GH levels became normal in only one patient. We conclude that the role of bromocriptine in acromagaly is limited and selective pituitary operation and/or irradiation is preferred as definitive treatment in most patients.

Acromegaly↗

Growth hormone deficiency and combined pituitary hormone deficiency: does the genotype matter?

The past 12 years have witnessed an explosion in our understanding of the development of the anterior pituitary gland, and of mechanisms that underlie the diagnosis of growth hormone deficiency (GHD) and combined pituitary hormone deficiency (CPHD). The anterior pituitary is the end-product of a carefully orchestrated pattern of expression of signalling molecules and transcription factors that leads to the development of this complex organ secreting six hormones from five different cell types. Naturally occurring and transgenic murine models have demonstrated a role for many of these molecules in the aetiology of GHD/CPHD. These include the transcription factors HESX1, PROP1, POU1F1, LHX3, LHX4, GLI2 and SOX3. Depending upon the expression patterns of these molecules, the phenotype may consist of isolated hypopituitarism, or more complex disorders such as septo-optic dysplasia (SOD) and holoprosencephaly. The phenotype and the mode of inheritance can be highly variable. Novel mutations within the GH-1 and GHRHR genes have also shed light on the phenotype and pathogenesis of isolated GHD (IGHD). To date, genetic mutations have been identified in a modest proportion of patients with IGHD/CPHD and associated syndromes such as SOD. It is, however, clear that many genes remain to be identified, and characterization of these will further elucidate the pathogenesis of these complex conditions.

DNA-Binding Proteins↗

On the isolation of human pituitary hormones.

Six human pituitary hormones can be obtained from a single batch of human pituitary glands by the procedure described. Starting from an acetone powder of the glands, the hormones are segregated into three fractions; one containing GH and PRL, a second containing the glycoprotein hormones, and the third fraction containing smaller peptides including ACTH and MSH. Clinical grade GH is extracted from the residue at alkaline pH, followed by a series of ammonium sulfate and pH fractionations. Further chromatography on G-100 yields a highly purified GH preparation. FSH is purified by chromatography on carboxymethyl cellulose at pH 5.4 followed by gel filtration on G-100 and fractionation on sulfopropyl Sephadex C-50 at pH 5.4. LH and TSH are separated by DEAE-cellulose chromatography at pH 9.5. The GH and glycoprotein hormones are recovered in a highly purified form and good yields. The GH is obtained in an active form which is easily soluble and well suited for clinical use. A large part of the PRL is also saved during the extraction procedure.

Adrenocorticotropic Hormone↗