A novel missense mutation in the thyroid hormone receptor β gene in a kindred with resistance to thyroid hormone

Direct sequencing of exon 9 of the thyroid hormone receptor (TR) gene in a kindred with resistance to thyroid hormone revealed a substitution of threonine for methionine in codon 313 in one allele resulting from a T to C transition. This is a novel missense mutation that resides in one of the two mutational hot-spot regions of the TR gene suggesting altered triiodothyronine binding to this mutant receptor.     

Anti-Müllerian hormone in three intersex conditions.

Anti-Müllerian hormone (AMH), secreted by embryonic testicular Sertoli cells, inhibits the development of Müllerian ducts in the male. An enzyme-linked immunoassay (ELISA) for AMH was used to investigate three intersex infants. The AMH level was correlated with each patient's degree of Müllerian duct development. Complete inhibition of Müllerian structures correlated with the normal levels of AMH in the infant with testicular feminization. Detectable levels of AMH were found in the hermaphroditic infant; however, these low levels reflected Sertoli cell inadequacy of the ovotestis, which was documented by a right rudimentary Fallopian tube and a normal uterus. In the infant with persistent Müllerian duct syndrome, (PMDS), the normal Müllerian derivatives are compatible with 1) an AMH receptor defect; 2) a biologically and immunologically abnormal AMH molecule, or 3) a functional AMH deletion. The lack of detectable AMH in this infant excluded the AMH receptor abnormality and thus directed authors' search for the specific defect to the AMH gene. Thus, this ELISA for AMH is as valuable a tool to the molecular biologist studying a precise genetic error as it is to the physician making a precise clinical diagnosis.     

Plasma thyroxine-binding proteins and thyroid hormone levels in primate species; is callithricidae thyroid hormone resistant?

Thyroxine(T4)-binding to serum proteins in primates; catarrhini, prosimiae, and platyrrhini were studied by polyacrylamide gel electrophoresis T4 binding analysis. From the electrophoretic analysis, it was shown that thyroxine-binding proteins similar to human thyroxine-binding globulin (TBG) and thyroxine-binding prealbumin (TBPA) were present in catarrhini and prosimiae species, but not in platyrrhini (callithricidae and cebidae). T4-binding analysis also revealed that catarrhini and prosimiae have a high affinity T4-binding protein similar to human TBG. The association constant (Ka) for T4 of the plasma proteins in these species was approximately 2.0 X 10(10) M-1. On the other hand, it was unable to demonstrate a high affinity binding site for T4 in the plasma of platyrrhini species. Both the total and free thyroid hormone concentrations in catarrhini and prosimiae were similar to those in human. Total T4 in cebidae, one of the platyrrhini species, was extremely low. Among 8 animals examined, T4 in 6 was undetectable by radioimmunoassay and the mean T4 of the other two was 2.8 micrograms/dl. However, free thyroid hormone concentrations were similar to those in human. In callithricidae, another platyrrhini species, T4 in plasma was 6.90 +/- 2.11, which is comparable to the level in normal human subjects. However, in this species, high-affinity T4-binding protein was lacking and free thyroid hormone concentrations were extremely high (most were higher than the assay limit). Although the thyroid function of callithricidae remains to be studied, it will be interesting if callithricidae is resistant to thyroid hormone action.     

Does the seasonal increase in estradiol negative feedback prevent luteinizing hormone surges in anestrous ewes by suppressing hypothalamic gonadotropin-releasing hormone pulse frequency?

To test the hypothesis that the anestrous increase in estradiol negative feedback prevents estrous cycles by suppressing hypothalamic gonadotropin-releasing hormone (GnRH) pulse frequency, a variety of regimens of increasing GnRH pulse frequency were administered to anestrous ewes for 3 days. A luteinizing hormone (LH) surge was induced in 45 of 46 ewes regardless of amplitude or frequency of GnRH pulses, but only 19 had luteal phases. Estradiol administration induced LH surges in 6 of 6 ewes, only 3 having luteal phases. Anestrous luteal phase progesterone profiles were similar in incidence, time course, and amplitude to those of the first luteal phases of the breeding season, which in turn had lower progesterone maxima than late breeding season luteal phases. In the remaining ewes, progesterone increased briefly or not at all, the increases being similar to the transient rises in progesterone occurring in most ewes at the onset of the breeding season. These results demonstrate that increasing GnRH pulse frequency induces LH surges in anestrus and that the subsequent events are similar to those at the beginning of the breeding season. Finally, they support the hypothesis that the negative feedback action of estradiol prevents cycles in anestrus by suppressing the frequency of the hypothalamic pulse generator.     

Is there growth hormone deficiency in prader-willi Syndrome? Six arguments to support the presence of hypothalamic growth hormone deficiency in Prader-Willi syndrome

Prader-Labhart-Willi syndrome (PWS) is the most frequent form of syndromal obesity. Its main features are associated with hypothalamic dysfunction, which has not yet been comprehensively described. The aim of this review is to present arguments to define the presence of genuine growth hormone (GH) deficiency (GHD) in these patients. Decreasing growth velocity despite the onset of obesity, reduced lean body mass in the presence of adiposity, small hands and feet, relatively low insulin-like growth factor-I and low insulin levels, as well as the dramatic effect of GH treatment on growth, support the presence of hypothalamic GHD in PWS. Even though it might be difficult to ultimately prove GHD in PWS because of the obesity-induced counterregulation, the hormonal situation differs from that in simple obesity. The effects of long-term therapies with GH on body composition in these patients are summarized. GH therapy dramatically changes the phenotype of PWS in childhood: height and weight become normal and there is a sustained impact on the net loss of body fat. We conclude that GHD may account for several features of PWS.     

A role for G proteins in plant hormone signalling?

The G protein signalling pathway is one of the most highly conserved mechanisms that enables cells to sense and respond to changes in their environment. Essential components of this are cell surface G protein-coupled receptors (GPCRs) that perceive extracellular ligands, and heterotrimeric G proteins (G proteins) that transduce information from activated GPCRs to down-stream effectors such as enzymes or ion channels. It is now clear from a range of biochemical and molecular studies that some potential G protein signalling components exist in plants. The best examples of these are the seven transmembrane receptor homologue GCR1 and the G_α (GPA1) and G_β (Gβ1) subunit homologues of heterotrimeric G proteins. G protein agonists and antagonists are known to influence a variety of signalling events in plants and have been used to implicate G proteins in a range of signalling pathways that include the plant hormones gibberellin and auxin. Furthermore, antisense suppression of GCR1 expression in Arabidopsis leads to a phenotype that supports a role for this receptor in cytokinin signalling. This review considers the current evidence for and against functional G protein signalling pathways in higher plants and questions whether or not these might be involved in the action of certain plant hormones.     

The critical period for thyroid hormone responsiveness through thyroid hormone receptor isoform α in the postnatal small intestine

During second and third weeks after birth in rats, serum thyroid hormone level is elevated. In this study, we investigated the jejunal expression of thyroid hormone receptor (TR) α in developing rats. The TRα-1 mRNA level and TRα-1/TRα-2 mRNA ratio increased two-fold from 5 to 13 days after birth. This high level of TRα-1 mRNA was maintained until 20 days and then decreased to the basal level by the end of weaning period at 27 days; however, the level of TRα-2 mRNA remained unchanged throughout the developmental period. The increase in the TRα-1/TRα-2 mRNA ratio from 5 to 13 days was accompanied by an initial rise in the levels of mRNA for hexose transporters in the jejunum. Administration of T₃ during the suckling period (8–13 days) caused a 50% increase in the TRα-1/TRα-2 mRNA ratio, while administration of T₃ on days 12–17 and days 16–21, but not on days 22–27, caused a two to four-fold increase in the levels of mRNA for hexose transporters. These results suggest that a transient variation in the TRα-1/TRα-2 expression ratio is closely related to the critical period of thyroid hormone responsiveness for hexose transporters expression in the developing rat jejunum.     

Two different 5′ splice site mutations in the growth hormone gene causing autosomal dominant growth hormone deficiency

Four distinct types of isolated growth hormone deficiency (IGHD) have been described to date. Of these IGHD type II has been defined as having a dominant mode of inheritance. We performed a molecular genetic analysis of two patients clinically characterized as IGHD type II. One of the patients and her father shared a heterozygous G–A transition in the first 5′ donor splice site of intron III. The second father and daughter studied also showed a heterozygous G–A transition in the fifth base from the 5′ donor splice site in the same intron. Both mutations altered the correct splicing of the growth hormone pre-mRNA when the corresponding genes were expressed in COS-7 cells. We propose that both inherited mutations are responsible for IGHD type II in these patients. Received: 7 April 1997 / Accepted: 13 June 1997     

Discordances between follicle stimulating hormone (FSH) and anti-Müllerian hormone (AMH) in female infertility

Background

Follicle stimulating hormone (FSH) and anti-Müllerian hormone (AMH) represent the two most frequently utilized laboratory tests in determining ovarian reserve (OR). This study determined the clinical significance of their concordance and discordance in female infertility patients.

Methods

We investigated 366 consecutive infertility patients (350 reached IVF), excluding women with polycystic ovarian syndrome (PCOS). They were considered to have normal FSH and AMH if values fell within age-specific (as-) 95% confidence intervals (CI), and to suffer from diminished ovarian reserve (DOR) if FSH exceeded and/or AMH fell below those. The two hormones, thus, could be concordant (Group I), both normal (IA) or abnormal (IB), show normal AMH/abnormal FSH (Group II) or normal FSH/abnormal AMH (Group III). Oocyte yields, stratified for age categories, were then studied in each group as reflection of OR.

Results

Oocyte yields significantly decreased from groups IA to II to III and IB. Predictive values of as-FSH/AMH patterns changed, however, at different ages. Except at very young and very old ages, normal as-AMH better predicted higher oocytes yields than normal as-FSH, though above age 42 years normal as-FSH predicts good oocyte yields even with abnormally low AMH. Under age 42 discrepancies between as- FSH and as-AMH remain similarly predictive of oocyte yields at all ages.

Discussion

Concordances and discordances between as-FSH and as-AMH improve OR assessments and predictability of oocyte yields in IVF.

     

Identification of thyroid hormone response elements in?vivo using mice expressing a tagged thyroid hormone receptor α1

TRα1 (thyroid hormone receptor α1) is well recognized for its importance in brain development. However, due to the difficulties in predicting TREs (thyroid hormone response elements) in silico and the lack of suitable antibodies against TRα1 for ChIP (chromatin immunoprecipitation), only a few direct TRα1 target genes have been identified in the brain. Here we demonstrate that mice expressing a TRα1–GFP (green fluorescent protein) fusion protein from the endogenous TRα locus provide a valuable animal model to identify TRα1 target genes. To this end, we analysed DNA–TRα1 interactions in vivo using ChIP with an anti-GFP antibody. We validated our system using established TREs from neurogranin and hairless, and by verifying additional TREs from known TRα1 target genes in brain and heart. Moreover, our model system enabled the identification of novel TRα1 target genes such as RNF166 (ring finger protein 166). Our results demonstrate that transgenic mice expressing a tagged nuclear receptor constitute a feasible approach to study receptor–DNA interactions in vivo, circumventing the need for specific antibodies. Models like the TRα1–GFP mice may thus pave the way for genome-wide mapping of nuclear receptor-binding sites, and advance the identification of novel target genes in vivo.     

Growth hormone - hormone replacement for the somatopause?

Twenty-four-hour growth hormone (GH) secretion reaches a peak at around puberty and by the age of 21 has begun to decrease. Thereafter the fall in GH secretion is progressive such that by the age of 60 most adults have total 24-hour secretion rates indistinguishable from those of hypopituitary patients with organic lesions in the pituitary gland. Patterns of GH secretion are similar to those in younger people but GH pulses are markedly reduced in amplitude. Sleep and exercise remain the major stimuli for GH secretion. The fall in GH secretion seen with ageing coincides with changes in body composition and lipid metabolism that are similar to those seen in adults with GH deficiency. In elderly subjects, although GH secretion is markedly reduced, remaining GH secretion correlates closely with body composition (particularly with lean body mass and inversely with central abdominal fat). Pioneering studies carried out by Rudman showed that GH administration to elderly subjects with low insulin-like growth factor-I levels resulted in reversal of many of the changes associated with GH deficiency, namely an increase in lean body mass and bone mineral density and a reduction in body fat and plasma cholesterol. These changes were remarkably similar to those shown a year earlier in adults with GH deficiency given GH replacement. Subsequent studies of GH replacement in elderly adults have confirmed Rudman's initial observations but have been dominated by side effects which have led to a high number of dropouts. It is now clear that the elderly are very sensitive to GH and the doses used need to be very low, increased very slowly and tailored to the individual needs of each patient. Using this more cautious approach, recent studies have been very positive. A series of papers from Blackman's group, presented at the US endocrine meeting in San Diego in 1999, investigated the effects of GH with or without testosterone supplements (in men) and oestrogen supplements (in women). Their results showed positive effects of GH on lean body mass, central fat, low-density lipoprotein cholesterol and aerobic capacity. In many instances there was a positive interaction between GH and hormone replacement with testosterone and oestrogen, but it appeared that GH showed the most potent anabolic effects. Clearly more studies are needed before GH replacement for the elderly becomes established. Safety issues will require close scrutiny, but the data available so far are sufficiently positive to undertake large multicentre, placebo-controlled trials, particularly looking at endpoints associated with prevention of frailty and loss of independence.     

Gonadotropin-releasing hormone II (GnRH II) mediates the anorexigenic actions of α-melanocyte-stimulating hormone (α-MSH) and corticotropin-releasing hormone (CRH) in goldfish

Intracerebroventricular (ICV) administration of gonadotropin-releasing hormone II (GnRH II), which plays a crucial role in the regulation of reproduction in vertebrates, markedly reduces food intake in goldfish. However, the neurochemical pathways involved in the anorexigenic action of GnRH II and its interaction with other neuropeptides have not yet been identified. Alpha-melanocyte-stimulating hormone (α-MSH), corticotropin-releasing hormone (CRH) and CRH-related peptides play a major role in feeding control as potent anorexigenic neuropeptides in goldfish. However, our previous study has indicated that the GnRH II-induced anorexigenic action is not blocked by treatment with melanocortin 4 receptor (MC4R) and CRH receptor antagonists. Therefore, in the present study, we further examined whether the anorexigenic effects of α-MSH and CRH in goldfish could be mediated through the GnRH receptor neuronal pathway. ICV injection of the MC4R agonist, melanotan II (80 pmol/g body weight; BW), significantly reduced food intake, and its anorexigenic effect was suppressed by ICV pre-administration of the GnRH type I receptor antagonist, antide (100 pmol/g BW). The CRH-induced (50 pmol/g BW) anorexigenic action was also blocked by treatment with antide. ICV injection of CRH (50 pmol/g BW) induced a significant increase of the GnRH II mRNA level in the hypothalamus, while ICV injection of melanotan II (80 pmol/g BW) had no effect on the level of GnRH II mRNA. These results indicate that, in goldfish, the anorexigenic actions of α-MSH and CRH are mediated through the GnRH type I receptor-signaling pathway, and that the GnRH II system regulates feeding behavior.     

Polygenic expression of gonadotropin-releasing hormone (GnRH) in human?

A non-mammalian lamprey-like gonadotropin-releasing hormone (lGnRH) has been detected in human hypothalami using a combination of immunocytochemistry, high performance liquid chromatography and radioimmunoassay. The hypothalamic distribution of immunopositive lGnRH neurons is similar to that observed for those containing the mammalian gonadotropin-releasing hormone (mGnRH), indicating a possible role for this newly identified peptide in the regulation of pituitary function. Our data suggest the existence of a separate gene for lamprey-like GnRH in humans. Confirmation of the exact nature and role of this newly detected form of GnRH will require future isolation and sequence analysis. The possibility that polygenic expression of a given peptide may be a common phenomenon even in higher mammals is discussed.     

Alteration in the normal pattern of serum testosterone and 5α-androstane-3α,17β-diol in the immature male rat following chronic treatment with luteinizing hormone releasing hormone or luteinizing hormone

A major component of sexual maturation in the male rat is a progressive decline in serum concentrations of 5α-androstane-3α,17β-diol (3α-diol) and a concomitant increase in testicular testosterone biosynthesis and secretion. Chronic administration of synthetic luteinizing hormone releasing hormone (LHRH) or luteinizing hormone (LH)/human chorionic gonadotropin (hCG) to immature male rats has been shown to result in a delay in sexual maturation as evidenced by decreased sex accessory gland weights and altered testicular testosterone production. We have examined the postulate that such treatments may either reverse or retard the normal developmental pattern of serum testosterone and 3α-diol concentrations. Chronic $\text{in vivo}$ treatment of 28 day old immature male rats for 2 weeks with daily injections of either 0.5 μg of LHRH, 1.0 μg of LHRH, or 30 μg of LH was found to result in significant reductions in weights of the seminal vesicles and ventral prostate glands and diminutions in serum testosterone concentrations. Serum content of 3α-diol was either unchanged or slightly elevated in the LHRH treated animals and increased significantly in the LH treated animals. These data suggest that either a reversal of or retardation in the normal developmental pattern of serum testosterone and 3α-diol content has been achieved in the immature male rat by chronic LHRH or LH treatment.     

Immunohistochemical localization of γ-melanocyte-stimulating hormone in the rat pituitary gland

A third melatropin fragment named γ-MSH has been described in the N-terminal portion of the common precursor of bovine ACTH and β-LPH by Nakanishi et al. (Nakanishi, S., Inoue, A., Kita, K., Nakamura, M., Chang, A.C.Y., Cohen, S.N. and Numa, S., Nature, 278 (1979) 423–427). In order to determine if immunoreactive γ-MSH was present in the rat pituitary gland and to accurately localize this peptide, an immunocytochemical localization of γ-MSH was conducted at both light and electron microscopic levels. Specific immunostaining was detected in stellate cells scattered throughout the pars distalis and in all the cells of the pars intermedia. At the ultrastructural level, immunoreactive γ-MSH was only observed in the lipocorticotrophs. Using serial ultrathin sections, it was shown that the secretory granules which contain ACTH were also labeled for γ-MSH. These results suggest that fragment(s) of the common precursor of ACTH and β-LPH and/or the whole common precursor is released with peptides of known biological activity.     

Ghrelin in plants: what is the function of an appetite hormone in plants?

In the present work, we provide compelling evidence for the expression of a ghrelin-like peptide hormone that has only been associated with animals, in various plant tissues. Ghrelin, the appetite stimulating hormone, has been identified from a number of different species including humans, rat, pig, mouse, gerbil, eel, goldfish, bullfrog and chicken. The study here was conducted using an immunohistochemistry assay to screen whether plants have any ghrelin immunoreactivity. In this respect, Prunus x domestica L. and Marus alba were examined. Immunohistochemistry results showed that there is a strong human ghrelin immunoreactivity substance in the parenchyma cells of these plants. This was entirely unexpected since this hormone was considered to be present solely in animals. Thus, this study is the first to report the presence of a peptide with ghrelin-like activity in plants, a finding that has only been observed in the animal kingdom. RIA analysis confirmed that these plants contain significant amounts of this substance. Furthermore, reverse-phase HPLC analyses of plant extracts showed an elution characteristic of the peptide identical to that of human ghrelin. In general, fruit from both plants had higher levels of the peptide than the vegetative parts.     

Localization of luteinizing hormone β-mRNA by in situ hybridization in the sheep pars tuberalis

Summary The localization of luteinizing hormone beta (LH)-mRNA was studied by in situ hybridization in the pars tuberalis of sheep using a homologous sheep double-stranded ³²P-or ³⁵S-cDNA. The labelled cDNA probe detected one mRNA sequence in the pars tuberalis by Northern blot analysis; this sequence was similar to that detected in the pituitary. In situ, the labelling of LH-mRNA in the horizontal and sagittal tissue sections was found throughout the pars tuberalis. This labelling was prevented by adding an excess of cold probe or treating the sections by ribonuclease before in situ hybridization. Controls showed a labelling in the pars distalis, but not in the median eminence, hypothalamus, cerebral cortex and liver sections. Double labelling by using a specific LH-antiserum indicated that the labelling of LH-mRNA appeared more intense in LH-containing cells that were found only in the ventral part of the pars tuberalis. These results suggest that the entire pars tuberalis is able to produce the LH subunit, but that the level of translation greatly varies according to the location of the cells.     

Changes in pituitary hormone levels induced by met-enkephalin in man—The role of dopamine

The interaction of dopamine with the effects of the opiate agonist peptide D-Ala²-MePhe⁴-met-enkephalin-O-o1 (DAMME) on anterior pituitary hormone secretion was investigated in normal male subjects. DAMME produced clear elevations in prolactin, growth hormone and thyroid-stimulating hormone, while inhibiting the release of luteinising hormone and cortisol. There was no change in follicle stimulating hormone. The elevations in prolactin and TSH were enhanced by the dopamine antagonist, domperidone, and blocked by an infusion of dopamine. Neither dopamine nor domperidone modulated the changes in growth hormone, luteinising hormone or cortisol. The data are comptible with the association of the release of prolactin and TSH by opiate peptides with decreased hypothalamic dopaminergic activity; changes in the other anterior pituitary hormones seem to involve different mechanisms.