Growth hormone-releasing peptide-2 stimulates GH secretion in GH-deficient patients with mutated GH-releasing hormone receptor

GH-releasing peptides (GHRPs) are synthetic peptides that bind to specific receptors and thereby stimulate the secretion of pituitary GH. In vivo it is uncertain whether these peptides act directly on somatotroph cells or indirectly via release of GHRH from the hypothalamus. In this study we compared the pituitary hormone response to GHRP-2 in 11 individuals with isolated GH deficiency (GHD) due to a homozygous mutation of the GHRH receptor (GHRH-R) gene and in 8 normal unrelated controls. Basal serum GH levels were lower in the GHD group compared with controls [0.11 +/- 0.11 (range, <0.04 to 0.38) vs. 0.59 +/- 0.76 microg/L (range, 0.04-2.12 microg/L); P = 0.052]. After GHRP-2 administration there was a 4.5-fold increase in serum GH relative to baseline values in the GHD group (0.49 +/- 0.41 vs. 0.11 +/- 0.11 microg/L; P = 0.002), which was significantly less than the 79-fold increase in the control group (46.8 +/- 17.6 vs. 0.59 +/- 0.76 microg/L; P = 0.008). Basal and post-GHRP-2 serum levels of ACTH, cortisol, and PRL were similar in both groups. Basal levels of serum TSH were significantly higher in the GHD group than in the control group (3.23 +/- 2.21 vs. 1.37 +/- 0.34 microIU/mL; P = 0.003). TSH levels in both groups did not change after GHRP-2 administration. These results suggest that an intact GHRH signaling system is not an absolute requirement for GHRP-2 action on GH secretion and that GHRP-2 has a GHRH-independent effect on pituitary somatotroph cells.

Study of the multiple endocrine neoplasia type 1, growth hormone-releasing hormone receptor, Gs alpha, and Gi2 alpha genes in isolated familial acromegaly

Familial acromegaly may occur as an isolated pituitary disorder or as a feature of hereditary syndromes, such as multiple endocrine neoplasia type 1 (MEN1) or the Carney complex. Herein, we characterized a newly identified kindred with isolated acromegaly and searched for germline mutation in genes that have been associated with endocrine tumors [i.e. MEN1, Gs alpha (GNAS1), and Gi2 alpha (GNAI2)], as well as the GHRH receptor (GHRH-R) gene. Genomic DNA was used to amplify exons 2-10 of MEN1, followed by dideoxy fingerprinting mutation analysis and direct sequencing. The GHRH-R gene was analyzed via direct sequencing of PCR-amplified fragments representing the coding exons and intron-exon junctions. To exclude mutation at hot spot areas of GNAS1 and GNAI2, exons 8 and 9 of GNAS1 and exons 5 and 6 of GNAI2 were amplified and screened for mutation via denaturing gradient gel electrophoresis. No mutations were detected in any of the four genes. The present data extend prior reports of the absence of mutation in MEN1, GHRH-R, and GNAS1 and describe the first family with isolated acromegaly in which germline mutation in GNAI2 has been searched.

Acheiropodia is caused by a genomic deletion in C7orf2, the human orthologue of the Lmbr1 gene

Acheiropodia is an autosomal recessive developmental disorder presenting with bilateral congenital amputations of the upper and lower extremities and aplasia of the hands and feet. This severely handicapping condition appears to affect only the extremities, with no other systemic manifestations reported. Recently, a locus for acheiropodia was mapped on chromosome 7q36. Herein we report the narrowing of the critical region for the acheiropodia gene and the subsequent identification of a common mutation in C7orf2-the human orthologue of the mouse Lmbr1 gene-that is responsible for the disease. Analysis of five families with acheiropodia, by means of 15 polymorphic markers, narrowed the critical region to 1.3 cM, on the basis of identity by descent, and to <0.5 Mb, on the basis of physical mapping. Analysis of C7orf2, the human orthologue of the mouse Lmbr1 gene, identified a deletion in all five families, thus identifying a common acheiropodia mutation. The deletion was identified at both the genomic-DNA and mRNA level. It leads to the production of a C7orf2 transcript lacking exon 4 and introduces a premature stop codon downstream of exon 3. Given the nature of the acheiropodia phenotype, it appears likely that the Lmbr1 gene plays an important role in limb development.

Familial growth hormone deficiency with mutated GHRH receptor gene: clinical and hormonal findings in homozygous and heterozygous individuals from Itabaianinha

OBJECTIVE

To characterize clinically and hormonally the syndrome of autosomal recessive familial growth hormone deficiency (FGHD) recently identified in Itabaianinha, Sergipe, Brazil, caused by a novel mutation (mt) that inactivates the growth hormone-releasing hormone receptor (GHRH-R) gene.

DESIGN

Clinical and hormonal evaluations were performed in 21 FGHD individuals (mt/mt group) aged 8 to 63 years, 13 heterozygotes for the GHRH-R mutation (wt/mt group) and 5 homozygotes for the wild type (wt) allele (wt/wt group), identified by genotyping of peripheral blood leukocyte DNA.

METHODS

Clinical and hormonal characterization included physical examination and measurement of GH, IGF-I, IGF binding protein-3 (IGFBP-3), cortisol, prolactin, LH, FSH, and free thyroxine (FT4).

RESULTS

Clinical features were consistent with isolated growth hormone deficiency. Height was significantly reduced in the mt/mt group compared with the wt/mt group (mean height standard deviation score (SDS) +/- s.d.: -7.35+/-1.37 vs -1.84+/-1.44 respectively, P<0. 0001), and the wt/wt group (-1.85 +/- 0.81, P=0.0007). The height of the 13 wt/mt subjects did not differ from the 5wt/wt individuals. Serum GH, IGF-I, IGF-I SDS, IGFBP-3 and IGFBP-3 SDS were all significantly lower in the mt/mt group than in the wt/mt and wt/wt groups. Two affected children treated with GH for 1 year showed a normal growth response. Serum IGF-I and IGF-I SDS were lower in wt/mt compared with wt/wt group, but did not reach statistical significance. IGF-I and IGF-I SDS correlated inversely with age in wt/mt group.

CONCLUSIONS

FGHD due to an autosomal recessive GHRH-R gene mutation leads to marked dwarfism, phenotypically and hormonally indistinguishable from other forms of isolated GH deficiency. Heterozygotes for the GHRH-R mutation appear to have a partial defect in the GH/IGF axis, with no apparent height impairment.

Impaired adrenocorticotropin-adrenal axis in combined pituitary hormone deficiency caused by a two-base pair deletion (301-302delAG) in the prophet of Pit-1 gene

The Prophet of Pit-1 gene (PROP1) encodes a paired-like homeodomain protein, which is expressed early in pituitary gland development. When mutated, it is responsible for combined pituitary hormone deficiency (CPHD) in humans, as well as in Ames dwarf mice (df/df). Several independent mutations in the homeodomain of PROP1 have been identified as causative for the human CPHD phenotype, which has been characterized, thus far, as absence or low levels of GH, PRL, TSH, LH, and FSH. Here, we report 10 CPHD cases, 9 of which were born to consanguineous marriages occurring in a large family living in an isolated area in the Southeast of Brazil. All affected patients present complete absence of puberty and low GH, PRL, TSH, LH, and FSH associated with severe hypoplasia of the pituitary gland, as seen by MRI. All 3 exons of the PROP1 genes of these patients were sequenced. The 301-302delAG frameshift mutation was found in both alleles of each affected case. Surprisingly, we observed ACTH/cortisol insufficiency associated with the PROP1 phenotype. The patients' ages varied between 8 and 67 yr, and cortisol response impairment was identified in 5 of 6 of the older patients and in an 11-yr-old patient. Previous studies have not fully characterized patients at advanced ages, leading us to conclude that the phenotype of this PROP1 mutation includes late-onset adrenal insufficiency. We present an extensive clinical analysis of all of these patients. The presence of ACTH/cortisol deficiency in this family bearing the PROP1 301-302delAG mutation indicates the importance of a complete endocrine characterization and of life-long monitoring of PROP1 patients.

Differences in allelic distribution of two polymorphisms in the VHL-associated gene CUL2 in pheochromocytoma patients without somatic CUL2 mutations

Although the two major familial forms of pheochromocytomas, multiple endocrine neoplasia type 2 and von-Hippel-Lindau disease (VHL), have been associated with mutations of the RET and VHL genes, respectively, the molecular pathogenesis of sporadic pheochromocytomas is largely unknown. Recently, a putative tumor suppressor gene has been identified, CUL2, whose product has been shown to interact with the VHL tumor suppressor. To examine whether CUL2 plays a role in pheochromocytoma pathogenesis, we analyzed a series of 26 distinct tumor samples for mutations in the whole coding region of this gene. There were no somatic pathogenic mutations in CUL2, except for 1 sporadic tumor that had a hemizygous gene deletion. We also found 3 novel polymorphisms in the gene. One of these variants, IVS5-6C/T, as well as another previously described one, c.2057G/A, were overrepresented among the pheochromocytoma patients compared to that in a control population (P < 0.005 and P < 0.01, respectively). Although our findings suggest that CUL2 does not play a major role in the pathogenesis of pheochromocytomas, it is still unknown whether epigenetic mechanisms are involved in its inactivation in VHL-associated tumors. Furthermore, the potential role for the overrepresented alleles in the pheochromocytoma group requires further investigation.

Familial dwarfism due to a novel mutation of the growth hormone-releasing hormone receptor gene

Isolated growth hormone (GH) deficiency (IGHD) is a rare cause of short stature. The same mutation of the gene encoding the growth hormone-releasing hormone receptor (GHRHR) has been identified as the basis for IGHD in three families from the Indian subcontinent. The prevalence and heterogeneity of defects in the GHRHR gene are not known. Twenty-two dwarf members of a large, extended kindred containing at least 105 affected members with autosomal recessive short stature underwent extensive endocrine evaluation, which confirmed markedly reduced or undetectable serum concentrations of GH that did not increase in response to different stimuli. DNA sequences of the 13 exons and intron-exon boundaries of the GHRHR gene were determined in an index patient. A novel homozygous 5' splice site mutation (G-->A at position +1) in IVS1 was found. Thirty of the affected subjects tested were homozygous for this mutation, and 64 clinically unaffected patients were either heterozygous for the mutation (n = 41, including 9 obligate carriers) or homozygous for the wild-type sequence (n = 23). We describe a novel mutation in the GHRHR gene as cause of dwarfism in the largest kindred with familial IGHD described to date.

Evaluation of gonadal function in 107 intersex patients by means of serum antimüllerian hormone measurement

Fetal male sexual differentiation is driven by two testicular hormones: testosterone (synthesized by interstitial Leydig cells) and antimüllerian hormone (AMH; produced by Sertoli cells present in the seminiferous tubules). Intersex states result either from gonadal dysgenesis, in which both Leydig and Sertoli cell populations are affected, or from impaired secretion or action of either testosterone or AMH. Until now, only Leydig cell function has been assessed in children with ambiguous genitalia, by means of testosterone assay. To determine whether serum AMH would help in the diagnosis of intersex conditions, we assayed serum AMH levels in 107 patients with ambiguous genitalia of various etiologies. In XY patients, AMH was low when the intersex condition was caused by abnormal testicular determination (including pure and partial gonadal dysgenesis) but was normal or elevated in patients with impaired testosterone secretion, whereas serum testosterone was low in both groups. AMH was also elevated during the first year of life and at puberty in intersex states caused by androgen insensitivity. In 46,XX patients with a normal male phenotype or ambiguous genitalia, in whom the diagnosis of female pseudohermaphroditism had been excluded, serum AMH levels higher than 75 pmol/L were indicative of the presence of testicular tissue and correlated with the mass of functional testicular parenchyma. In conclusion, serum AMH determination is a powerful tool to assess Sertoli cell function in children with intersex states, and it helps to distinguish between defects of male sexual differentiation caused by abnormal testicular determination and those resulting from isolated impairment of testosterone secretion or action.

Calcitonin deficiency in early stages of chronic autoimmune thyroiditis

OBJECTIVES

Although calcitonin (Ct) deficiency has been described in chronic autoimmune thyroiditis (CAT) it is unclear at what stage in the disease it develops. We have analysed the Ct secretory responses of patients in two different evolutionary stages of CAT, namely the goitrous and atrophic phases.

DESIGN

We studied the Ct response to combined calcium (2 mg/kg) and pentagastrin (0.5 microgram/kg) intravenous infusion in 27 patients with CAT and 30 normal adult controls. The cases were divided into two groups. The first comprised eleven women with CAT and goitrous subclinical hypothyroidism (GH), aged 28.6 +/- 10.1 years--at diagnosis they had increased thyroid autoantibody titres and cytological features compatible with stages 1 and 2 of Hashimoto's thyroiditis. The second comprised 16 females with CAT and an atrophic thyroid confirmed by ultrasound scan, aged 38.0 +/- 9.2 years--these patients were severely hypothyroid at diagnosis and were termed AH (atrophic hypothyroidism). Both groups (GH and AH) received replacement doses of thyroxine sufficient to restore euthyroidism for at least six months before the stimulation tests. Control group (C) consisted of 20 healthy women (A), aged 30.0 +/- 9.6 years, and 10 healthy men (B), aged 34.7 +/- 8.0 years. Serum Ct was measured by IRMA. The Ct secretory response was related to thyroid size and cytological data, when available.

RESULTS

Basal Ct concentrations in groups GH (0.08 ng/l, median) and AH (0.07 ng/l, median) were significantly lower than those of female controls (0.58 ng/l, median). Stimulated Ct peak values in groups GH (0.08 ng/l, median) and AH (0.19 ng/l, median) were significantly lower than those of female controls (13.61 ng/l, median). Also, both basal (2.72 ng/l, median) and stimulated Ct levels (35.73 ng/l, median) in male controls were significantly higher than in female controls given already. A positive correlation between the Ct secretory reserve and thyroid dimensions, evaluated by ultrasound scan, was found only in patients with thyroid atrophy (AH; rs = 0.61, P < 0.05).

CONCLUSIONS

We have found low basal and stimulated calcitonin values in patients with chronic autoimmune thyroiditis and thyroid enlargement, which represents an early phase of chronic autoimmune thyroiditis. Our data have also confirmed previous findings of deficient calcitonin secretion in advanced stages of chronic autoimmune thyroiditis in which thyroid atrophy is usually found. These findings may be associated with C-cell destruction following progressive, nonspecific follicular cell damage caused by lymphocytic infiltration and fibrosis of the gland.

A homozygous mutation in the luteinizing hormone receptor causes partial Leydig cell hypoplasia: correlation between receptor activity and phenotype

Leydig cell hypoplasia (LCH) is characterized by a decreased response of the Leydig cells to LH. As a result, patients with this syndrome display aberrant male development ranging from complete pseudohermaphroditism to males with micropenis but with otherwise normal sex characteristics. We have evaluated three brothers with a mild form of LCH. Analysis of their LH receptor (LHR) gene revealed a homozygous missense mutation resulting in a substitution of a lysine residue for a isoleucine residue at position 625 of the receptor. In vitro analysis of this mutant LHR, LHR(I625K), in HEK293 cells indicated that the signaling efficiency was significantly impaired, which explains the partial phenotype. We have compared this mutant LHR to two other mutant LHRs, LHR(A593P) and LHR(S616Y), identified in a complete and partial LCH patient, respectively. Although the ligand-binding affinity for all three mutant receptors was normal, the hormonal response of LHR(A593P) was completely absent and that of LHR(S616Y) and LHR(I625K) was severely impaired. Low cell surface expression explained the reduced response of LHR(S616Y), while for LHR(I625K) this diminished response was due to a combination of low cell surface expression and decreased coupling efficiency. For LHR(A593P), the absence of a reduced response resulted from both poor cell surface expression and a complete deficiency in coupling. Our experiments further show a clear correlation between the severity of the clinical phenotype of patients and overall receptor signal capacity, which is a combination of cell surface expression and coupling efficiency.

Mutation analysis of glial cell line-derived neurotrophic factor (GDNF), a ligand for the RET/GDNF receptor alpha complex, in sporadic phaeochromocytomas

Phaeochromocytomas usually occur sporadically but may also be a feature of three autosomal dominantly inherited cancer syndromes, multiple endocrine neoplasia type 2, von Hippel-Lindau disease (VHL), and, very rarely, type 1 neurofibromatosis. Germ-line missense mutations in the RET proto-oncogene, which encodes a receptor tyrosine kinase, cause multiple endocrine neoplasia type 2. In VHL, germ-line mutations in one of the three exons of the VHL tumor suppressor gene have been found in the majority of families. Whereas somatic mutations in the VHL gene have been common in sporadic renal cell carcinoma, a component cancer of VHL, somatic mutations in the RET and VHL genes together have been found in approximately 10% of sporadic phaeochromocytomas. Hence, other genes must also contribute to the pathogenesis of sporadic phaeochromocytomas. Recent data have suggested that glial cell line-derived neurotrophic factor (GDNF) is a ligand for RET and acts via a heterotetrameric receptor complex that includes GDNF receptor alpha, which provides ligand binding capabilities, and RET, which provides the signaling component. Thus, both GDNF and GDNFR-alpha are plausible candidate genes for involvement in the pathogenesis of phaeochromocytomas. To investigate the role of GDNF in sporadic phaeochromocytomas, we scanned a panel of 22 tumors. Among these samples, only a conservative sequence variant was detected in exon 2 of GDNF. No disease-associated somatic GDNF mutations or gross gene amplification were detected in these tumors, suggesting only a minor role for GDNF in the genesis of phaeochromocytomas.

An inactivating mutation of the luteinizing hormone receptor causes amenorrhea in a 46,XX female

Hypergonadotropic hypogonadism is characterized by decreased gonadal function due to the inability of the gonads to respond to pituitary gonadotropins. Hypergonadotropic hypogonadism in females has many causes, among which are ovarian dysgenesis and abnormalities of the ovarian receptors for the pituitary gonadotropins. We evaluated a woman who presented with amenorrhea due to hypergonadotropic hypogonadism, but who had structurally normal ovaries. She is a sister of two previously identified 46,XY male pseudohermaphrodites with Leydig cell hypoplasia. Injection of hCG did not cause any change in plasma levels of estradiol or progesterone, suggesting complete ovarian resistance to LH. Analysis of the DNA sequence of the LH receptor gene revealed that the patient is homozygous for the same single base change as her two brothers. This mutation causes substitution of an alanine residue by a proline at position 593. In vitro analysis of the mutant LH receptor in cultured human embryonic kidney 293 cells documented that the receptor is unable to stimulate adenylyl cyclase in response to hCG. Plasma levels of estradiol and progesterone were low, whereas LH and FSH levels were increased. On histological analysis of the ovary, follicles were seen at all developmental stages. Nonetheless, primary amenorrhea had been present for 5 yr, and repeated measurements of plasma estradiol and progesterone indicate that ovulation does not occur. These results document the existence of inherited LH resistance as a cause of primary amenorrhea in women. The combined clinical and molecular observations are consistent with previous experimental data suggesting that in humans, LH is necessary for ovulation but follicular maturation can occur in the presence of FSH alone.

Deletion analysis of the p16 tumour suppressor gene in phaeochromocytomas

BACKGROUND AND OBJECTIVES

The molecular pathogenesis of phaeochromocytoma has not yet been fully established. The p16 tumour suppressor gene is often inactivated in a wide variety of primary human malignancies, including tumours of ectodermal origin. We have therefore examined the status of the p16 gene in a series of phaeochromocytomas.

DESIGN

We studied tumour and constitutive DNA from 26 phaeochromocytoma patients. Twenty-two cases were of sporadic tumours whereas four patients had a hereditary form of the disease. Four tumours were malignant. We performed a semiquantitative multiplex PCR in which the p16 gene was coamplified with an unrelated sequence as an internal control. Standards were constructed by mixing DNA from cell lines with a known p16 status to simulate various degrees of p16 loss. Deletion of the p16 gene was determined by densitometry, measuring the ratio of intensity of the two resulting bands as an indication of the relative abundance of the two templates in the sample.

RESULTS

No homozygous deletion of the p16 tumour suppressor gene was found in any of the phaeochromocytoma samples.

CONCLUSIONS

We have demonstrated that the p16 gene is not deleted in sporadic, hereditary, malignant or benign forms of phaeochromocytomas, and therefore probably does not play a role in the pathogenesis of this tumour. However, because of the small number of malignant cases analysed, we cannot exclude a low frequency of p16 deletions in this subset of tumours.

Mutations in the RET proto-oncogene and the von Hippel-Lindau disease tumour suppressor gene in sporadic and syndromic phaeochromocytomas

Phaeochromocytomas may occur sporadically, or as part of the inherited cancer syndromes multiple endocrine neoplasia (MEN) type 2, von Hippel-Lindau disease (VHL), and, rarely, in type 1 neurofibromatosis. In MEN 2, germline missense mutations have been found in one of eight codons within exons 10, 11, 13, 14, and 16 of the RET proto-oncogene. In VHL, germline mutations within one of the three exons are responsible for the majority of cases. To determine if somatic mutations similar to those seen in the germline in MEN 2 or VHL disease play a role in the pathogenesis of sporadic or familial phaeochromocytomas, we analysed 48 sporadic tumours and tumours from 17 MEN 2 and five VHL patients for mutations in RET exons 9, 10, 11, 13, 14, 15, and 16, and the entire coding sequence of VHL. Five of 48 sporadic phaeochromocytomas had RET mutations within exons 10, 11, and 16. Of these, one was proven to be germline and two were proven to be somatic mutations. Four of 48 had VHL mutations; these included both the bilateral cases in the series (one was proven to be a germline mutation) and two others, of which one was proven somatic.

Molecular and immunohistochemical analysis of P53 in phaeochromocytoma

We searched for mutations of the p53 gene in 25 phaeochromocytomas using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis of the entire conserved region of the gene, encompassing exons 4-8; expression of the p53 protein was assessed by immunohistochemistry. No mutations were found, while a polymorphism in codon 72 was observed. Immunohistochemistry revealed nuclear p53 overexpression in one tumour sample. We conclude that mutations of the 'hotspot' region of the p53 gene do not seem to play a role in the pathogenesis of phaeochromocytoma.

Male pseudohermaphroditism due to a homozygous missense mutation of the luteinizing hormone receptor gene

Leydig cell hypoplasia is a rare autosomal recessive condition that interferes with normal development of male external genitalia in 46,XY individuals. We have studied two Leydig cell hypoplasia patients (siblings born to consanguineous parents), and found them to be homozygous for a missense mutation (Ala593Pro) in the sixth transmembrane domain of the luteinizing hormone (LH) receptor gene. In vitro expression studies showed that this mutated receptor binds human choriogonadotropin with a normal KD, but the ligand binding does not result in increased production of cAMP. We conclude that a homozygous LH receptor gene mutation underlies the syndrome of autosomal recessive congenital Leydig cell hypoplasia in this family. These results have implications for the understanding of the development of the male genitalia.

Low cord blood levels of catecholamine from a newborn of a pheochromocytoma patient

Association of pheochromocytoma and pregnancy is rare and usually related to high maternal and fetal mortality rates. Maternal effects of the tumor have been studied extensively and the clinical outcome has markedly improved during the last decade. However, the role of excess catecholamines on fetal development has been discussed very little. We report here a case of pheochromocytoma during pregnancy. In which catecholamine levels from the cord blood were low despite simultaneous elevated maternal values (1.93 and 29.46 nmol/l norepinephrine, respectively), possibly owing to the high activity of the catecholamine degradative enzymes monoamine oxidase and COMT at the placental level. We suggest that in pregnancies complicated by pheochromocytoma, fetal well-being may be related mainly to good control of maternal blood pressure instead of the amount of catecholamines in the fetal circulation, because the placenta performs a protective role through an effective process of hormone inactivation.

Immunohistochemistry of medullary thyroid carcinoma and C-cell hyperplasia by an affinity-purified anti-human calcitonin antiserum

BACKGROUND

The diagnosis of medullary thyroid carcinoma (MTC) depends on the calcitonin immunohistochemistry. Familial MTC is associated with C-cell hyperplasia (CCH), whereas sporadic MTC is not. A specific and sensitive calcitonin immunohistochemistry is necessary for the diagnosis of MTC and CCH.

METHODS

An affinity-purified anti-calcitonin antiserum (APxCT) was used for immunohistochemistry of the thyroids of 15 patients with MTC. The thyroids of five patients with familial MTC were studied in detail, with each gland sectioned in 48 areas.

RESULTS

Between three and ten independent MTC were found in each thyroid, and CCH was found in all five patients (24.2%, varying from 8.4-56.3% of the 48 areas from each thyroid). MTC and CCH were localized mainly in the middle third and in the central axis of the thyroid lobes. They often were found together in the same area (in a total of 21 areas for the five thyroids sectioned in 48 areas) but ten areas with MTC did not have CCH, and 37 areas with CCH did not have MTC. In ten thyroids partially studied, CCH was indicated in three patients thought to have sporadic MTC. In two thyroids, with follicular and papillary carcinoma, a higher density of C-cells was found around the tumors, but disease was not characterized as CCH.

CONCLUSIONS

APxCT antiserum increased the immunohistochemical specificity and sensitivity. The distinction of the familial from the sporadic MTC requires a careful and extensive search of CCH. C-cells in high density may be found around follicular cell carcinomas, being a potential source of diagnostic error.

The desmopressin stimulation test in the differential diagnosis of Cushing's syndrome

OBJECTIVE

We assessed the ability of desmopressin to stimulate the pituitary-adrenal axis in patients with Cushing's syndrome.

DESIGN AND SUBJECTS

The cortisol response to 5 ot 10 micrograms of intravenous desmopressin was evaluated in 31 patients with Cushing's syndrome of several aetiologies and in 15 normal subjects.

RESULTS

Cortisol responses were observed in 15 out of 16 patients with pituitary dependence and in two patients with adrenal nodular hyperplasia, the increase above baseline ranging from 61 to 379% in the responders. Eight patients with adrenal tumours and one with the ectopic ACTH syndrome did not respond to desmopressin, having shown changes in their cortisol levels from -5 to 42% above baseline. Responses occurred in two out of the 15 normal individuals, whose cortisol increased 58 and 69% above baseline, respectively. Stimulation tests with standard agents as lysine vasopressin or ovine corticotrophin-releasing hormone were performed in the same patients and there was a high degree of concordance. No serious adverse reactions were observed in the tests with desmopressin.

CONCLUSIONS

Desmopressin was able to stimulate the pituitary-adrenal axis in patients with Cushing's disease and, like corticotrophin releasing hormone, it may prove useful in the differential diagnosis of Cushing's syndrome.

Diverse growth hormone receptor gene mutations in Laron syndrome

To better understand the molecular genetic basis and genetic epidemiology of Laron syndrome (growth-hormone insensitivity syndrome), we analyzed the growth-hormone receptor (GHR) genes of seven unrelated affected individuals from the United States, South America, Europe, and Africa. We amplified all nine GHR gene exons and splice junctions from these individuals by PCR and screened the products for mutations by using denaturing gradient gel electrophoresis (DGGE). We identified a single GHR gene fragment with abnormal DGGE results for each affected individual, sequenced this fragment, and, in each case, identified a mutation likely to cause Laron syndrome, including two nonsense mutations (R43X and R217X), two splice-junction mutations, (189-1 G to T and 71 + 1 G to A), and two frameshift mutations (46 del TT and 230 del TA or AT). Only one of these mutations, R43X, has been previously reported. Using haplotype analysis, we determined that this mutation, which involves a CpG dinucleotide hot spot, likely arose as a separate event in this case, relative to the two prior reports of R43X. Aside from R43X, the mutations we identified are unique to patients from particular geographic regions. Ten GHR gene mutations have now been described in this disorder. We conclude that Laron syndrome is caused by diverse GHR gene mutations, including deletions, RNA processing defects, translational stop codons, and missense codons. All the identified mutations involve the extracellular domain of the receptor, and most are unique to particular families or geographic areas.

[Serum growth hormone levels in Hunter's syndrome]

Serum growth hormone (GH) levels were measured in 3 brothers with Hunter syndrome. The secretion of GH was studied by means of insulin (ITT), glucose (GTT), lysine-vasopressin (LVP), and L-Dopa administrations. Mean basal GH levels during the 4 tests were high (x = 14.2 ng/ml) in all cases. In the ITT and LVP tests, GH responses correlated positively with the patients' ages. Contrarily, after L-Dopa administration, GH elevations were normal in the two younger and absent in the oldest case. During GTT, GH levels were suppressed in all cases as expected. Basal cortisol and prolactin serum levels during the tests were normal. In order to clarify these data, GH levels were then determined during 120 min. (20-20 min.) under basal conditions. The means (+/- SD) of GH were 178 +/- 0.15; 4.42 +/- 2.47; and 2.30 +/- 0.71, for cases 1, 2 and 3, respectively (normal values 0-5 ng/ml). Basal somatomedin-C levels were in low-normal ranges. As patients were not undernourished and albumin levels were normal, a slight dysfunction of hypothalamic-pituitary-GH-somatomedin-C axis might occurred in these cases. The hypothesis here offered is that a primary sub-production of somatomedin-C, mainly by liver and kidneys, could be present in Hunter syndrome. This situation would lead to normal-high GH serum levels, as seen in the present cases. GH serum measurements in Hunter syndrome were not documented previously.

Regulation of protein phosphorylation by insulin and insulin-like growth factors in cultured fetal neurons

The pathways depicted in Figure 1 summarize the data discussed in this article. In neurons, the binding of insulin and IGF-I to their respective receptors triggers autophosphorylation of the receptor beta-subunits. IGF-II binds to both neuronal insulin and IGF-I receptors and can stimulate autophosphorylation of either receptor type. In addition to enhancing insulin and IGF-I receptor autophosphorylation, all 3 peptides stimulate the tyrosine phosphorylation of a 70 kDa protein with a similar time course and dose response to receptor phosphorylation. The identity of pp70 is unknown, although the close temporal relationship between pp70 phosphorylation and neurite outgrowth suggests a potential role for this protein. Subsequent to these very early events, two neuronal serine kinases are activated by insulin. One has S6 kinase activity and may represent either the pp90rsk or pp70 class of S6 kinases. Since S6 kinases are activated by direct phosphorylation rather than by second messengers, it is likely that a neuronal S6 kinase kinase exists. The activation of S6 kinase is likely to mediate insulin's effects on neuronal protein synthesis or other growth-related processes. The second serine kinase that is activated by insulin is PKC epsilon. This enzyme is largely restricted to the nervous system, so this signalling pathway may be neuronal-specific. The mechanism of activation of PKC epsilon is unknown, although preliminary data suggests that enhanced phosphorylation of the enzyme is involved. Studies are currently underway to investigate the potential role of diacylglycerol, a potential second messenger generated from either phosphotidylinositol or phosphotidylcholine hydrolysis, in the activation of PKC epsilon by insulin.

Insulin stimulates the activity of a novel protein kinase C, PKC-epsilon, in cultured fetal chick neurons

In this study we examined the effects of insulin on protein kinase C (PKC) activity in cultured fetal chick neurons. PKC activity, measured as 32P incorporation into histone H1 in the presence of calcium (500 microM), phosphatidylserine (100 micrograms/ml), and diolein (3.3 micrograms/ml) minus the incorporation in the presence of calcium alone, was detected in neuronal cytosolic (207 +/- 33 pmol/min/mg) and membrane (33 +/- 8 pmol/min/mg) fractions. Insulin added to intact neurons increased the activity of PKC in both cytosolic and membrane fractions by about 40%. Neurons preincubated with cycloheximide (10 micrograms/ml) 30 min prior to insulin treatment showed the same degree of stimulation of PKC activity by insulin. The activation of PKC was maximal within 5-10 min of insulin exposure and was sustained for at least 60 min. Insulin stimulated PKC in a dose-dependent manner, with a maximal response obtained at 100 ng/ml. Addition of phosphatidylserine and diolein to neuronal cell extracts resulted in the phosphorylation of four major cytosolic proteins (70, 57, 18, and 16 kDa) and one major membrane protein (75 kDa). Phosphorylation of all five proteins was increased 2-fold in extracts from insulin-treated neurons. Immunoblot analysis of whole cell extracts using antibodies against PKC-alpha, PKC-beta, PKC-gamma, PKC-delta, and PKC-epsilon revealed that cultured fetal chick neurons contained only one of these PKC isoforms, the epsilon-isoform. The enzyme was mostly cytosolic. Insulin had no effect on either the amount of distribution of PKC-epsilon in cultured neurons but induced a small change in the mobility of PKC-epsilon on sodium dodecyl sulfate-polyacrylamide gels. When assay conditions were designed to measure specifically the activity of PKC-epsilon, using a synthetic peptide substrate in the absence of calcium, activity was 50 +/- 12% higher in insulin-treated cells (p less than 0.005). PKC activity in control and insulin treated-neurons was almost completely inhibited when assays included a peptide identical to the pseudo-substrate binding site of PKC-epsilon. We conclude that PKC-epsilon is the major PKC isoform present in cultured fetal chick neurons. Insulin stimulates PKC-epsilon activity by a mechanism that does not involve translocation of the enzyme from cytosol to membrane.

[Early detection of medullary thyroid carcinoma in multiple endocrine neoplasia type II]

The early diagnosis of medullary thyroid carcinoma was made in two among six examined siblings belonging to two sibships that were offsprings of multiple endocrine neoplasia type II parents. The calcitonin secretory reserve was determined by a combined test using Ca++ (2 mg/kg) and pentagastrin (0.5 mcg/kg), intravenously. Two abnormal tests made on different days supported the diagnosis. Basal calcitonin levels were moderately high (90-500 pg/ml; NL = 15-85 pg/ml) and peak levels were also abnormal (480-1500 pg/ml; NL less than 320 pg/ml), in both cases. Total thyroidectomy associated to prophylactic resection of lymph nodes from central neck region were performed in both. A small nodule (3-5 mm) was found in each lobe in both cases. Pathological and immunocytochemical data supported the diagnosis of medullary thyroid carcinoma. C-cell hyperplasia was present in the peritumoral zones. Pheochromocytoma and definite hyperparathyroidism were not detected in these cases. Two years after surgery, basal and stimulated serum calcitonin levels remained normal. Carcinoembryonic antigen levels were and continue to be normal, in both. These seem to be the first cases published in this country in which this early diagnosis was made.

[Polyglandular autoimmune type I syndrome with hypoparathyroidism, chronic mucocutaneous candidiasis and intestinal malabsorption]

The occurrence of chronic mucocutaneous candidiasis accompanying polyglandular autoimmune syndrome type I is reported in a female aged 13. Apart the candidiasis, since the age of 3, she had convulsions beginning at 6, cataract at 9, teeth abnormalities, and basal ganglia calcifications. Laboratory data confirmed the diagnosis of hypoparathyroidism. This picture was accompanied by intestinal malabsorption, leading to a state of progressive malnutrition, with intense hypoalbuminemia and anemia. Although the pathophysiology of malabsorption, in these cases, is still not clear, the therapeutic response to pancreatin, in the present case, suggested pancreatic insufficiency, reinforced by the normal d-xylose test and the small intestinal biopsy with inexpressive result.

Insulin receptors mediate growth effects in cultured fetal neurons. II. Activation of a protein kinase that phosphorylates ribosomal protein S6

As an initial attempt to identify early steps in insulin action that may be involved in the growth responses of neurons to insulin, we investigated whether insulin receptor activation increases the phosphorylation of ribosomal protein S6 in cultured fetal neurons and whether activation of a protein kinase is involved in this process. When neurons were incubated for 2 h with 32Pi, the addition of insulin (100 ng/ml) for the final 30 min increased the incorporation of 32Pi into a 32K microsomal protein. The incorporation of 32Pi into the majority of other neuronal proteins was unaltered by the 30-min exposure to insulin. Cytosolic extracts from insulin-treated neurons incubated in the presence of exogenous rat liver 40S ribosomes and [gamma-32P]ATP displayed a 3- to 8-fold increase in the phosphorylation of ribosomal protein S6 compared to extracts from untreated cells. Inclusion of cycloheximide during exposure of the neurons to insulin did not inhibit the increased cytosolic kinase activity. Activation of S6 kinase activity by insulin was dose dependent (seen at insulin concentration as low as 0.1 ng/ml) and reached a maximum after 20 min of incubation. Addition of phosphatidylserine, diolein, and Ca2+ to the in vitro kinase reaction had no effect on the phosphorylation of ribosomal protein S6. Likewise, treatment of neurons with (Bu)2cAMP did not alter the phosphorylation of ribosomal protein S6 by neuronal cytosolic extracts. We conclude that insulin activates a cytosolic protein kinase that phosphorylates ribosomal S6 in neurons and is distinct from protein kinase-C and cAMP-dependent protein kinase. Stimulation of this kinase may play a role in insulin signal transduction in neurons.

Insulin receptors mediate growth effects in cultured fetal neurons. I. Rapid stimulation of protein synthesis

In this study we have examined the effects of insulin on protein synthesis in cultured fetal chick neurons. Protein synthesis was monitored by measuring the incorporation of [3H]leucine (3H-leu) into trichloroacetic acid (TCA)-precipitable protein. Upon addition of 3H-leu, there was a 5-min lag before radioactivity occurred in protein. During this period cell-associated radioactivity reached equilibrium and was totally recovered in the TCA-soluble fraction. After 5 min, the incorporation of 3H-leu into protein was linear for 2 h and was inhibited (98%) by the inclusion of 10 micrograms/ml cycloheximide. After 24 h of serum deprivation, insulin increased 3H-leu incorporation into protein by approximately 2-fold. The stimulation of protein synthesis by insulin was dose dependent (ED50 = 70 pM) and seen within 30 min. Proinsulin was approximately 10-fold less potent than insulin on a molar basis in stimulating neuronal protein synthesis. Insulin had no effect on the TCA-soluble fraction of 3H-leu at any time and did not influence the uptake of [3H]aminoisobutyric acid into neurons. The isotope ratio of 3H-leu/14C-leu in the leucyl tRNA pool was the same in control and insulin-treated neurons. Analysis of newly synthesized proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that insulin uniformly increased the incorporation of 14C-leu into all of the resolved neuronal proteins. We conclude from these data that 1) insulin rapidly stimulates overall protein synthesis in fetal neurons independent of amino acid uptake and aminoacyl tRNA precursor pools; 2) stimulation of protein synthesis is mediated by the brain subtype of insulin receptor; and 3) insulin is potentially an important in vivo growth factor for fetal central nervous system neurons.

[Dynamics of calcitonin secretion in tissue culture of medullary thyroid carcinoma]

Calcitonin secretion dynamics of a medullary thyroid carcinoma in tissue culture was studied by addition of calcium chloride (20 mM), magnesium chloride (20 mM), glucagon (6 x 10(-6) M), and pentagastrin (3 x 10(-6) M). After correction by protein content, calcium caused the greatest release of calcitonin to medium (264%), and glucagon the lowest (48%), in relation to control values. The direct action of glucagon on calcitonin secretion of medullary thyroid carcinoma was confirmed. This system may be also used for testing quimiotherapics acting upon the tumor.

Male pseudohermaphroditism due to nonsalt-losing 3 beta-hydroxysteroid dehydrogenase deficiency: gender role change and absence of gynecomastia at puberty

Adrenal and gonadal functions were evaluated on two adult cousins with male pseudohermaphroditism due to congenital 3 beta-hydroxysteroid dehydrogenase deficiency (3 beta-HSD) without clinical salt-losing. Both patients had been reared as females since birth. Case 1 presented at age 17 with perineal hypospadias virilization without gynecomastia and a female to male gender role change at puberty. Case 2 had previously undergone bilateral orchidectomy in childhood and presented "primary amenorrhea", absence of virilization and a female gender role at the age of 24. In the basal state, as well as after ACTH and hCG stimulation, 3 beta-hydroxy-5-ene-steroid levels were disproportionately elevated, resulting in abnormal 3 beta-hydroxy-5-ene: 3-oxi-4-ene steroids ratios. Normal basal serum cortisol with inadequate cortisol response to ACTH was observed in both patients. Elevated basal plasma renin activity (PRA) and normal basal serum aldosterone (ALDO) were present in both subjects. After ACTH stimulation serum ALDO rose adequately in Case 1 but subnormally in Case 2. Salt restriction resulted in an increase in serum ALDO and no salt loss in Case 1 whereas in Case 2 the substantial rise in PRA and serum ALDO were unable to prevent slight urinary sodium loss. Case 1 had normal basal serum testosterone with subnormal response to hCG stimulation. Incubation of testicular tissue in vitro with [3H]DHEA resulted in large Androstenediol production but diminished testosterone conversion confirming the 3 beta-HSD deficiency in the testes. We conclude that (1) absence of gynecomastia and a female to male gender role change may be observed in the male pubertal presentation of nonsalt-losing 3 beta-HSD deficiency and (2) the different functional behavior of zona glomerulosa in our patients suggests the presence of variable degrees of 3 beta-HSD deficiency in the zona glomerulosa of the nonsalt-losing form.

A clinico-genetic investigation of Leydig cell hypoplasia

We report on a kindred including a patient (46,XY) with typical manifestations of Leydig cell hypoplasia who was born to parents who were first cousins. A sister had secondary amenorrhea possibly due to primary ovarian dysfunction. Analysis of six pedigrees fits to a male-limited autosomal recessive pattern of inheritance; its implication for the mutational dynamics in the populations is evaluated.

X-chromatin in congenital virilizing adrenal hyperplasia

X-chromatin body (XCB) frequencies in oral mucosa were investigated in 14 female patients with the simple non-salt-losing form of congenital virilizing adrenal hyperplasia (CVAH) due to 'partial' 21-hydroxylase deficiency (CVAH-type I), using toluidine blue (TBS) and Feulgen's stains (FS). They were found to be lower than normal controls by both TBS (12.6 +/- 1.73 vs 18.38 +/- 0.41) and FS (13.60 +/- 2.16 vs 17.94 +/- 0.76) methods. After 4-5 weeks on glucocorticoid therapy, XCB frequencies overlapped with those of normal controls using both TBS (16.54 +/- 1.76) and FS (17.09 +/- 1.98). Karyotypes performed in 8 of the 14 cases showed a normal female pattern. Two possible interpretations are proposed: First, variations of XCB counts may reflect the average nuclear size of the cell populations studied. Second, high androgen levels found in untreated cases with CVAH-type I might lead to partial chromosome depiralization and increasing euchromatic areas. At present the first possibility appears more likely.

Familial idiopathic gonadotropin deficiency: a hypothalamic form of hypogonadism

To date, familial idiopathic gonadotropin deficiency (FIGD) has not been delineated as either a hypothalamic or a pituitary form of hypogonadism. Leydig cell sensitivity to human chorionic gonadotropin (HCG) has also been suggested as subnormal in FIGD. Also, in a few previously reported families the Kallmann syndrome was not clearly ruled out. Data herewith reported on three sibs with FIGD supported the following conclusions: 1) FIGD is due to insufficient hypothalamic luteinizing hormone-releasing hormone (LRH) secretion, 2) the sensitivity of Leydig cells to HCG is normal, 3) LRH treatment may be helpful in these patients, 4) an associated hypothalamic-pituitary-prolactin (PRL) dysfunction may also be present, and 5) FIGD and the Kallmann syndrome are different entities having a similar pathophysiology but different cause and overall clinical picture.

Familial dwarfism with high IR-GH: report of two affected sibs with genetic and epidemiologic considerations

Two sibs with high serum IR-GH dwarfism, born to first-cousin parents are described. Genetic analysis based upon 25 reported informative kindreds indicates that the condition has an autosomal recessive pattern of inheritance. Population evaluation and epidemiology of the affected subjects suggest that mutation rates of the gene determining the disease in non-Jewish populations could be as rare as 3.2 x 10(-5). However, its prevalence must be exceptionally high among endogamous Oriental Jewish groups derived from a common gene pool in historical times.

Dyggve-Melchior-Clausen syndrome: genetic studies and report of affected sibs

We report a brother and sister with Dyggye-Melchior-Clausen dysplasia with mental retardation (MR) but as yet without spinal cord injury due to cervical spine abnormality. Mucopolysaccharide metabolism was studied in several ways and was found to be normal. Segregation analysis and study of consanguinity data confirm that both forms of the syndrome--that with MR, and that without MR (Smith-McCort dysplasia) are rare autosomal recessives. Spinal cord injury and early death is a danger in both.

H-Y antigen in Swyer syndrome and the genetics of XY gonadal dysgenesis

The H-Y antigen is a plasma membrane antigen involved in the organogenesis of the mammalian testis. Its expression on human cells is determined by a Y-linked gene. Phenotypic females affected by 46,XY gonadal dysgenesis (Swyer's syndrome) can be either H-Y-positive or H-Y-negative. In this paper we report H-Y antigen and endocrine studies in a sibship with three affected sisters. Immunological studies were performed on two of the patients, and a clearly positive expression was detected in both cases. Endocrine studies consisted in the investigation of the hypothalamic-pituitary-gonadal axis, which revealed that gonadal hormone insufficiency is the only endocrine abnormality associated with the syndrome. A new genetic interpretation and calssification of XY gonadal dysgenesis is proposed.

Recessively inherited, late onset spondylar dysplasia and peripheral corneal opacity with anomalies in urinary mucopolysaccharides: a possible error of chondroitin-6-sulfate synthesis

Two male and two female sibs with an unusual form of spondyloepiphyseal dysplasia were reported. The main clinical features were low stature, moderate shortness of trunk and neck, abnormal span: height ratio, low-normal UBS: LBS ratio, and peripheral corneal punctate opacities only seen by the slitlamp. Normal mental status was present. Typical metachromatic granules were not seen either in bone-marrow cells or in peripheral blood cells. The X-ray picture showed spondylar and pelvic dysplasia. Qualitative rather than quantitative anomalies were shown in the urinary mucopolysaccharides, mostly involving chondroitin-6-sulfate. The genetic data are consistent with autosomal recessive inheritance.

Hormone levels following wedge resection in polycystic ovary syndrome

A study of serum estradiol, progesterone, 17alpha-hydroxy-progesterone, testosterone, dihydrotestosterone, dehydroepiandrosterone (DHA), delta4-androstenedione (delta4-A), FSH, and LH was carried out in one of three sisters having polycystic ovarian disease for a period of 18 days before wedge resection, at the time of surgery, and for 24 days following wedge resection. The mean levels of 17alpha-hydroxyprogesterone, testosterone, DHA, delta4-A, and LH were remarkably elevated prior to wedge resection. There was considerable day-to-day variation. Serum LH varied from 12.5 to 70.5 mIU/ml with a mean of 41.03 +/- 3.55 mIU/ml. Serum estradiol and progesterone levels were generally higher than those found in the early follicular phage. Wedge resection resulted in a fall in serum estradiol, progesterone, 17alpha-hydroxyprogesterone, DHA, and delta4-A. Ovarian secretion of the last four steroids was confirmed by a study of the ovarian vein blood obtained at the time of surgery. An estradiol peak occurred on the 14th post wedge resection day with smaller increases in 17alpha-hydroxyprogesterone, DHA and delta4-A. An increase in serum LH occurred on the 15th post wedge resection day with a peak on Day 16 accompanied by increases in FSH and progesterone. The postovulatory rise of progesterone was accompanied by reduction of serum LH levels to those generally found in the early part of the menstrual cycle. Various hypotheses for the ovulatory failure are discussed.