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Effect of growth hormone replacement therapy on pituitary hormone secretion and hormone replacement therapies in GHD adults.

OBJECTIVE: We tested the impact of commencement of GH replacement therapy in GH-deficient (GHD) adults on the circulating levels of other anterior pituitary and peripheral hormones and the need for re-evaluation of other hormone replacement therapies, especially the need for dose changes. METHODS: 22 GHD patients were investigated in a double-blind randomized study and 90 GHD patients in an open study at baseline and after 6 and 12 months of GH replacement therapy. RESULTS: In the placebo-controlled trial, the FT(3) levels increased after 6 months in the GH-treated group, and in the open study the FT(3) levels tended to increase. Other hormone concentrations did not change in either part of the study. Four patients required an increase in thyroxine dose, while 2 patients needed dose reduction. One originally euthyroid patient required thyroxine replacement. Two patients with originally conserved pituitary-adrenal function developed ACTH insufficiency. The hydrocortisone dose was increased in 1 and decreased in 1 of the 66 patients with secondary hypocortisolism. None of the females required any adjustment of sex hormone replacement therapy. Two of 37 males needed dose increase of testosterone, while 1 needed dose reduction. CONCLUSION: GH replacement therapy required dose adjustments regarding other hormone replacement therapies in 12.2% (n = 11), while initiation of new hormone replacement was performed in 3.3% (n = 3) of the 90 patients during the 1-year follow-up. Monitoring of pituitary hormone axes is advisable after commencement of GH replacement therapy, since changes of hormone replacement therapy was observed in a small but clinically significant number of patients.

Adult↗

Effects of ovine growth hormone and other anterior pituitary hormones on lipolysis of rat and ovine adipose tissue in vitro.

Ovine growth hormone ( oGH ) was tested for its effects on lipolysis of rat and ovine adipose tissue in vitro. Ovine growth hormone at 1, 5 and 25 micrograms/ml stimulated lipolysis (P less than .05) of chopped rat adipose tissue and isolated rat adipocytes incubated in the presence of 100 mU/ml adenosine deaminase and .2 micrograms/ml dexamethasone, but had no effect on lipolysis of chopped ovine adipose tissue or isolated ovine adipocytes. Isoproterenol, a beta-adrenergic agonist, stimulated lipolysis (P less than .05) of both rat and ovine adipose tissue. Contaminants of the oGH preparation used were examined for lipolytic effects. Thyroid-stimulating hormone (TSH), luteinizing hormone (LH) and adrenocorticotropic hormone (ACTH) content in oGH were measured by radioimmunoassay. When quantities of these hormones contaminating 5 and 25 micrograms oGH were tested for lipolysis in rat adipose tissue, the TSH contamination could account for some (30%) of the lipolysis observed with oGH , while the other hormones had no effect. Also, preincubation of oGH with anti-GH, but not with anti-TSH or anti-LH, removed the principle in oGH responsible for the lipolytic effect on rat adipose tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

Thyrotropin (TSH) beta-subunit gene expression--an example for the complex regulation of pituitary hormone genes.

Synthesis of pituitary hormones was shown to be efficiently regulated at the transcriptional level. The specialized function of the five cell types in the anterior pituitary is controlled by ubiquitous as well as cell-specific transcription factors. Pit-1 is such a cell-specific regulator found only in lacto-, somato- and thyrotropes which could be shown to be essential for basal expression of growth hormone (GH) and prolactin (Prl) genes and the regulated expression of Prl and thyrotropin (TSH) beta-subunit genes. Identification of distinct binding sites for transcription factors and some of the mechanisms of transcriptional control shed light on the complex regulation of pituitary hormone gene expression which is exemplified for the TSH beta gene. The control of basal as well as positively and negatively regulated expression of some pituitary hormone genes becomes fairly well understood by the investigation of the role of Pit-1. Identification of different mutations in the human pit-1 gene supported the role of this protein for combined pituitary hormone deficiency (CPHD) characterized by the deficiency of GH, prolactin and TSH.

Animals↗

The PROP1 2-base pair deletion is a common cause of combined pituitary hormone deficiency.

Combined pituitary hormone deficiency (CPHD) has an incidence of approximately 1 in 8000 births. Although the proportion of familial CPHD cases is unknown, about 10% have an affected first degree relative. We have recently reported three mutations in the PROP1 gene that cause CPHD in human subjects. We report here the frequency of one of these mutations, a 301-302delAG deletion in exon 2 of PROP1, in 10 independently ascertained CPHD kindreds and 21 sporadic cases of CPHD from 8 different countries. Our results show that 55% (11 of 20) of PROP1 alleles have the 301-302delAG deletion in familial CPHD cases. Interestingly, although only 12% (5 of 42) of the PROP1 alleles of our 21 sporadic cases were 301-302delAG, the frequency of this allele (in 20 of 21 of the sporadic subjects given TRH stimulation tests) was 50% (3 of 6) and 0% (0 of 34) in the CPHD cases with pituitary and hypothalamic defects, respectively. Using whole genome radiation hybrid analysis, we localized the PROP1 gene to the distal end of chromosome 5q and identified a tightly linked polymorphic marker, D5S408, which can be used in segregation studies. Analysis of this marker in affected subjects with the 301-302delAG deletion suggests that rather than being inherited from a common founder, the 301-302delAG may be a recurring mutation.

Alleles↗

Primary hyperparathyroidism is associated with an impaired secretion of growth hormone but not of the other anterior pituitary hormones.

We have recently reported that GH secretion is impaired in primary hyperparathyroidism (PHP). No systematic assessment of the whole anterior pituitary function in PHP is available. In this study, anterior pituitary function was evaluated in basal and stimulated conditions in a series of 12 consecutive women with PHP. Serum GH secretion was decreased in 9 of 12 PHP patients (75%) confirming our previous results in different series of PHP patients. Instead, at variance, secretion of all the other anterior pituitary hormones was normal. Thus, PHP is associated with an impaired secretion of GH, but not of the other anterior pituitary hormones. The reason why only GH secretion is affected in PHP is unknown.

Adrenocorticotropic Hormone↗

A mutational hot spot in the Prop-1 gene in Russian children with combined pituitary hormone deficiency.

Combined pituitary hormone deficiency (CPHD), including growth hormone (GH), prolactin (Prl) and thyroid-stimulating hormone (TSH) in children is now considered a heterogeneous syndrome. Recent findings on expression of mouse pituitary-specific homeodomain factors demonstrate dependence of adenopituitary ontogeny on interactive expression of these factors, suggesting their involvement in etiology of CPHD. Prophet of Pit-1 (Prop-1) gene, a novel pituitary-specific homeodomain factor, was analyzed in 14 Russian children with CPHD, in whom Pit-1 gene was intact. We found a mutational hot spot in three patients from two families in homeodomain part of the second exon of Prop-1 gene. The common 2-base pair deletion (GA296) in the homozygous state resulted in a Serine to Stop codon (S109X) substitution and generated a truncated Prop-1 protein. Parents were phenotypically normal and heterozygous for GA296 deletion, indicating an autosomal recessive inheritance. These results demonstrate a novel type of Prop-1 gene mutation as one of the causes of CPHD in Russian patients.

Amino Acid Sequence↗

"Hot spot" in the PROP1 gene responsible for combined pituitary hormone deficiency.

As pituitary function depends on the integrity of the hypothalamic-pituitary axis, any defect in the development and organogenesis of this gland may account for a form of combined pituitary hormone deficiency (CPHD). Although pit-1 was 1 of the first factors identified as a cause of CPHD in mice, many other homeodomain and transcription factors have been characterized as being involved in different developmental stages of pituitary gland development, such as prophet of pit-1 (prop-1), P-Lim, ETS-1, and Brn 4. The aims of the present study were first to screen families and patients suffering from different forms of CPHD for PROP1 gene alterations, and second to define possible hot spots and the frequency of the different gene alterations found. Of 73 subjects (36 families) analyzed, we found 35 patients, belonging to 18 unrelated families, with CPHD caused by a PROP1 gene defect. The PROP1 gene alterations included 3 missense mutations, 2 frameshift mutations, and 1 splice site mutation. The 2 reported frameshift mutations could be caused by any 2-bp GA or AG deletion at either the 148-GGA-GGG-153 or 295-CGA-GAG-AGT-303 position. As any combination of a GA or AG deletion yields the same sequencing data, the frameshift mutations were called 149delGA and 296delGA, respectively. All but 1 mutation were located in the PROP1 gene encoding the homeodomain. Importantly, 3 tandem repeats of the dinucleotides GA at location 296-302 in the PROP1 gene represent a hot spot for CPHD. In conclusion, the PROP1 gene seems to be a major candidate gene for CPHD; however, further studies are needed to evaluate other genetic defects involved in pituitary development.

Adrenocorticotropic Hormone↗

Multiple pituitary hormone gradients from cavernous sinus sampling in patients with Cushing's disease.

OBJECTIVE: Cavernous sinus sampling in patients with adreno-corticotropic-hormone (ACTH) secreting pituitary adenomas has been used to identify directly ACTH hypersecretion from the pituitary and to predict the lateralization of a microadenoma. In our previous series, cavernous sinus sampling provided a sufficient central/peripheral (c/p) ratio of ACTH and the correct laterality of the pituitary lesion in all microadenomas situated in the lateral wing. To clarify the diagnostic value of other anterior pituitary hormones in relation to ACTH gradients, we evaluated multiple pituitary hormone gradients between a cavernous sinus and a peripheral vein and between both cavernous sinuses in patients with Cushing's disease. METHODS: Cavernous sinus sampling was done in 11 patients with clinical and biochemical features of ACTH-dependent Cushing's syndrome. In 9, pituitary adenoma was detected during trans-sphenoidal surgery and histologically confirmed, while 2 others were suspected of having ectopic lesions. Serum ACTH, prolactin (PRL), thyroid stimulating hormone (TSH), growth hormone (GH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) from catheters in both cavernous sinuses and from a peripheral vein were measured. The c/p ratios of each hormone and the intercavernous gradients were evaluated. RESULTS: The c/p ratio of ACTH indicated the presense of pituitary lesions in all 9 patients with ACTH-secreting microadenomas. In addition, the intercavernous gradients of ACTH indicated the correct localization of microadenomas in all 6 patients with lateralized lesions. As for other hormones, the c/p ratios of GH, PRL, TSH and LH were significantly high in number 7, 6, 6 and 3 patients, respectively. In contrast, the significant step up of FSH was observed only in one patient. The intercavernous gradients of GH and PRL were significantly high in number 5 and 4 patients, respectively. CONCLUSIONS: The intercavernous gradients of GH and PRL tend to indicate the lateralization of a microadenoma. The measurement of GH and PRL during cavernous sinus sampling may provide additional information, in the lateralization of ACTH-secreting microadenomas.

Adenoma↗

The catecholamine response to hypoglycemia in children with isolated growth hormone deficiency syndromes and multiple pituitary hormone defects.

We examined the catecholamine response to insulin-induced hypoglycemia in 46 short children evaluated for growth hormone (GH) deficiency by both pharmacologic stimulation and integrated concentration of GH. Twelve patients had quantitatively normal GH secretion by both pharmacologic stimulation and integrated concentration of GH (GHNORM). Twenty-two patients had normal GH to pharmacologic stimulation but subnormal integrated concentration of GH (GHND). Twelve patients had GH deficiency by both tests (GHD): six had isolated GH deficiency (GHD type 1) and six had multiple hormone deficiencies (GHD type 2). There was no significant difference between the peak epinephrine, norepinephrine, and cortisol responses of GH-NORM, GHND, and GHD type 1 patients. The mean peak epinephrine response of GHD type 2 patients was significantly lower (564 +/- 561 pg/ml, p less than 0.03) compared to the other patient groups. There was no significant difference between the peak norepinephrine levels between GHD type 2 patients and the remaining groups. There was no correlation between decrease in blood glucose and either increase in growth hormone, catecholamine, or cortisol concentrations. There was a significant correlation between log peak epinephrine and peak cortisol response (r = 0.53, p less than 0.0002) of the 46 subjects. Neither the basal nor stimulated catecholamine levels correlated with the integrated concentration of cortisol. We conclude that isolated GH deficiency is not associated with impairment of the catecholamine response to hypoglycemia; impairment of the epinephrine response to hypoglycemia is only associated with multiple pituitary hormone deficiencies; in children, the degree of glucose lowering is not correlated with the magnitude of peak GH, catecholamine, or cortisol responses.

Adolescent↗

The cell adhesion molecules N-cadherin and neural cell adhesion molecule regulate human growth hormone: a novel mechanism for regulating pituitary hormone secretion.

Pituitary GH secretion is regulated by hypothalamic hormones and peripheral factors. Cell-cell contact may also have an important role in regulating pituitary hormone expression and secretion. The role of pituicyte cell-cell contact mediated by N-cadherin and neural cell adhesion molecule (N-CAM) was studied in the regulation of GH secretion. RT-PCR showed N-cadherin mRNA expression in eight of 12 of GH-secreting adenomas compared with one of seven of prolactin-cell adenomas. N-cadherin and N-CAM were similarly expressed in adenomas and in adult and fetal normal pituitary tissues. The effects of CAM homophilic binding on GH secretion from dispersed human fetal pituitary cultures were studied by manipulating CAM mediated cell-cell contact using either soluble N-cadherin-Fc or pituitary cells cocultured with NIH-3T3 cells stably expressing CAMs. CAM stimulation increased GH secretion from pituitary fetal cultures by 40-60% (P < 0.05) and also from cultured GH adenoma cells by 40-75% (P < 0.05). Disrupting N-cadherin homophilic binding by anti-N-cadherin antibody decreased fetal, but not tumorous GH secretion by 40% (P < 0.05). This study indicates that pituitary cell-cell contact mediated by homophilic interactions between adhesion molecules regulates human GH secretion.

3T3 Cells↗

Anterior pituitary hormones in plasma and pituitaries from patients with Cushing's disease.

Pituitary adenomas were obtained from eight of nine patients with Cushing's disease, and the surrounding tissues as well were obtained from six of nine patients. ACTH, beta-lipotropin (beta-LPH), beta-endorphin, GH, TSH, LH, and PRL concentrations in these tissues were determined by RIA. Immunoreactive ACTH and beta-endorphin (beta-endorphin + beta-LPH) were present in high concentrations in all adenomas, and low concentrations were found in the surrounding tissues, except for one patient. As compared to levels seen in normal pituitary tissue, the GH concentration in the surrounding tissues was suppressed in five of six cases. TSH and LH concentrations were suppressed in four and three cases, respectively. The PRL concentration was not suppressed in any of the six patients studied. These four hormones were not detected in any adenoma. Plasma GH, TSH, and LH responses to various stimuli which were suppressed preoperatively returned to normal in most of the patients after adenomectomy. Basal plasma cortisol concentrations were normal or subnormal and were suppressed by the administration of 1 mg dexamethasone after adenomectomy, in contrast to the lack of such suppression preoperatively. ACTH and beta-endorphin secretion were stimulated by lysine-8-vasopressin and suppressed by dexamethasone and cyproheptadine in vitro.

Adenoma↗

Vasopressin as a neuroendocrine regulator of anterior pituitary hormone secretion.

Secretion of the anterior pituitary hormones adrenocorticotropin (ACTH), beta-endorphin and prolactin (PRL) is complex and involves a variety of factors. This review focuses on the involvement of arginine-vasopressin (AVP) in neuroendocrine regulation of these anterior pituitary hormones with special reference to receptor involvement, mode of action and origin of AVP. Arginine-vasopressin may act via at least two types of receptors: V1- and V2-receptors, where the pituitary V1-receptor is designated V1b. The mode of action of AVP may be mediating, i.e. anterior pituitary hormone secretion is transmitted via release of AVP, or the mode of action may be permissive, i.e. the presence of AVP at a low and constant level is required for anterior pituitary hormones to be stimulated. Under in vivo conditions, the AVP-induced release of ACTH and beta-endorphin is mainly mediated via activation of hypothalamic V1-receptors, which subsequently leads to the release of corticotropin-releasing hormone. Under in vitro conditions, the AVP-stimulated release of ACTH and beta-endorphin is mediated via pituitary V1b-receptors. The mode of action of AVP in the ACTH and beta-endorphin response to stress and to histamine, which is involved in stress-induced secretion of anterior pituitary hormones, is mediating (utilizing V1-receptors) as well as permissive (utilizing mainly V1-but also V2-receptors). The AVP-induced release of PRL under in vivo conditions is conveyed mainly via activation of V1-receptors but V2-receptors and probably additional receptor(s) may also play a role.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗