Panhypopituitarism: genetic versus acquired etiological factors.

OBJECTIVE: Mutations in the genes encoding pituitary transcription factors (mainly PROP1, POUF1 and HESX1) are responsible for familial combined pituitary hormone deficiency (CPHD) and septo-optic dysplasia (SOD) while only a low percentage of mutations are the cause of sporadic forms. Indeed, it has been suggested that environmental rather than genetic factors could be important in the pathogenesis of CPHD. PATIENTS AND METHODS: Thirty-six sporadic patients diagnosed with CPHD or SOD were included in the study. All coding exons and intron-exon boundary regions of PROP1, POUF1 and HESX1 were amplified by PCR and subsequently sequenced. RESULTS: Two novel missense mutations in the HESX1 gene (Q117P, K176T) were identified in two patients. Polymorphisms in PIT1 and PROP1 were also detected. A higher percentage of breech delivery in male patients with CPHD versus females was observed. CONCLUSIONS: The low percentage of mutations found in the most common transcription factors involved in CPHD show that a better characterization of hormonal and morphological phenotypes is necessary for patients with CPHD included in genetic studies, and other genetic or non-genetic factors have to be taken into account.

Circulating non-22 kDa growth hormone isoforms after a repeated GHRH stimulus in normal subjects.

The aim of this study was to evaluate the proportion of non-22 kDa GH isoforms in relation to total GH concentration after a repeated GHRH stimulus in healthy subjects. We studied 25 normal volunteers (12 males and 13 females, mean age 13.1 years, range 6-35), who received two GHRH bolus (1.5 mug/kg body weight, i.v.) administered separately by an interval of 120 minutes. The proportion of non-22 kDa GH was determined by the 22 kDa GH exclusion assay (GHEA), which is based on immunomagnetic extraction of monomeric and dimeric 22 kDa GH from serum, and quantitation of non-22 kDa GH isoforms using a polyclonal GH assay. Samples were collected at baseline and at 15-30 min intervals up to 240 min for total GH concentration. Non-22 kDa GH isoforms were measured in samples where peak GH after GHRH was observed. Total GH peaked after the first GHRH bolus in all subjects (median 37.2 ng/ml; range: 10.4-94.6). According to GH response to the second GHRH stimulus, the study group was divided in "non-responders" (n=7; 28%), with GH peak levels lower than 10 ng/ml (median GH: 8.7 ng/ml; range 7.3-9.6) and "responders" (n=18; 72%), who showed a GH response greater than 10 ng/ml (median 17 ng/ml; range 10.1-47.0). The median proportion of non-22 kDa GH on the peak of GH secretion after the first GHRH administration was similar in both groups ("responders" median: 8.6%, range 7-10.9%; "non-responders" median: 8.7%, range 6.7-10.3%), independently of the type of response after the second GHRH. In contrast, the median proportion of non-22 kDa GH was greater at time of GH peak after the second GHRH bolus in the "non-responders" (median 11.4%; range 9.1-14.3%) in comparison with the "responders" (median 9.1%; range 6.7-11.9%; p=0.003). A significant negative correlation between the total GH secreted and the percentage of non-22 kDa isoforms was seen in the "non-responders" (p=0.003). These differences in GH response to repeated GHRH stimulation and in the pattern of GH isoforms at GH peak among subjects might be due to distinct recovery patterns of somatrotrophic function and/or differences in metabolic clearance of GH isoforms.

Dual growth hormone (GH) response to repeated GH releasing hormone stimulus in children and adults.

Several authors have demonstrated that plasma growth hormone (GH) levels as response to acute GH releasing hormone (GHRH) stimulation in adults are decreased by a previous GHRH injection whereas they are maintained in children. Probably the most accepted hypothesis for this finding is the increase in the somatostatinergic tone. The aim of the present study was to evaluate the dual GH response to repeated GHRH stimuli to clarify the possible influence of somatostatinergic activity in the type of response. Eighteen healthy prepubertal children, mean age 9.2 years (range: 6.0-12.9 years) and 19 healthy adult volunteers, mean age 25.5 years (range: 17-35 years) were studied with the GHRH test. An additional group of 10 normal adults with similar characteristics (mean age 31 years, range 25-35 years) were also recruited as a control group for somatostatinergic assessment. The GH response to the first GHRH bolus was similar in both children and adults. However, while children showed a preserved response to the second stimulus, it was diminished in adults. As expected, thyroid stimulating hormone (TSH) was within the normal range in all subjects. When the evolution of TSH was compared between the group of non-responders and the control group, no significant differences were found either at basal time or at 120 min, showing a similar decreasing trend for serum TSH level. The variation of TSH levels were also expressed as the proportion of TSH response after 2 hours compared to the basal level (TSH-120/TSH-0) but no significant differences were found (GHRH non-responders group mean: 73.6%, range: 51.3-93.7; control group mean: 70.7%, range: 62.9-92.5). In conclusion, the results confirm that in adults but not in children, the somatotrope responsiveness to GHRH is inhibited by a previous bolus of GHRH. The finding that the plasma TSH level diminishes in a similar manner in both non-responders and the control group is in agreement with the rejection of the hypothesis of the influence of somatostatin.

Effect of cyclic 3',5'-adenosine monophosphate, glucocorticoids, and insulin on leptin messenger RNA levels and leptin secretion in cultured human trophoblast.

Leptin is a polypeptide hormone originally thought to be produced exclusively by adipocytes. However, both leptin mRNA and leptin protein were identified in human placental trophoblast cells, suggesting a potential role in human pregnancy. In the present report, we examined the regulation of leptin mRNA levels and secretion by cAMP, glucocorticoids, and insulin in term human placental tissue. Placentae were obtained immediately after delivery from mothers with uncomplicated pregnancies. Leptin concentrations were measured by ELISA in the cultured media of trophoblast maintained in monolayer culture for 24, 48, and 72 h. Likewise leptin mRNA levels in these cultured human trophoblast cells were determined by reverse transcription-polymerase chain reaction. Treatment with forskolin and (Bu)(2) cAMP led to a time- and dose-dependent increase in leptin release, significant after 48 and 72 h. Moreover, incubation with forskolin for 48 h also clearly increased leptin mRNA concentration. Leptin secretion and mRNA levels were also assessed after treatment with insulin or dexamethasone. We found a time- and dose-dependent increase in leptin release, significant after 48 and 72 h. Leptin mRNA levels were also increased after these treatments. All this supports a stimulatory role of cAMP pathway, insulin and dexamethasone in the leptin mRNA levels, and leptin release in trophoblast cells in vitro.

Influence of sex and age at onset on autoantibodies against insulin, GAD65 and IA2 in recent onset type 1 diabetic patients.

METHODS: Autoantibodies against insulin (IAA), glutamic acid decarboxylase (GADA) and tyrosine phosphatase IA2 (IA2A) were measured in sera from 448 recent onset patients with type 1 diabetes mellitus (DM) subdivided according to sex (194 female and 254 male) and age at onset (134 patients diagnosed before 10 years, 187 between 10 and 20 years, 66 between 20 and 30 years and 61 over 30 years. RESULTS: Autoantibodies were more frequent in female DM patients (93.8 vs. 86.6%, p = 0.013) due to an increased prevalence of both GADA (86.1 vs. 70.1%) and IA2A (59.3 vs. 49.2%), with GADA levels also significantly higher in women (0.24 vs. 0.18 U, p = 0.0003). When age groups were compared, there was a reduction in prevalence in patients over 20 years for both IAA (70% for patients diagnosed under 20 and 36% for older patients) and IA2A (65 and 25%, respectively). These differences also affected IAA levels, with the highest antibody titres in the youngest group (1,214.1 nU/ml in children under 10 compared to 546.9, 345.6 and 341.1 nU/ml in the subsequent groups; p < 10(-4)). GADA prevalence did not differ significantly between age groups but, nevertheless, autoantibody levels were highest among the oldest type 1 DM patients (0.327 U compared to 0.216, 0.197 and 0.176 U in the decreasing age groups; p < 10(-4)). CONCLUSION: There are sex- and age-related differences affecting the presence and/or titres of beta cell autoantibodies. We speculate that these differences could reflect the severity and specificity of the autoimmune attack against the endocrine pancreas and might influence the rate of progression to type 1 DM or the risk of developing other autoimmune diseases.

Hypothalamic-pituitary-testicular function in 70 patients with myotonic dystrophy.

Hypothalamic-pituitary-testicular function was studied in 70 patients with myotonic dystrophy (MD). The diagnosis was confirmed by electromyography. The mean age of the patients was 36.2 +/- 13.2 yr and the duration of the disease was 11.17 +/- 8.01 yr. Testicular atrophy (testes less than or equal to 12 ml on a Prader orchidometer) was present in 65.5% of patients. Fertility among married patients was 66.6%. Mean testosterone plasma levels were 438 +/- 298 ng/dl vs 520 +/- 185 ng/dl in the control group (P = NS). Basal plasma FSH and LH levels, and their response after the administration of 100 mcg of LH-RH were significantly increased although a wide dispersion was observed. Sperm count was carried out in 27 cases, showing a normal count in 7, oligospermia in 12, and azoospermia in 8 patients. Testicular biopsy was performed in 45 patients being normal in 2, showing mild testicular damage in 8, moderate in 14, and severe in 18; it was nule in 3 of them. A significant relationship between testicular atrophy and the sperm count (p less than 0.01), testicular damage and testicular atrophy (p less than 0.025), and sperm count and testicular damage (p = 0.017) was found. Basal plasma FSH and LH level were significantly related to the degree of damage in the testicular biopsy. All these findings indicate a primary testicular pathology, prevailing tubular over interstitial damage. We have not found any association between the duration of the disease and gonadal dysfunction.