Multiple Evanescent White Dot Syndrome Associated with Coronavirus Infection: A Case Report

Coronavirus disease 2019 (COVID-19) causes ocular manifestations in approximately 11% of patients. Most patients typically develop ocular symptoms within 30 days of the onset of the first COVID-19 symptoms. The most common ocular manifestation is conjunctivitis, which affects nearly 89% of patients with eye problems. Other much less common anterior segment abnormalities caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are scleritis, episcleritis, and acute anterior uveitis. Posterior segment abnormalities caused by SARS-CoV-2 are mainly vascular, such as hemorrhages, cotton wool spots, dilated veins, and vasculitis. Herein, we report a rare manifestation of COVID-19 and multiple evanescent white dot syndrome (MEWDS) of the retina. In April 2021, a 40-year-old female patient was admitted to the Eye Clinic of Clinical Center of Montenegro (Podgorica, Montenegro). The patient's main complaint was sudden vision impairment, which occurred 14 days after a positive polymerase chain reaction (PCR) test result for SARS-CoV-2 infection. A complete eye examination was performed, followed by fundoscopy, optical coherence tomography (OCT), and fluorescein angiography (FA) tests. The results showed retinal changes associated with MEWDS. The patient underwent additional examinations to rule out common causes of multifocal retinitis, all of which were unremarkable. Therefore, it was concluded that retinitis was a complication of COVID-19. Given its non-invasive nature, fundus examination should be used as a standard screening method for retinal changes in patients with COVID-19.

ACTH and cortisol responses to ghrelin and desmopressin in patients with Cushing's disease and adrenal enlargement

BACKGROUND

Overexpression of ghrelin and vasopressin (V3) receptors demonstrated on corticotrophe adenomas accounts for exaggerated ACTH and cortisol responses to ghrelin and desmopressin (DDAVP) in patients with Cushing's disease (CD).

AIM

In this study we have compared ACTH and cortisol responsiveness to DDAVP and ghrelin in CD patients with and without adrenal enlargement.

SUBJECTS AND METHODS

Ghrelin and DDAVP tests were performed in 15 patients with CD (7 with and 8 without signs of adrenal enlargement) with CRH test in 8 patients. In 7 age and sex-matched healthy subjects, ghrelin test was performed. Plasma ACTH and serum cortisol concentrations were measured after ghrelin, DDAVP and CRH. Growth hormone was measured after stimulation with ghrelin.

RESULTS

Significantly higher baseline and peak ACTH and cortisol concentrations after ghrelin were observed in all patients with CD compared to healthy control subjects. Patients with CD and adrenal enlargement had significantly lower baseline and peak ACTH concentrations after stimulation with ghrelin compared to CD patients without adrenal enlargement, while cortisol levels at baseline and after ghrelin administration were similar. Three out of seven patients with CD and adrenal enlargement did not respond to DDAVP while they responded well to CRH and ghrelin.

CONCLUSION

Patients with CD and adrenal enlargement pose special diagnostic problems. They may have lower baseline ACTH levels and may not respond to DDAVP while they respond to ghrelin and CRH. Despite increased endogenous cortisol levels in CD, cortisol responses to ghrelin and CRH are preserved in patients with CD and adrenal enlargement.

Glucose metabolism during ghrelin infusion in patients with anorexia nervosa

Anorexia nervosa (AN) is an eating disorder characterized by self-induced starvation due to fear of adiposity. Ghrelin, gastric peptide with potent orexigenic, adipogenic, GH-releasing and metabolic properties, is elevated in AN. We have previously shown that intervention with exogenous ghrelin is not effective in terms of inducing neuroendocrine and appetite responses in AN. In this arm of the same study protocol we investigated glucose metabolism responses to 5 h i.v. infusion of active ghrelin in a) 9 severely malnourished AN patients, b) 6 AN patients who partially recovered body weight (PRAN), c) 10 constitutionally thin female subjects with regular menstrual cycles. At baseline, no significant differences were observed in blood glucose, insulin, c-peptide, adiponectin, and homeostasis model assessment index values, between the studied groups. During ghrelin infusions, blood glucose levels significantly increased in all groups although significantly less in low-weight AN; insulin levels were not significantly affected, while c-peptide levels were significantly suppressed only in the constitutionally thin and PRAN subjects. In addition to our previous findings of impaired neuroendocrine and appetite responses in patients with AN, we conclude that metabolic responses to ghrelin are attenuated in these patients, which tend to recover with weight gain.

Plasma ghrelin levels of gastrectomized and vagotomized patients are not affected by glucose administration

BACKGROUND

Ghrelin is a brain-gut peptide with GH-releasing and appetite-inducing activities, secreted mainly by the stomach. Circulating ghrelin concentrations fall rapidly after nutrient ingestion as well as after oral and intravenous glucose challenge. A number of gut hormones including ghrelin require an intact vagal system, which has been hypothesized to have a major role in initiating the postprandial fall in ghrelin levels.

AIM

We aimed to investigate the effect of oral glucose challenge on ghrelin secretion in gastrectomized (GASTRX) and vagotomized patients.

DESIGN

Interventional study.

PATIENTS

Six GASTRX-vagotomized patients and 11 healthy sex- and body mass index (BMI)-matched subjects.

METHODS

An oral glucose tolerance test (OGTT) was performed in all subjects. At baseline, circulating plasma total ghrelin, serum glucose, insulin and GH levels were measured. Serum glucose, insulin, GH and plasma ghrelin levels were determined every 30 min for 2 h.

RESULTS

Plasma ghrelin levels at baseline were reduced by 55% in GASTRX-vagotomized patients compared to the control group (P < 0.01). In control subjects, plasma ghrelin levels decreased significantly during the OGTT whereas in GASTRX-vagotomized patients no reduction was registered (26.4 +/- 2.8% vs. 5.5 +/- 3.4%). The OGTT revealed a significantly greater increase in circulating glucose levels and serum insulin levels while GH response was not different in GASTRX-vagotomized patients compared to control subjects.

CONCLUSIONS

Our data show that circulating ghrelin levels in GASTRX and vagotomized patients were not suppressed after oral glucose administration, unlike control subjects, suggesting that this effect could be due, at least in part, to the lack of contribution of the vagal nervous system to the regulation of ghrelin.

Ghrelin test for the assessment of GH status in successfully treated patients with acromegaly

OBJECTIVE

Posttreatment assessment of disease activity and definition of cure of acromegaly, using measurement of GH secretion, remains problematic. Furthermore, with our efforts to achieve tight biochemical control of the disease it is foreseeable that a proportion of patients may be rendered GH deficient, thus requiring testing for GH deficiency. The aim of our study was to evaluate residual GH secretion in cured patients with acromegaly.

DESIGN AND METHODS

At baseline, circulating GH, IGF-I, IGFBP-3, leptin and lipid (cholesterol and tri-glycerides) levels were measured in 33 acromegalic patients nine years after treatment with surgery of whom 6 were additionally irradiated. Two tests were performed: the GH suppression test--oral glucose tolerance test (OGTT) and the GH provocation test--ghrelin test (1 microg/kg i.v. bolus) and the results were compared with 11 age- and sex-matched control subjects.

RESULTS

According to the consensus criteria (normal IGF-I levels and post-OGTT GH nadir <1 microg/l), 21 treated acromegalic patients were cured, 6 had discordant IGF-I and GH nadir values during OGTT, while 6 had persistent acromegaly. After the GH provocative test with ghrelin (cut-off for severe GH deficiency is GH <3 microg/l), we detected 9 severely GH deficient patients (GHD) among 21 cured acromegalic patients. Mean GH peak (+/-s.e.m.) response to the ghrelin test in GHD acromegalics was significantly lower compared with acromegalics with sufficient GH secretory capacity and control subjects (1.2 +/- 0.2 microg/l vs 20.1 +/- 2.4 microg/l vs 31.1 +/- 2.5 microg/l respectively, P<0.0001). Mean IGF-I and IGFBP-3 levels were not different between GHD and GH-sufficient cured acromegalics. Leptin levels and body mass index (BMI) were significantly higher in GHD male acromegalics compared with GH-sufficient male acromegalics. GHD female acromegalics tended to have higher BMIs while leptin levels were not different.

CONCLUSIONS

The assessment of residual GH secretory capacity by the GH provocation test is necessary in the long-term follow-up of successfully treated acromegalics since a large proportion of these patients are rendered GH deficient.

Ghrelin has partial or no effect on appetite, growth hormone, prolactin, and cortisol release in patients with anorexia nervosa

CONTEXT

Anorexia nervosa (AN) is an eating disorder characterized by self-induced starvation. Gastric hormone ghrelin, potent orexigen, and natural GH secretagogue are increased in AN. Although exogenous ghrelin stimulates appetite, GH, prolactin, and cortisol release in humans, its effects have not been studied, during infusions, in AN patients.

OBJECTIVE

The objective of the study was to determine the effects of ghrelin on appetite, sleepiness, and neuroendocrine responses in AN patients.

DESIGN

This was an acute interventional study.

SETTING

The study was based at a hospital. Investigated

SUBJECTS

Twenty-five young women, including nine patients diagnosed with AN with very low body weight, six AN patients who partially recovered their body weight but were still amenorrheic, and 10 constitutionally thin female subjects, without history of eating disorder, weight loss, with regular menstrual cycles, were included in the study.

INTERVENTION

Each patient received 300-min iv infusion of ghrelin 5 pmol/kg.min and was asked to complete Visual Analog Scale questionnaires hourly.

MAIN OUTCOME MEASURES

Visual Analog Scale scores for appetite and sleepiness, GH, prolactin, and cortisol responses were measured.

RESULTS

At baseline, AN patients had significantly higher ghrelin, GH, and cortisol levels and significantly lower leptin than constitutionally thin subjects. GH responses to ghrelin infusion were blunted in patients with AN. Ghrelin administration did not significantly affect appetite but tended to increase sleepiness in AN patients.

CONCLUSIONS

Ghrelin is unlikely to be effective as a single appetite stimulatory treatment for patients with AN. Our results suggest that AN patients are less sensitive to ghrelin in terms of GH response and appetite than healthy controls. Ghrelin effects on sleep need further studies.

Hypopituitarism as a consequence of traumatic brain injury (TBI) and its possible relation with cognitive disabilities and mental distress

Recent studies have demonstrated that hypopituitarism, in particular GH deficiency, is common among survivors of traumatic brain injury (TBI) tested several months or yr following head trauma. We present the results of endocrine, neurological, neuropsychological and psychiatric evaluation in a group of 67 patients who suffered TBI at least one yr ago. Our study shows that decreased endocrine function is either restricted to one or more anterior pituitary hormones and is present in 34% of patients with any pituitary hormone deficit, while multiple pituitary hormone deficiencies are found in 10% of patients. GH/IGF-I axis was evaluated by GHRH+GHRP-6 test and IGF-I measurement. Severe GHD is the most frequent deficiency present in 15% of TBI patients. Gonadotrophin deficiency was present in 9% of patients with TBI, while thyrotroph and corticotroph function seemed more refractory to impairment. Patients with moderate-to-severe trauma are not necessarily more likely to have hypopituitarism than those with mild injury. Neuropsychological testing revealed a significant positive correlation of peak GH levels after GHRH+GHJRP-6 test with verbal learning and verbal short term memory (RAVLT total score p = 0.06, immediate free recall p = 0.02 and delayed free recall p = 0.04). Verbal and visual memory was significantly lower in elderly patients and in males. Visoconstructional abilities (RCF copy) were significantly lower in the elderly (p < 0.01) and undereducated (p = 0.02). Visual memory (free recall of complex figure after 30 min) significantly correlated with lower IGF-I levels (p = 0.01). Gonadotrophins and testosterone correlated significantly with visoconstructional abilities. Simple and complex conceptual tracking (TMT A and B) was significantly more impaired in older TBI patients (p < 0.01) and with longer time from trauma (TMT B only, p = 0.03). The psychiatric evaluation by using two different scales showed depression, phobic anxiety and psychoticism to be more prominent in the TBI group. Paranoid ideation and somatization negatively correlated with the peak GH responses to GHRH+GHRP-6 test (p = 0.04 and p = 0.03, respectively). Depression scale showed that nearly half of patients suffered from mild to moderate depression. The benefits of hormone replacement therapy on cognitive functioning and mental distress in TBI patients are eagerly awaited.

Gonadotropin response to clomiphene and plasma leptin levels in weight recovered but amenorrhoeic patients with anorexia nervosa

Anorexia nervosa (AN) is a state of leptin and gonadotropin deficiency. Leptin levels are decreased in normal weight women with hypothalamic amenorrhea and leptin may be a sensitive marker of overall nutritional status. The aim of the study is to provide additional information on plasma leptin levels and on gonadotropin responses after clomiphene testing in patients with AN who recovered weight but were still amenorrheic. We evaluated 17 patients with AN, female age 20+/-1.2 yr who reached goal weight [body mass index (BMI) 14.9+/-0.5 to 19.3+/-0.4 kg/m2]. At diagnosis serum leptin levels were 2.2+/-0.1 microg/l while after behavioural therapy and hypercaloric diet for 6-12 months serum leptin levels rose to 6.4+/-1.4 microg/l significantly lower compared with those in the control (no.=10, age 28+/-6.2 yr, BMI 21.1+/-0.3 kg/m2, leptin 9.3+/-0.7 pg/l; p<0.05). None of the patients resumed spontaneous menstrual cycles after weight gain. They were tested with a 10-day administration of clomiphene citrate. All had a significant rise in LH secretion (from 1.7+/-0.3 IU/l to 8.3+/-0.9 IU/l, p<0.01) and serum estradiol levels (from 19.0+/-5.4 to 937.7+/-241.2 pg/ml, p<0.03). Nine out of 17 patients menstruated after clomiphene. Serum leptin levels were not different in those who menstruated from those who did not (6.4+/-1.4 to 6.8+/-1.4 microg/l, p>0.05). Body compositon was studied in 12 additional carefully matched patients with AN who recovered weight. Six of them resumed spontaneous menstrual cycles. Neither BMI, body fat, nor leptin appeared as significant determinants of menstrual status. In conclusion, relative hypoleptinemia persists, independent of fat mass, in weight recovered patients with AN. A normal response to clomiphene in weight-recovered yet still amenorrhoeic patients with AN, offers reassurance that the axis is intact and that the problem lies in the hypothalamus. It is reasonable to believe that nutritional disturbances, fat intake and persisting psychological factors still affect plasma leptin levels and reproductive functions in weight-recovered patients with amenorrhea.

Case report of hypopituitarism with suspected syndrome of inappropriate VP secretion (SIADH) due to a large aneurysm of the internal carotid in the sellar region

Hypopituitarism and hyponatremia, especially when severe, are infrequent findings particularly when the cause of hypopituitarism at presentation is unknown and untreated. Interestingly, hyponatremia is usually seen in elderly patients with hypopituitarism due to various causes. We present a case with unrecognized and untreated hypopituitarism due to a large aneurysm of the internal carotid artery in the sellar region causing the syndrome of inappropriate secretion of antidiuretic hormone (SIADH).

Loss of gender difference in serum leptin levels and its slow recovery after successful surgery for Leydig cell tumours in two virilized females

One of the factors that predicts serum leptin levels is gender. It has been shown that sex steroid hormones, in particular testosterone, play an important role in the regulation of serum leptin levels. We had the opportunity to examine the effects of acute and chronic changes in serum testosterone levels on serum leptin concentrations in two virilized females harbouring testosterone-secreting ovarian tumours, before and after curative surgery. Chronically elevated basal testosterone levels (46 nmol/l) were associated with suppressed serum leptin levels (1.46 microg/l and 2.56 microg/l) vs. 12 age- and BMI-matched healthy subjects 9.89 +/- 0.64 microg/l. Leptin levels were determined from pooled serum samples assayed by commercial radioimmunoassay. High testosterone levels abolished the well known sexual dimorphism of serum leptin levels. Two weeks after curative resection of these tumours serum leptin levels were unaltered and started to increase progressively after one month. One patient received parenteral conjugated oestrogens while the other resumed spontaneous menstrual cycles. Three months after curative surgery obvious changes in body composition were registered (DEXA). Six months later further rise in serum leptin concentrations occurred without further changes in body composition. In conclusion, leptin levels did not change in spite of rapid changes in the steroid milieu, but in the long term increase in body fat stores, new steroid milieu and maybe other factors are important determining factors of serum leptin levels.

Increased incidence of neoplasia in patients with pituitary adenomas. The Pituitary Study Group

OBJECTIVE

The goal of our study was to determine the rate of neoplasms in patients with other pituitary adenomas (non-functioning and prolactinomas) in comparison with acromegaly which is known to favour the development of neoplasia.

DESIGN AND PATIENTS

We reviewed clinical records for 220 patients with acromegaly, 151 patients with non-functioning pituitary adenoma (NF) and 98 patients with prolactinomas. Incidence rates of cancer for patients with pituitary tumours were calculated per person-years of follow-up study. These rates were then compared with sex and age adjusted incidence rates reported by National Tumour Registry. An internal control group of 163 subjects with a non-neoplastic condition, i.e. Graves' disease followed chronically in the same clinic was also studied. The ratios observed to expected were expressed as standardized incidence rates (SIR). The only significant difference between the acromegalic and other pituitary tumours patients was in hypopituitarism, present in 18.2% (acromegaly) 47% (NF) and 18.6% (prolactinomas).

RESULTS

Twenty-three malignant tumours were registered in 19 acromegalics (1 Hodgkin disease, 1 myelogenous leukaemia, 1 lymphocytic leukaemia, 3 papillary thyroid carcinomas, 1 ovarian carcinoma, 2 colorectal carcinoma, 1 renal cell carcinoma, 4 cervical carcinoma, 2 skin cancers, 2 pancreatic carcinoma, 4 breast carcinoma, 1 bladder carcinoma). Three acromegalics harboured two malignancies. Patients with acromegaly had a 3.39-fold increased rate of malignant tumours compared with the general population and a 3.21-fold increased rate compared with our internal control group. Eleven malignant tumours were found in patients with NF-pituitary adenomas and 2 in prolactinoma patients (1 lymphoma, 1 multiple myeloma, 1 colonic cancer, 1 renal cell cancer, 1 stomach cancer, 2 lung cancers, 1 cervix carcinoma, 1 breast cancer, 1 testicular carcinoma and 3 melanoma). Patients with NF pituitary adenomas had a 3.91-fold increased rate of malignant tumours compared with the general population and 4.07-fold increase compared with the internal control group. Patients harbouring prolactinomas did not have an increased incidence rate of malignancy compared with the general population or our internal controls. Female patients with acromegaly and male patients with NF-pituitary adenoma had higher incidences of neoplasia.

CONCLUSION

We have demonstrated that the overall incidence of malignant tumours in patients with non-functioning pituitary adenomas and acromegaly is significantly higher than expected for general population and for our internal control group.

Growth hormone secretion elicited by GHRH, GHRP-6 or GHRH plus GHRP-6 in patients with microprolactinoma and macroprolactinoma before and after bromocriptine therapy

OBJECTIVE

Growth hormone-releasing peptides (GHRPs) are potent GH releasers which act at both pituitary and hypothalamic levels through specific G-protein coupled receptors, recently cloned. A synergistic effect from the simultaneous administration of GHRH + GHRP-6 on GH release is observed in normal subjects, while it is absent in patients with hypothalamo-pituitary disconnection. We studied the effects of GHRH, GHRP-6 and both secretagogues on GH release in patients harbouring pituitary tumours that may be reduced in size by medical treatment.

DESIGN

Analysis of peak GH response to GHRH, GHRP-6 and GHRH plus GHRP-6 in patients with micro- and macroprolactinomas. Integrated GH response over 2 hours calculated as AUG-GH mU/l x 120 min. Analysis of delta PRL above the basal level in response to the same GH releasers.

PATIENTS

Eleven patients with macroprolactinomas aged 41.2 +/- 4.8 years (range 24-75), nine patients with microprolactinomas aged 31.5 +/- 3.4 (range 22-53) and 13 healthy subjects aged 42.1 +/- 4.7 years (range 22-64) were studied. Prolactinoma patients were then treated with bromocriptine (15-20 mg orally) for 6-24 months. Tests were repeated when there was evidence of tumour shrinkage and normalized plasma prolactin concentrations.

RESULTS

Peak GH response before treatment in macroprolactinoma patients was 4.9 +/- 0.9 mu/l after GHRH, 8 +/- 4 mU/l after GHRP-6 and 18 +/- 5 mU/l after GHRH + GHRP-6. Synergism was absent. AUC were 390 +/- 90; 500 +/- 100 and 1100 +/- 300 mU/l x 120 min respectively. These values were all significantly different (P < 0.05) from normal subjects and patients with microprolactinomas with peak GH 16.8 +/- 0.9 mU/l after GHRH; 43 +/- 6 mU/l after GHRP-6 and 130 +/- 10 mU/l after GHRH + GHRP-6. AUC-GH was 1200 +/- 400 after GHRH, 2200 +/- 400 after GHRP-6 and 9000 +/- 1000 mU/l x 120 min after GHRH + GHRP-6. As in normal subjects, synergism was preserved in patients with microprolactinoma (P > 0.05). After treatment with bromocriptine peak GH in patients with macroprolactinoma was 8 +/- 4 mU/l after GHRH, 22 +/- 5 mU/l after GHRP-6 and 70 +/- 20 mU/l after GHRH + GHRP-6. AUC-GH was 800 +/- 300, 1100 +/- 300 and 3500 +/- 800 mU/l x 120 min, respectively. The response of GH after GHRP-6 and GHRH + GHRP-6 improved significantly (P < 0.05) in treated patients with macroprolactinoma. There was no significant change in GH response in microprolactinoma patients after treatment with bromocriptine. Peak GH after GHRH was 30 +/- 20 mU/l, after GHRP-6 it was 75 +/- 8 mU/l and after GHRH + GHRP-6 it was 200 +/- 30 mU/l. AUC-GH was 1500 +/- 700 after GHRH, 4500 +/- 500 after GHRP-6 and 15,100 +/- 600 mU/l x 120 min. Delta prolactin after GHRP-6 did not change before and after bromocriptine treatment in patients with macroprolactinoma or microprolactinoma.

CONCLUSION

GH release after GHRP-6 or GHRH + GHRP-6 is fully preserved in patients with microprolactinomas and does not differ before and after treatment with bromocriptine. Patients with macroprolactinoma have blunted responses of GH after GHRH and GHRP-6 and synergism is severely compromised. GH responsiveness to and synergistic interaction between GHRH and GHRP-6 recovers after shrinkage of macroprolactinoma with bromocriptine. Prolactin release stimulated by intravenous administration of GHRP-6 in healthy subjects was not seen in patients with micro- or macroprolactinomas.

Serum leptin and insulin concentrations in patients with insulinoma before and after surgery

Inferential studies suggest that circulating insulin concentrations positively regulate leptin secretion by adipocytes. In humans, however, insulin requires prolonged periods of time, and relatively artificial set-ups before a relationship with leptin can be observed. In the present work, serum leptin concentrations were measured in five patients with insulinoma before and one month after surgery and in five control subjects matched by sex and body mass index (BMI). The control subjects presented a mean serum leptin concentration of 6.7+/-1.5 microg/l and a BMI of 24.9+/-1.1. The mean serum leptin concentration in patients with insulinoma was 11.8+/-3.1 microg/l (P < 0.05 vs controls), with a BMI of 26.3+/-1.9. After surgery, there was a non-significant reduction in BMI (25.8+/-1.7), and a clear reduction in serum leptin concentration (5.6+/-2.4 microg/l, P < 0.05 vs pre surgical values and no difference vs control subjects). The fasting area under the curve (AUC) of insulin concentration (in mU/l per 120 min) before surgery was 14421+/-4981 and after surgery was 1306-/+171 (P < 0.05). Before surgery, serum leptin concentrations significantly correlated with BMI (r = 0.71) and AUC of insulin (r = 0.82), a correlation that was lost after surgery. In conclusion, serum leptin concentrations are significantly elevated in patients with chronically high insulin levels due to insulinoma. After surgical treatment and normalization of insulin values, leptin levels return to normal.

Growth hormone secretagogues in pathological states: diagnostic implications

The identification and cloning of the receptor for synthetic growth hormone (GH) secretagogues, even before the endogenous ligand has been identified or its precise physiological role established, suggests that there is a novel target of action for this class of drug. In an attempt to select patients who will benefit from GH treatment, GH secretagogues are being evaluated for their usefulness in diagnosing GH deficiency. The effects of GH-releasing peptides (GHRPs) on GH release as a function of age and metabolic status, and in different neuroendocrine pathologies, are described, as are the different mechanisms of action, potency and reproducibility of the response to GHRPs compared with GH-releasing hormone (GHRH). GHRPs offer the advantage over GHRH in natural models of deranged GH secretion in that, in various metabolic states (e.g. obesity, anorexia nervosa and non-insulin-dependent diabetes mellitus), the GH response to GHRH is more impaired than it is to GHRPs. However, in some neuroendocrine pathologies, the reverse is true. Thus, both secretagogues provide separate information on the physiological status of somatotrophs.

Absence of desensitization by hexarelin to subsequent GH releasing hormone-mediated GH secretion in patients with anorexia nervosa

OBJECTIVE

Both the basal levels and the neuroregulation of GH secretion are perturbed in patients with anorexia nervosa. It is unknown if these alterations are due to severe undernutrition or if they reflect basic neurotransmitter alterations of the patient's neural pathways. On the other hand, prior administration of the GH secretagogue hexarelin in normal subjects blocks the GH-releasing capability of GH releasing hormone (GHRH) administered 2 hours later. In the present work a sequential test was performed using the administration of hexarelin as first stimulus followed 120 minutes later by GHRH. The two aims of the study were: (a) to evaluate the interaction of GHRH and hexarelin, and (b) to further understand the alterations in GH neuroregulation in patients with anorexia nervosa.

DESIGN

The GH stimuli used were hexarelin (1 micrograms/kg i.v.), a GH stimulus whose main action is hypothalamic, followed 120 minutes later by GHRH (1 micrograms/kg i.v.) as a pituitary stimulus. Each woman was tested once.

PATIENTS

Thirty-two woman matched for age participated in the study: six normal-weight women as controls, 14 women with anorexia nervosa, seven women with secondary amenorrhoea due to voluntary weight loss for aesthetic reasons, and five normal-weight women after 72 hours of a controlled hypocaloric diet (800 cal/day).

MEASUREMENTS

Plasma GH levels were measured by time-resolved fluoroimmunosasay, each value shown is the mean +/- SE in mU/l.

RESULTS

The administration of hexarelin to the normal-weight women induced a clear-cut GH secretion (expressed as mean +/- SE of GH peak in mU/l of 77.5 +/- 21.8, but blocked the GH-releasing capability of GHRH administered 120 minutes later (6.6 +/- 2.8, P < 0.05). In contrast, the women with anorexia nervosa showed a normal GH response after the two stimuli: hexarelin 64.8 +/- 9.2. GHRH 71.1 +/- 14.2. The absence of heterologous desensitization was specific to anorexia nervosa, because the women with amenorrhoea due to voluntary weight loss but with a normal energy intake showed a pattern similar to the controls (GH after hexarelin 60.3 +/- 9.5 and to GHRH 120 minutes later 6.2 +/- 1.0 (P < 0.05)). Similarly, the women after the short-term hypocaloric diet showed a hexarelin-mediated GH secretion of 99.6 +/- 17.8, which blunted the subsequent administration of GHRH (GH mean peak of 9.9 +/- 2.9, P < 0.05 vs hexarelin).

CONCLUSIONS

In the normal subjects, the administration of hexarelin induced clear-cut GH secretion, but inhibited the action of GHRH when administered 120 min later, while this heterologous desensitization was not observed in the patients with anorexia nervosa. This sequentially delayed test may be of some value in the clinical setting for assessing the status of patients with anorexia nervosa.

Evaluation of pituitary GH reserve with GHRP-6

GH releasing peptides (GHRPs) were developed before the isolation and identification of GH releasing hormone (GHRH) in 1982 yet the clinical era of the GHRPs began in 1988. Since then clinical studies have been greatly extended. We studied the effects of GHRPs on GH release as a function of age, metabolic status and in different neuroendocrine pathologies. The different mechanism of action of GHRPs versus GHRH and the site of action have been addressed. There is a large variability in the stimulatory action of GHRH contrasted with the reproducibility of action of GHRPs. In different metabolic states GH response after GHRH is more impaired than after GHRP-6. On the other hand in different neuroendocrine pathologies GH response after GHRP-6 is more impaired than after GHRH. Each secretagogue provides separate information on GH secretion, necessary not only for linear growth but for general metabolism.

Blocked growth hormone-releasing peptide (GHRP-6)-induced GH secretion and absence of the synergic action of GHRP-6 plus GH-releasing hormone in patients with hypothalamopituitary disconnection: evidence that GHRP-6 main action is exerted at the hypothalamic level

GH-releasing peptide (GHRP-6; His-D Trp-Ala-Trp-D Phe-Lys-NH2) is a synthetic compound that releases GH in a specific and dose-related manner through mechanisms and a point of action that are mostly unknown but different from those of GHRH. In man, GHRP-6 is more efficacious than GHRH, and a striking synergistic action on GH release is observed when GHRP-6 and GHRH are administered simultaneously. Based on such a synergistic action, it has been hypothesized that GHRP-6 acts through a double mechanism by actions exerted both at the pituitary and hypothalamic levels. The aim of the present study was 2-fold: 1) to further characterize the mechanism of action and synergistic effects of GHRP-6; and 2) to study its action in patients with hypothalamopituitary disconnection. Twelve patients with different neuroendocrine pathologies leading to a state of hypothalamopituitary disconnection (functional stalk section) and 11 age- and sex-matched normal controls were studied. Each subject underwent 3 tests on separate occasions, being challenged with GHRH (100 micrograms, i.v.), GHRP-6 (90 micrograms, i.v.), or GHRH plus GHRP-6. GH was analyzed as the area under the curve (mean +/- SE, micrograms per L/120 min). In normal subjects GH secretion was 483.7 +/- 99.2 after GHRH, 1434.8 +/- 393.0 after GHRP-6, and 3771.5 +/- 399.6 after GHRH plus GHRP-6; the level of GH secreted after GHRH plus GHRP-6 treatment was significantly (P < 0.05) higher than after the arithmetic sum of GH levels after both compounds administered separately. In the group of patients with hypothalamopituitary disconnection, the level of GH secreted after GHRH was similar to that in controls (423.4 +/- 62.8); however, a complete blockade was observed after GHRP-6 (97.3 +/- 7.9), significantly (P < 0.05) lower than after GHRH as well as lower than the GHRP-6-induced GH release in control subjects (P < 0.01). After GHRH plus GHRP-6, the patients with hypothalamopituitary disconnection showed severely reduced secretion (745.3 +/- 67.6; P < 0.01 vs. controls), a value that was not significantly different from the arithmetic addition of levels produced by both compounds administered separately.(ABSTRACT TRUNCATED AT 400 WORDS)

GH response to growth hormone releasing hormone and hypoglycaemia is unaltered by high endogenous plasma calcitonin levels in patients with medullary thyroid carcinoma

OBJECTIVE

As it has previously been reported that calcitonin suppresses stimulated growth hormone release, we have studied the serum growth hormone response to growth hormone releasing hormone and insulin-induced hypoglycaemia in patients with high calcitonin levels due to medullary carcinoma of the thyroid.

DESIGN

Growth hormone releasing hormone (100 micrograms i.v.) and insulin (0.15 units/kg i.v.) were given and the growth hormone responses in the patients with medullary carcinoma of the thyroid and normal healthy controls were compared.

PATIENTS

Eight with histologically confirmed medullary thyroid carcinoma, two females and six males, aged 21-77 years, were studied and compared with seven healthy age and sex matched controls.

MEASUREMENTS

Growth hormone and calcitonin were measured.

RESULTS

No significant difference was found between the growth hormone responses observed in patients with medullary carcinoma when compared with normal controls either after GHRH or during insulin-induced hypoglycaemia.

CONCLUSION

We conclude that calcitonin does not alter the pituitary response to GHRH in medullary thyroid carcinoma and is unlikely to play an important role in regulating growth hormone secretion because calcitonin did not modify the release of growth hormone after insulin-induced hypoglycaemia.