Dose-response relationship between plasma ACTH and serum cortisol in the insulin-hypoglycaemia test in 25 healthy subjects and 109 patients with pituitary disease

Evaluation of growth hormone deficiency in women with unexplained infertility

PURPOSE

Growth hormone (GH) has been recognized to play a regulatory role in female reproduction. It has been reported that infertile GH deficient patients regained fertility after GH replacement. The frequency of GH deficiency is not established in patients diagnosed with unexplained infertility. Here, we aim to present the prevalence of GH deficieny in this patient group.

METHODS

We included patients diagnosed with unexplained infertility throughout 18 months. Insulin tolerance test (ITT) and glucagon stimulation tests (GST) were performed and insufficient response to both tests was required for the diagnosis of GH deficiency.

RESULTS

Twenty-five patients were included in the study, the mean age was 27.4 ± 4.5 years and the median duration of infertility was 60 months (min:14, max:120). Two patients were GH deficient according to GST and 14 to ITT. Two patients (8%) showed lack of response on both tests and were diagnosed with GH deficiency.

CONCLUSION

The rate of GH deficiency among women with unexplained infertility was 8% in this preliminary study. There is need for further studies with larger patient groups to verify the results.

Can a glucagon stimulation test characterized by lower GH cut-off value be used for the diagnosis of growth hormone deficiency in adults?

OBJECTIVE

The aim of this study was to assess diagnostic values of insulin tolerance test (ITT), glucagon stimulation test (GST), and insulin like growth factor-I (IGF-I) level, to find optimal GH cut-off values for GST, and to evaluate efficiencies of patient age, gender, body-mass index (BMI), and additional pituitary hormone deficiencies (PHDs) in the diagnosis of growth hormone deficiency (GHD).

STUDY DESIGN

This retrospective study involved 216 patients with a pituitary disease and 26 healthy controls. Age, gender, BMI, medical histories, and hormonal data including baseline and stimulated hormone values were evaluated. Three cut-off values for peak GH responses to stimulation tests were evaluated: (a) 3.00 µg/L on ITT, (b) 3.00 µg/L on GST, and (c) 1.07 µg/L on GST.

RESULTS

According to the ITT, GST with 3.00 µg/L cut-off, and GST with 1.07 µg/L cut-off, GHD was present in 86.1, 74.5, and 54.2 % patients, respectively. Patient age, BMI, and number of PHDs, but not gender, were found to be correlated with IGF-I and peak GH concentrations. All patients with an IGF-I concentration ≤95 ng/ml or ≥3 PHD had GHD. None of the patients with adequate GH response to the GST with 1.07 µg/L cut-off, but blunted responses to ITT and GST with 3.00 µg/L cut-off, had ≥3 PHDs. 12 out of 26 (46.2 %) healthy subjects failed the GST with 3.00 µg/L cut-off, but not with 1.07 µg/L cut-off.

CONCLUSIONS

Patient age, IGF-I, BMI, and number of PHDs are efficient factors associated with the diagnosis of GHD. A 4 h GST with a diagnostic GH threshold of 1.07 µg/L seems to be a good diagnostic method for GHD.

Clinical factors associated with biochemical adrenal-cortisol insufficiency in hospitalized patients

BACKGROUND

Diagnosis of adrenal-cortisol insufficiency is often misleading in hospitalized patients, as clinical and biochemical features overlap with comorbidities. We analyzed clinical determinants associated with a biochemical diagnosis of adrenal-cortisol insufficiency in non-intensive care unit (ICU) hospitalized patients.

METHODS

In a retrospective cohort study we reviewed 4668 inpatients with random morning cortisol levels ≤15 μg/dL hospitalized in our center between 2003 and 2010. Using serum cortisol threshold level of 18 μg/dL 30 or 60 minutes after Cortrosyn (250 μg; Amphastar Pharmaceuticals, Inc., Rancho Cucamonga, Calif) injection to define biochemical adrenal-cortisol status, we characterized and compared insufficient (n = 108, serum cortisol ≤18 μg/dL) and sufficient (n = 394; serum cortisol >18 μg/dL) non-ICU hospitalized patients.

RESULTS

Commonly reported clinical and routine biochemical adrenal-cortisol insufficiency features were similar between insufficient and sufficient inpatients. Biochemical adrenal-cortisol insufficiency was associated with increased frequency of liver disease, specifically hepatitis C (P = .01) and prior orthotopic liver transplantation (P <.001), human immunodeficiency virus (HIV; P = .005), and reported pre-existing male hypogonadism (P <.001), as compared with the biochemical adrenal-cortisol sufficiency group. Forty percent of insufficient inpatients were not treated with glucocorticoids after diagnosis. Multivariable logistic analysis demonstrated that inpatients with higher cortisol levels (P = .0001) and higher diastolic blood pressure (P = .05), and females (P = .009) were more likely not to be treated, while those with previous short-term glucocorticoid treatment (P = .002), other coexisting endocrine diseases (P = .005), or who received an in-hospital endocrinology consultation (P <.0001), were more likely to be replaced with glucocorticoids.

CONCLUSIONS

Commonly reported adrenal-cortisol insufficiency features do not reliably identify hospitalized patients biochemically confirmed to have this disorder. Comorbidities including hepatitis C, prior orthotopic liver transplantation, HIV, and reported pre-existing male hypogonadism may help identify hospitalized non-ICU patients for more rigorous adrenal insufficiency assessment.

History of stress-related health changes: a cue to pursue a diagnosis of latent primary adrenal insufficiency

OBJECTIVE

Routine delays in the diagnosis of primary adrenal insufficiency (PAI) are well known and conceivably attributable to the absence of cues, other than anti-adrenal autoantibodies, to pursue subclinical PAI. Subclinical PAI is latent unless the afflicted patient encounters stress such as an acute illness, surgery, psychosocial burden, etc. It remains to be demonstrated whether a history of stress-related health changes is a useful cue to pursue a diagnosis of latent PAI.

METHODS

The patients were selected for a history of recurrent symptoms, i.e., gastrointestinal symptoms, fatigue, or lassitude, aggravated by stress and alleviated by the removal of stress, and signs, i.e., weight loss, hypotension, and hyperpigmentation. As the early morning cortisol levels were low or low-normal and the adrenocorticotropic hormone (ACTH) levels were within the reference ranges, provocation tests, i.e., insulin-induced hypoglycemia tests and low-dose (1 μg) corticotropin tests (LDTs), were used to estimate the hypothalamus-pituitary-adrenal (HPA) axis status. Patients with the HPA axis dysfunction on two provocation tests were supplemented with physiologic doses of glucocorticoids (GCs). The effects of GC supplementation on stress-related health changes were observed.

RESULTS

The ACTH levels after insulin-induced hypoglycemia were higher and the cortisol levels were lower in the patients than in the control subjects. The cortisol levels in the patients were increased less significantly by LDT than those observed in the control subjects. Stress-related health changes ceased to recur and signs, i.e., a low body weight, hypotension, and hyperpigmentation, were ameliorated following GC supplementation.

CONCLUSION

A history of stress-related health changes is useful as a cue to pursue latent PAI in patients with low or low-normal early morning cortisol levels.

The impact of traumatic brain injury on pituitary function

It is paramount that clinicians who care for patients with traumatic brain injury (TBI) at any point in time, including neurosurgeons, rehabilitation physicians, internists, neurologists, and endocrinologists, are aware of the prevalence of posttraumatic hypopituitarism and its impacts on acute and long-term recovery. This article reviews the natural history, pathophysiology, and presenting features of hypopituitarism occurring after TBI. Proposed methodologies for screening, diagnosis, and initiation of treatment are discussed, as well as the effect of hormone replacement therapy on clinical outcomes.

Selective use of the insulin tolerance test to diagnose hypopituitarism

The insulin tolerance test is considered the gold standard for assessing the hypothalamic-pituitary-adrenal and growth hormone (GH) axes, but its use varies considerably among different endocrine units. We recommend using the insulin tolerance test to assess the hypothalamic-pituitary-adrenal axis within 3 months of pituitary surgery, where adrenocorticotropic hormone 1-24 testing is equivocal, and to assess for GH deficiency where the patient is being considered for GH replacement therapy. We also discuss safety issues, how to ensure adequate hypoglycaemia and possible alternative tests, such as the overnight metyrapone test and glucagon test.

Hypopituitarism in the elderly

Pituitary dysfunction in elderly can represent a true diagnostic and therapeutic challenge to clinicians caring for these patients. Symptoms associated with partial or total hypopituitarism, such as fatigue, lower muscle strength and decreased libido, are nonspecific and can be often attributed to normal aging. Gold standard pituitary diagnostic testing carries higher risks in elderly and is classically replaced by alternative testing. Furthermore, the benefits and safety of selective pituitary hormonal replacement, specifically sexual and growth hormone replacement, remain subject of controversy in this group of patients. Recognizing and appropriately treating hypopituitarism in elderly is crucial for the survival and well being of the older patients with this disease.

Synaptic regulation of the hypothalamic-pituitary-adrenal axis and its modulation by glucocorticoids and stress

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis has been implicated in a range of affective and stress-related disorders. The regulatory systems that control HPA activity are subject to modulation by environmental influences, and stressful life events or circumstances can promote subsequent HPA dysregulation. The brain is a major regulator of the HPA axis, and stress-induced plasticity of the neural circuitry involved in HPA regulation might constitute an etiological link between stress and the development of HPA dysregulation. This review focuses on the synaptic regulation of neuroendocrine corticotropin-releasing hormone (CRH) neurons of the hypothalamic paraventricular nucleus, which are the cells through which the brain predominantly exerts its influence on the HPA axis. CRH neuronal activity is largely orchestrated by three neurotransmitters: GABA, glutamate, and norepinephrine. We discuss our current understanding of the neural circuitry through which these neurotransmitters regulate CRH cell activity, as well as the plastic changes in this circuitry induced by acute and chronic stress and the resultant changes in HPA function.

Synaptic regulation of the hypothalamic-pituitary-adrenal axis and its modulation by glucocorticoids and stress

Dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis has been implicated in a range of affective and stress-related disorders. The regulatory systems that control HPA activity are subject to modulation by environmental influences, and stressful life events or circumstances can promote subsequent HPA dysregulation. The brain is a major regulator of the HPA axis, and stress-induced plasticity of the neural circuitry involved in HPA regulation might constitute an etiological link between stress and the development of HPA dysregulation. This review focuses on the synaptic regulation of neuroendocrine corticotropin-releasing hormone (CRH) neurons of the hypothalamic paraventricular nucleus, which are the cells through which the brain predominantly exerts its influence on the HPA axis. CRH neuronal activity is largely orchestrated by three neurotransmitters: GABA, glutamate, and norepinephrine. We discuss our current understanding of the neural circuitry through which these neurotransmitters regulate CRH cell activity, as well as the plastic changes in this circuitry induced by acute and chronic stress and the resultant changes in HPA function.

Overnight ACTH-cortisol dose responsiveness: comparison with 24-h data, metyrapone administration and insulin-tolerance test in healthy adults

OBJECTIVE

To estimate the dose dependence of endogenous ACTH stimulation of adrenal cortisol secretion overnight.

DESIGN

Ten-minute sampling for ACTH and cortisol over 8 and 24 h (n = 17), after metyrapone administration (n = 6), during an insulin-tolerance test (n = 7).

SUBJECTS

Healthy adults.

MEASUREMENTS

ACTH dose-responsive estimates.

RESULTS

Twenty-four hour ACTH-cortisol concentration pairs yielded an estimated EC(50) (one-half maximally stimulatory ACTH concentration) of 5·1 (2·2-9·5) pmol/l [median (range)]. This did not differ from EC(50) s based on 8- or 6-h data [5·9 (3·5-11) and 7·5 (3·7-41) pmol/l] in the same individuals. ACTH efficacy (maximally stimulatable cortisol secretion rate) was 8·4 (3·1-20), 11 (5·9-24) and 15 (5·9-22) nmol/l/min, when calculated over 24, 8 and 6 h, respectively (P = NS). Adrenal sensitivity (slope term) was also consistent across sampling durations, viz. 14 (1·3-95), 18 (1·3-64) and 20 (1·3-64) slope units. Compared with placebo, metyrapone reduced ACTH efficacy from 11 (6·2-62) to 2·8 (1·5-4·5) nmol/l/min for cortisol (n = 9, P < 0·001), while increasing ACTH efficacy for 11-desoxycortisol from 2·3 (0·9-2·9) to 99 (70-218) nmol/l/min (n = 6, P < 0·01), thus affirming face validity. Combined ACTH and cortisol responses to hypoglycaemia allowed an estimate of ACTH efficacy of 28 (22-81) nmol/l/min, compared with the control value of 8·7 (5·6-26), suggesting enhanced adrenal responsiveness.

CONCLUSIONS

The results suggest that endogenous ACTH-adrenal drive can be approximated from overnight 8-h sampling of paired ACTH and cortisol concentrations. This strategy may have merit in clinical research in childhood, pregnancy, anxiety states and frail elderly individuals, when ACTH injections are not desired.

Tripartite control of dynamic ACTH-cortisol dose responsiveness by age, body mass index, and gender in 111 healthy adults

BACKGROUND

Recent analyses in small cohorts suggest that pituitary hormones exert time-varying (viz., initial and delayed) dynamic dose-responsive effects on target glands, wherein down-regulating dynamics are inferable on a time scale of single pulses.

HYPOTHESIS

Age, body mass index (BMI), and sex modulate the rapid potency-down-regulating dynamics of pulsatile pituitary ACTH-adrenal cortisol coupling overnight.

LOCATION

The study was conducted at a clinical translational research unit.

SUBJECTS

Subjects included healthy adults (48 women, 63 men; aged 18-77 yr; BMI 18-42 kg/m(2)).

OUTCOMES

Outcomes included analytical dose-response estimates of endogenous ACTH efficacy, dynamic ACTH potency, and adrenal sensitivity from overnight 10-min ACTH-cortisol profiles.

RESULTS

Stepwise backward-elimination, multivariate-regression analysis revealed that in the combined cohorts (n = 111), age was associated with enhanced initial ACTH potency (R = 0.265, P = 0.005). Moreover, age and BMI jointly attenuated adrenal sensitivity (R = 0.334, P = 0.0017) and augmented down-regulated ACTH potency (R = 0.321 and P = 0.0028). Exploratory gender-segmented analyses showed that these outcomes might be explained by: (1) a negative effect of age in men on adrenal sensitivity (R = 0.270, P = 0.034) and (2) positive effects of age in men (R = 0.332, P = 0.0019) and BMI in women (R = 0.331, P = 0.024) on initial ACTH potency.

CONCLUSIONS

In healthy adults, adrenal sensitivity to endogenous ACTH pulses, ACTH efficacy, and ACTH potency is associated with age, BMI, and gender. These findings may explain conflicting data in earlier literature and introduce the need to control all three of age, BMI, and sex in future studies of the stress-adaptive axis.

Comparison of pituitary-adrenal responsiveness between insulin tolerance test and growth hormone-releasing peptide-2 test: a pilot study

Insulin tolerance test (ITT) is the gold standard for assessing the hypothalamic-pituitary-adrenal (HPA) function. GH-releasing peptide (GHRP)-2, which has a strong GH-stimulating activity, is useful for diagnosing GH deficiency as well as ITT. Additionally, GHRP-2 is also known to activate HPA axis. There have been no comparative studies of pituitary-adrenal responsiveness between GHRP-2 test and ITT in patients with hypothalamic/pituitary disease. To assess whether GHRP-2 test could be an alternative to ITT for diagnosing HPA axis failure, both ITT and GHRP-2 test were performed in 15 patients suspected of hypopituitarism. A 100mug dose of GHRP-2 was administered intravenously and plasma ACTH and serum cortisol concentrations were measured. In ITT, a peak cortisol value over 18mug/dl is considered normal. Nine patients were diagnosed as HPA axis failure by ITT. Their median peak cortisol in GHRP-2 test was 11.4mug/ml. In 6 patients diagnosed as normal HPA axis status by ITT, their median peak cortisol in response to GHRP-2 test was 21.4mug/dl, significantly higher (p=0.0032) than seen in patients diagnosed as HPA axis failure. There was a strong correlation between the peak cortisol in GHRP-2 test and ITT (r=0.817; p<0.0001). When the cut-off value for the peak cortisol in GHRP-2 test was set to 13-14mug/dl for diagnosing HPA axis failure, the specificity and sensitivity were 100% and 88.9%, respectively. Although further studies that include normal subjects are needed, these preliminary results suggest the possibility that GHRP-2 test may be an alternative to ITT for assessing HPA axis function.

Diagnosis of secondary adrenal insufficiency in patients with hypothalamic-pituitary disease: comparison between serum and salivary cortisol during the high-dose short synacthen test

OBJECTIVE

Accurate assessment of adrenal function is essential in patients with hypothalamic-pituitary-adrenal (HPA) disease. The measurement of salivary cortisol (SaC) instead of serum cortisol (SeC) offers several advantages, such as the determination of the free hormone. We evaluated the diagnostic value of SeC and SaC both unstimulated and during a high-dose short synacthen test (HDT) in comparison to the insulin tolerance test (ITT).

DESIGN

Comparative study between 2005 and 2007.

METHODS

Fifty-five patients with HPA impairment and 21 healthy controls were enrolled. Samples were collected in the early morning and over 120 min during the HDT. Receiver operating characteristic analysis revealed individual thresholds for four HDT periods (0-30, 0-60, 0-90, and 0-120 min).

RESULTS

The ITT identified 30 subjects as adrenal insufficient. With respect to the four HDT periods, sensitivity and specificity were 67-79% and 71-88% for SeC, compared with 63-72% and 72-86% for SaC. If upper and lower thresholds (with specificities >95%) were applied, patients were diagnosed in 40-45% by SeC and in 25-31% by SaC. The combination of basal cortisol and HDT allowed a diagnosis in 47-49% (SeC) and in 42-45% (SaC) respectively.

CONCLUSION

We suggest the determination of basal SeC or SaC as first-line test. In comparison to the ITT, the HDT has only limited value in screening for alterations of the HPA axis. If the HDT is performed, sampling may be limited to 30 min post-synacthen, using either SeC or SaC. Due to the ease of collection and the independence of binding proteins, SaC may be preferable.

Clinical insights into the safety and utility of the insulin tolerance test (ITT) in the assessment of the hypothalamo-pituitary-adrenal axis

OBJECTIVE

The insulin tolerance test (ITT) is the gold standard for assessing GH and cortisol production in pituitary disease. However, areas of uncertainty remain regarding its safety in older people, the optimal duration of the test and its performance in insulin resistant states. Whether basal cortisol concentration can reliably predict an adequate adrenal response to hypoglycaemia remains to be determined.

PATIENTS AND DESIGN

We performed a cross-sectional retrospective examination of 197 consecutive patients (mean age 41.8 +/- 16.4, range 13-76 years) with pituitary disease who underwent the ITT over 18 months. The standard intravenous insulin dose administered was 0.15 units/kg body weight. Patients with acromegaly or with type 2 diabetes received 0.2 units/kg; those with basal cortisol < 100 nmol/l received 0.1 units/kg.

RESULTS

Adequate hypoglycaemia (nadir glucose < 2.2 mmol/l) was achieved in 87% of patients, amongst whom 17% did not achieve peak cortisol until 120 min. There were no significant adverse events, even in those >or= 65 years. Of the 18 patients who had basal cortisol < 100 nmol/l, 78% achieved adequate hypoglycaemia; 29% of those had an adequate peak cortisol response >or= 500 nmol/l. A receiver operating characteristics curve identified a basal cortisol of >or= 393 nmol/l to predict a normal peak cortisol response to hypoglycaemia.

CONCLUSIONS

In specialized units, the ITT is safe even in elderly patients and those with hypocortisolaemia. The standard 90-min. cut-off for the ITT misses one in six peak cortisol responses. Some patients with basal cortisol < 100 nmol/l had a normal cortisol response to hypoglycaemia.

Hypopituitarism: clinical features, diagnosis, and management

Hypopituitarism is characterized by loss of function of the anterior pituitary gland. It is a rare condition that can present at any age and is caused by pathology of the hypothalamic-pituitary axis or one of many gene mutations. The symptoms and signs of hypopituitarism may evolve over several years and be nonspecific or related to the effects of the underlying disease process or to hormone deficiencies. Investigation of patients requires a combination of basal hormone levels and dynamic function tests; management requires regular monitoring. The goal of physicians managing patients who have hypopituitarism is to improve their health and long-term outcome.

Parabolic flight experience is related to increased release of stress hormones

Numerous studies have shown significant effects of weightlessness on adaptational processes of the CNS, cardiovascular and/or muscular system. Most of these studies have been carried out during parabolic flights, using the recurring 20 s of weightlessness at each parabola. Although some of these studies reported on potential influences not only of weightlessness but also of the stressful situation within a parabolic flight, especially provoked by the ongoing changes between 1.8, 1 and 0 G, so far there seems to be only marginal information about objective parameters of stress evoked by parabolic flights. By collecting blood samples from a permanent venous catheter several times during parabolic flights, we were able to show an increase of prolactin, cortisol and ACTH in the course of a 120 min flight. We conclude, therefore, that previous reported effects of weightlessness on adaptational processes may be affected not only by weightlessness but also by the exposure to other stressors experienced within the environment of a Zero-G airbus.

Hormonal, pituitary magnetic resonance, LHX4 and HESX1 evaluation in patients with hypopituitarism and ectopic posterior pituitary lobe

OBJECTIVE

LHX4 and HESX1 are important in early stages of pituitary development and their mutations can be associated with an ectopic posterior lobe (EPL) in the pituitary of patients with hypopituitarism. The EPL can be located at the median eminence or at the path of the pituitary stalk. The aim of this study was to analyse LHX4 and HESX1 and characterize the hormonal deficiency profiles, establishing relationships with magnetic resonance imaging (MRI) findings in these patients.

PATIENTS AND DESIGN

Sixty-two patients with hypopituitarism associated with EPL were submitted to evaluation of pituitary function, analysis of MRI with EPL location and molecular analysis of LHX4 and HESX1 using polymerase chain reaction (PCR), digestion with restriction enzyme and automatic sequencing.

RESULTS

Forty-two patients had a nonvisualized pituitary stalk (NPS), and 20 a visualized pituitary stalk (VPS). Most patients (95%) with NPS had combined pituitary hormone deficiency (CPHD), with ACTH deficiency in 85%. In patients with VPS, CPHD was found in 50% and ACTH deficiency occurred in only 20%. The frequency of the location of EPL was similar in patients with VPS and NPS: 35% at median eminence and 65% at the path of the stalk. No mutations in LHX4 and HESX1 were identified. Three new polymorphisms in LHX4 were found.

CONCLUSIONS

ACTH deficiency is frequent in patients with hypopituitarism and NPS (85%), the location of EPL at the median eminence was not predictive of the hormonal profile [isolated GH deficiency (IGHD) or CPHD], and LHX4 and HESX1 genes mutations remain rare causes of hypopituitarism associated with EPL.

Brief review and commentary: diagnosis of pediatric pituitary disorders

Pediatric pituitary diagnosis is complicated by the unique developmental characteristics, secretory patterns and regulation of each pituitary hormone system. Although dynamic test procedures have been described, validation of each procedure is limited and universally agreed diagnostic criteria are not available. Clinical acumen, experience and judgment continue to be primary elements of pituitary diagnosis.

Low-dose glucose infusion after achieving critical hypoglycemia during insulin tolerance testing: effects on time of hypoglycemia, neuroendocrine stress response and patient's discomfort in a pilot study

OBJECTIVE

The insulin tolerance test (ITT) is regarded as the gold standard for the evaluation of pituitary ACTH and growth hormone reserve. However, the intended critical hypoglycemia results in considerable discomfort and requires close surveillance during the test.

DESIGN AND METHODS

In a pilot study, we evaluated whether the ITT could be markedly simplified, made less hazardous and more convenient by routine i.v. low-dose glucose administration after hypoglycemia has been achieved. Sixteen healthy subjects (three females, 13 males) were tested twice in a randomized, single-blinded fashion, receiving 0.15 IU insulin/kg body weight as an i.v. bolus. After hypoglycemia (serum glucose less than 2.2 mmol/l) had been achieved, 500 ml isotonic saline (protocol A (A)), or 500 ml 5% glucose solution (protocol B (B)) were infused over 30 min.

RESULTS

Compared with saline, glucose infusion shortened the period of hypoglycemia from 31 + 14 to 17 + 6 min (P < 0.01). In addition, prolonged duration of hypoglycemia (>45 min) was reduced (6 subjects in protocol A vs none in protocol B). Despite shorter duration of hypoglycemia, all subjects had adequate stimulated cortisol (>500 nmol/l) and hGH (>5 microg/l) levels. Mean peak concentrations of plasma ACTH (24 +/- 12 pmol/l (A) vs 21 +/- 8 pmol/l (B)), serum cortisol (690 +/- 83 nmol/l vs 634 +/- 83 nmol/l) and serum hGH (26 +/- 16 microg/l vs 22 +/- 13 microg/l) were slightly, but not significantly lower. In contrast, glucose infusion significantly reduced peak plasma epinephrine levels at 45 min (4.96 +/- 4.91 pmol/l (A) vs 1.53 +/- 1.1 pmol/l (B), P < 0.05) and ameliorated discomfort, as evaluated by a visual analog scale (P < 0.05).

CONCLUSIONS

Taken together, our pilot study suggests that, while the duration of hypoglycemia is shortened and acute epinephrine response is reduced, low-dose infusion of glucose does not significantly alter peak cortisol and growth hormone responses during ITT. Studies with a larger number of subjects and patients with suspected hypopituitarism are needed to further evaluate this modified protocol.

Diagnosis and treatment of hypopituitarism: an update

Diagnosis and treatment of patients with hypopituitarism needs careful clinical evaluation and individual optimization. Symptoms of hypopituitarism are variable, often insidious in onset and dependent on the degree of hormone deficiency. Diagnosis of hypopituitarism can be straightforward by measuring reduced basal hormone levels. Frequently, dynamic stimulation tests are indicated in equivocal basal hormone levels or to diagnose partial hormone deficiencies. Knowledge of the use and limitations of these dynamic tests is mandatory for proper interpretation. Hormone replacement therapy should be individualized, taking into account possible interactions. Persisting symptoms and reduced quality of life are frequently reported, explained by, at least in part, intrinsic imperfections of hormone replacement strategies in mimicking normal hormone secretion. In the present overview, the principles of diagnosis and treatment of hypopituitarism are discussed.

Adrenal insufficiency

Adrenal insufficiency is caused by either primary adrenal failure (mostly due to autoimmune adrenalitis) or by hypothalamic-pituitary impairment of the corticotropic axis (predominantly due to pituitary disease). It is a rare disease, but is life threatening when overlooked. Main presenting symptoms such as fatigue, anorexia, and weight loss are non-specific, thus diagnosis is often delayed. The diagnostic work-up is well established but some pitfalls remain, particularly in the identification of secondary adrenal insufficiency. Despite optimised life-saving glucocorticoid-replacement and mineralocorticoid-replacement therapy, health-related quality of life in adrenal insufficiency is more severely impaired than previously thought. Dehydroepiandrosterone-replacement therapy has been introduced that could help to restore quality of life. Monitoring of glucocorticoid-replacement quality is hampered by lack of objective methods of assessment, and is therefore largely based on clinical grounds. Thus, long-term management of patients with adrenal insufficiency remains a challenge, requiring an experienced specialist. However, all doctors should know how to diagnose and manage suspected acute adrenal failure.

Hypothalamo-pituitary-adrenal axis integrity after cranial irradiation for childhood posterior fossa tumours

BACKGROUND

The evolution of anterior pituitary deficits after treatment for pituitary tumours has been largely attributed to local irradiation, but may be influenced as much by tumour mass or surgery. Other than growth hormone (GH) insufficiency, the late endocrinopathies after survival from non-central brain tumours have been little documented. The aim of this study was to investigate the hypothalamic-pituitary-adrenal (HPA) axis in long-term survivors of cranial irradiation for childhood posterior fossa tumours.

PROCEDURE

We studied long-term data in patients treated prepubertally for posterior fossa brain tumours and systematically referred by radiation oncologists for growth and pubertal monitoring to the London Centre for Paediatric Endocrinology over the last 25 years. They must have undergone HPA axis assessment twice, first prepubertally at documentation of growth failure, and second at completion of growth and puberty. Data on sixteen patients (12 males, 4 females; median age: 5.7 years, range: 2.5-8.8 years), who had undergone excision surgery with high dose cranial irradiation and/or chemotherapy for childhood posterior fossa tumours, were examined. Patients were followed for a median of 11.0 (range: 6.8-21.4) years after radiotherapy. HPA axis assessment was undertaken with the insulin-induced hypoglycaemia test (ITT). Basal thyroid, cortisol and gonadal function tests were undertaken annually throughout the follow-up period and any deficits replaced.

RESULTS

At each ITT, all patients mounted an inadequate GH response. By the end of the follow-up period all patients remained severely GH deficient, two (12.5%) had partial ACTH insufficiency, one (6.3%) had secondary hypothyroidism but none were gonadotropin deficient or hyperprolactinaemic.

CONCLUSIONS

Unlike the severe, evolving multiple pituitary deficits after treatment of pituitary or central tumours in adults, these findings in children with posterior fossa tumours suggest that, with the exception of GH, neurotoxicity due to irradiation per se is associated with a low prevalence of anterior pituitary hormone deficiencies, even at a long follow-up. Since the children in this study were selected for assessment on the basis of growth failure, the high prevalence of GH insufficiency at first testing is to be expected; however, the early onset (within 1-3 years of irradiation) and permanence we have identified supports the view that GH is the most sensitive hormone to radiation injury.