A novel variant of growth hormone (GH) insufficiency following low dose cranial irradiation

Long-term and late treatment consequences: endocrine and metabolic effects

PURPOSE OF REVIEW

Cancer therapies often result in the 'late effect of cancer treatment' whereby secondary health complications emerge years after radiotherapy and chemotherapy. This review focuses on endocrine and metabolic consequences in adult cancer survivors as late treatment effects.

RECENT FINDINGS

Endocrine and metabolic disorders are among the most common late effects. Endocrine disorders include hypopituitarism, which leads to growth hormone deficiency, hypogonadism, adrenal insufficiency and hypothyroidism and related clinical manifestations. Hypogonadism in particular is associated with a wide range of health complications requiring input from the like of endocrine and fertility specialists. Immune checkpoint inhibitors are novel anticancer agents, some of which are uniquely associated with hypophysitis which requires early recognition and management, including steroid replacement. Metabolic syndrome, a significant risk for cardiovascular disease, is highly prevalent. Although the effects of cranial irradiation on the hypothalamic-pituitary system are more apparent, the relationship between chemotherapy and endocrine/metabolic disorders remains to be elucidated. There exist published guidelines for monitoring endocrine and cardiometabolic risk in cancer survivors, but the extent of monitoring appears insufficient.

SUMMARY

Regular monitoring and early management of endocrine/metabolic disorders is required to prevent the elevated rates of health complications after cancer treatment, and thereby improve cancer survivorship.

Effect of cancer treatment on hypothalamic-pituitary function

The past 30 years have seen a great improvement in survival of children and young adults treated for cancer. Cancer treatment can put patients at risk of health problems that can develop many years later, most commonly affecting the endocrine system. Patients treated with cranial radiotherapy often develop dysfunction of the hypothalamic-pituitary axis. A characteristic pattern of hormone deficiencies develops over several years. Growth hormone is disrupted most often, followed by gonadal, adrenal, and thyroid hormones, leading to abnormal growth and puberty in children, and affecting general wellbeing and fertility in adults. The severity and rate of development of hypopituitarism is determined by the dose of radiotherapy delivered to the hypothalamic-pituitary axis. Individual growth hormone deficiencies can develop after a dose as low as 10 Gy, whereas multiple hormone deficiencies are common after 60 Gy. New techniques in radiotherapy aim to reduce the effect on the hypothalamic-pituitary axis by minimising the dose received. Patients taking cytotoxic drugs do not often develop overt hypopituitarism, although the effect of radiotherapy might be enhanced. The exception is adrenal insufficiency caused by glucocorticosteroids which, although transient, can be life-threatening. New biological drugs to treat cancer can cause autoimmune hypophysitis and hypopituitarism; therefore, oncologists and endocrinologists should be vigilant and work together to optimise patient outcomes.

Radiation-induced hypopituitarism

PURPOSE OF REVIEW

Progressive and irreversible neuro-endocrine dysfunction following radiation-induced damage to the hypothalamic-pituitary (h-p) axis is the most common complication in cancer survivors with a history of cranial radiotherapy involving the h-p axis and in patients with a history of conventional or stereotactic pituitary radiotherapy for pituitary tumours. This review examines the controversy about the site and pathophysiology of radiation damage while providing an epidemiological perspective on the frequency and pattern of radiation-induced hypopituitarism.

RECENT FINDINGS

Contrary to the previously held belief that h-p axis irradiation with doses less than 40 Gy result in a predominant hypothalamic damage with time-dependent secondary pituitary atrophy, recent evidence in survivors of nonpituitary brain tumours suggests that cranial radiation causes direct pituitary damage with compensatory increase in hypothalamic release activity. Sparing the hypothalamus from significant irradiation with sterteotactic radiotherapy for pituitary tumours does not appear to reduce the long-term risk of hypopituitarism.

SUMMARY

Radiation-induced h-p dysfunction may occur in up to 80% of patients followed long term and is often associated with an adverse impact on growth, body image, skeletal health, fertility, sexual function and physical and psychological health. A detailed understanding of pathophysiological and epidemiological aspects of radiation-induced h-p axis dysfunction is important to provide targeted and reliable long-term surveillance to those at risk so that timely diagnosis and hormone-replacement therapy can be provided.

ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context

This report provides a review of early and late effects of radiation in normal tissues and organs with respect to radiation protection. It was instigated following a recommendation in Publication 103 (ICRP, 2007), and it provides updated estimates of 'practical' threshold doses for tissue injury defined at the level of 1% incidence. Estimates are given for morbidity and mortality endpoints in all organ systems following acute, fractionated, or chronic exposure. The organ systems comprise the haematopoietic, immune, reproductive, circulatory, respiratory, musculoskeletal, endocrine, and nervous systems; the digestive and urinary tracts; the skin; and the eye. Particular attention is paid to circulatory disease and cataracts because of recent evidence of higher incidences of injury than expected after lower doses; hence, threshold doses appear to be lower than previously considered. This is largely because of the increasing incidences with increasing times after exposure. In the context of protection, it is the threshold doses for very long follow-up times that are the most relevant for workers and the public; for example, the atomic bomb survivors with 40-50years of follow-up. Radiotherapy data generally apply for shorter follow-up times because of competing causes of death in cancer patients, and hence the risks of radiation-induced circulatory disease at those earlier times are lower. A variety of biological response modifiers have been used to help reduce late reactions in many tissues. These include antioxidants, radical scavengers, inhibitors of apoptosis, anti-inflammatory drugs, angiotensin-converting enzyme inhibitors, growth factors, and cytokines. In many cases, these give dose modification factors of 1.1-1.2, and in a few cases 1.5-2, indicating the potential for increasing threshold doses in known exposure cases. In contrast, there are agents that enhance radiation responses, notably other cytotoxic agents such as antimetabolites, alkylating agents, anti-angiogenic drugs, and antibiotics, as well as genetic and comorbidity factors. Most tissues show a sparing effect of dose fractionation, so that total doses for a given endpoint are higher if the dose is fractionated rather than when given as a single dose. However, for reactions manifesting very late after low total doses, particularly for cataracts and circulatory disease, it appears that the rate of dose delivery does not modify the low incidence. This implies that the injury in these cases and at these low dose levels is caused by single-hit irreparable-type events. For these two tissues, a threshold dose of 0.5Gy is proposed herein for practical purposes, irrespective of the rate of dose delivery, and future studies may elucidate this judgement further.

Hypopituitarism following radiotherapy

Deficiencies in anterior pituitary hormones secretion ranging from subtle to complete occur following radiation damage to the hypothalamic-pituitary (h-p) axis, the severity and frequency of which correlate with the total radiation dose delivered to the h-p axis and the length of follow up. Selective radiosensitivity of the neuroendocrine axes, with the GH axis being the most vulnerable, accounts for the high frequency of GH deficiency, which usually occurs in isolation following irradiation of the h-p axis with doses less than 30 Gy. With higher radiation doses (30-50 Gy), however, the frequency of GH insufficiency substantially increases and can be as high as 50-100%. Compensatory hyperstimulation of a partially damaged h-p axis may restore normality of spontaneous GH secretion in the context of reduced but normal stimulated responses; at its extreme, endogenous hyperstimulation may limit further stimulation by insulin-induced hypoglycaemia resulting in subnormal GH responses despite normality of spontaneous GH secretion in adults. In children, failure of the hyperstimulated partially damaged h-p axis to meet the increased demands for GH during growth and puberty may explain what has previously been described as radiation-induced GH neurosecretory dysfunction and, unlike in adults, the ITT remains the gold standard for assessing h-p functional reserve. Thyroid-stimulating hormone (TSH) and ACTH deficiency occur after intensive irradiation only (>50 Gy) with a long-term cumulative frequency of 3-6%. Abnormalities in gonadotrophin secretion are dose-dependent; precocious puberty can occur after radiation dose less than 30 Gy in girls only, and in both sexes equally with a radiation dose of 30-50 Gy. Gonadotrophin deficiency occurs infrequently and is usually a long-term complication following a minimum radiation dose of 30 Gy. Hyperprolactinemia, due to hypothalamic damage leading to reduced dopamine release, has been described in both sexes and all ages but is mostly seen in young women after intensive irradiation and is usually subclinical. A much higher incidence of gonadotrophin, ACTH and TSH deficiencies (30-60% after 10 years) occur after more intensive irradiation (>60 Gy) used for nasopharyngeal carcinomas and tumors of the skull base, and following conventional irradiation (30-50 Gy) for pituitary tumors. The frequency of hypopituitarism following stereotactic radiotherapy for pituitary tumors is mostly seen after long-term follow up and is similar to that following conventional irradiation. Radiation-induced anterior pituitary hormone deficiencies are irreversible and progressive. Regular testing is mandatory to ensure timely diagnosis and early hormone replacement therapy.

Cranial irradiation and growth hormone neurosecretory dysfunction: a critical appraisal

CONTEXT

It has been suggested that radiation-induced GH neurosecretory dysfunction exists in children; however, the pathophysiology is poorly understood, and it is unknown if such a phenomenon exists in adult life.

STUDY SUBJECTS

Twenty-four-hour spontaneous GH secretion was studied by 20-min sampling both in the fed state (n = 16; six women) and the last 24 h of 33-h fast (n = 10; three women) in adult cancer survivors of normal GH status defined by two GH provocative tests, 13.1 +/- 1.6 (range, 3-28) yr after cranial irradiation (18-40 Gy) for nonpituitary brain tumors (n = 12) or leukemia (n = 4) in comparison with 30 (nine women) age- and body mass index-matched normal controls (fasting, 11 men and three women).

RESULTS

Using previously published diagnostic thresholds, all patients had stimulated peak GH responses in the normal range to both the insulin tolerance test and the combined GHRH plus arginine stimulation test, as well as normal individual mean profile GH levels during the fed and fasting states. However, gender-specific comparisons revealed marked reduction (by 40%) in the overall peak GH responses to both provocative tests but similar GH secretory profiles; no differences were seen in the pulsatile attributes of GH secretion (cluster analysis) or the profile absolute and mean GH levels in the fed state or when the hypothalamic-pituitary axis was stimulated by fasting.

CONCLUSIONS

Radiation-induced GH neurosecretory dysfunction either does not exist or is a very rare phenomenon in irradiated adult cancer survivors. The normality of physiological GH secretion in the context of reduced maximum somatotroph reserve suggests compensatory overdrive of the partially damaged somatotroph axis and constitutes a relative argument against somatotroph dysfunction being explained purely by hypothalamic damage with secondary atrophy due to GHRH deficiency. It is therefore possible that radiation in doses less than 40 Gy causes dual damage to both the pituitary and the hypothalamus.

Pathophysiology of radiation-induced growth hormone deficiency: efficacy and safety of GH replacement

Radiation-induced growth hormone deficiency (GHD) is primarily due to hypothalamic damage. GH secretion by the pituitary may be affected either secondary to some degree of quantitative deprivation of hypothalamic input or, if the radiation dose is high enough, by direct pituitary damage. As a consequence, the neurosecretory profile of GH secretion in an irradiated patient remains pulsatile and qualitatively intact. The frequency of pulse generation is unaffected, but the amplitude of the GH pulses is markedly reduced. Over the last 25 years, the final heights achieved by children receiving GH replacement for radiation-induced GHD have improved; these improvements are attributable to refinements in GH dosing schedules, increased use of GnRH analogues for radiation-induced precocious puberty, and a reduced time interval between completion of irradiation and initiation of GH therapy. When retested at the completion of growth, 80-90% of these teenagers are likely to prove severely GH deficient and, therefore, will potentially benefit from GH replacement in adult life. Such long-term GH treatment in patients treated previously for a brain tumor means that critical and continuous surveillance must be devoted to the risk of tumor recurrence and the possibility of second neoplasms.

Reduction of adult height in childhood acute lymphoblastic leukemia survivors after prophylactic cranial irradiation

BACKGROUND

Impaired linear growth is a well-recognized complication in long-term childhood ALL survivors who received cranial irradiation. However, as many patients achieve a final height between the 5th and the 95th centile, the true incidence of linear growth impairment might be underestimated.

METHODS

Reduction of adult height (RAH) was estimated in adult childhood ALL survivors with and without cranial irradiation. RAH was calculated as the difference between target height (TH) and final height (FH). TH was calculated according to the formula TH = {[(height father + height mother +/- 12)/2] + 3}. RAH was assessed in 79 adult childhood ALL survivors in first complete remission who had received cranial irradiation 25 Gy (Group I, n = 53), 18 Gy (Group II, n = 10) or chemotherapy alone (controls, n = 16).

RESULTS

RAH was 8.6 +/- 8.2 cm in Group I (P = 0.001 vs. controls), 6.2 +/- 3.2 cm in Group II (P = 0.01 vs. controls), and 1.7 +/- 4.6 in controls (chemotherapy only). There was no significant difference between Group I and Group II. In Group I females had more RAH than males (P = 0.02). RAH was related to younger age at diagnosis (P = 0.001).

CONCLUSIONS

The deficit between target height and final height highlights the reduction of adult height in the majority of male and female childhood ALL survivors who had received prophylactic cranial irradiation, in particular in those who were diagnosed at a younger age. This reduction would have been masked if patients FH was only compared with standard methods. RAH might be a sensitive predictor for growth hormone deficiency as these results suggest that radiation-induced growth hormone deficiency in these patients is the rule rather than the exception.

Hypopituitarism as a consequence of brain tumours and radiotherapy

Radiation-induced damage to the hypothalamic-pituitary (h-p) axis is associated with a wide spectrum of subtle and frank abnormalities in anterior pituitary hormones secretion. The frequency, rapidity of onset and the severity of these abnormalities correlate with the total radiation dose delivered to the h-p axis, as well as the fraction size, younger age at irradiation, prior pituitary compromise by tumour and/or surgery and the length of follow up. Whilst, the hypothalamus is the primary site of radiation-induced damage, secondary pituitary atrophy evolves with time due to impaired secretion of hypothalamic trophic factors and/or time-dependent direct radiation-induced damage. Selective radiosensitivity in the neuroendocrine axes with the GH axis being the most vulnerable to radiation damage accounts for the high frequency of GH deficiency, which usually occurs in isolation following irradiation of the h-p axis with doses less than 30 Gy. With higher radiation doses (30-50 Gy), however, the frequency of GH insufficiency substantially increases and can be as high as 50-100%, and TSH and ACTH deficiency start to occur with a long-term cumulative frequency of 3-6%. Abnormalities in gonadotrophin secretion are dose-dependent; precocious puberty can occur after radiation dose less than 30 Gy in girls only, and in both sexes equally with a radiation dose of 30-50 Gy. Gonadotrophin deficiency occurs infrequently and is usually a long-term complication following a minimum radiation dose of 30 Gy. Hyperprolactinemia, due to hypothalamic damage leading to reduced dopamine release, has been described in both sexes and all ages but is mostly seen in young women after intensive irradiation and is usually subclinical. A much higher incidence of gonadotrophin, ACTH and TSH deficiencies (30-60% after 10 years) occur after more intensive irradiation (>70 Gy) used for nasopharyngeal carcinomas and tumours of the skull base and following conventional irradiation (30-50 Gy) for pituitary tumours. Radiation-induced anterior pituitary hormone deficiencies are irreversible and progressive. Regular testing is mandatory to ensure timely diagnosis and early hormone replacement therapy to improve linear growth and prevent short stature in children cured from cancer, and in adults preserve sexual function, prevent ill health and osteoporosis and improve the quality of life.

Spectral pattern complexity analysis and the quantification of voice normality in healthy and radiotherapy patient groups

Vocal fold functionality may alter in response to direct radiotherapy or indirectly by perturbation of the hypothalamic-pituitary axis. Perceptual assessment of voice quality is difficult to summarise in a single, reliable figure of normality and normality itself is undefined. In this study spectral analysis of vocal fold vibration, based on impedance variations measured across the larynx using an electro-glottogram, is used to build a single parameter description of standard vowel phonation in the normal male population. Patient data and perceptual assessment are then compared to this standard. The spectral pattern of the vowel/i/ electro-glottogram time series is analysed using approximate entropy after dynamic fundamental-harmonic frequency normalisation. The approximate entropy provides a single estimate of the spectral pattern complexity. A cohort of 89 normal males formed two statistically distinct groups, G1, with strong spectral pattern and high complexity 0.338 (+/-0.036), and G2 with a weak spectral pattern and low complexity 0.175 (+/-0.049). Membership ratio G1:G2 was 2:1. A cohort of 30 male larynx cancer cases were analysed approximately 3-6 months after irradiation, and three male prophylactic cranial irradiation cases some years after treatment. Two-thirds of patients had G2 or lower levels of complexity. The lower G2 complexity level appears to be the subjective, as well as the objective, threshold for voice normality.

Children, cancer, and nutrition--A dynamic triangle in review

The overall cure rate for cancer in childhood now exceeds 70% and is projected to reach 85% by the year 2010 in industrialized countries. Therefore, major attention is being placed on reducing the side effects of therapy. However, 85% of the world's children live in developing countries, where access to adequate care often is limited and health status frequently is influenced adversely by prevalent infectious diseases and malnutrition. Despite several confounding factors (different definitions of nutritional status, the wide variety of measures used for its assessment, the selection biases by disease and stage, treatment protocols of variable dose intensity and efficacy, small sample sizes of the studies conducted in the last 20 years), it is accepted that the prevalence of malnutrition at diagnosis averages 50% in children with cancer in developing countries; whereas, in industrialized countries, it is related to the type of tumor and the extent of the disease, ranging from < 10% in patients with standard-risk acute lymphoblastic leukemia to 50% in patients with advanced neuroblastoma. The importance of nutritional status in children with cancer is related to its possible influence on the course of the disease and survival. Some authors have described decreased tolerance of chemotherapy associated with altered metabolism of antineoplastic drugs, increased infection rates, and poor clinical outcome in malnourished children. In this article, the authors review methods of nutritional assessment and the pathogenesis of nutritional morbidity in children with cancer as well as correlations of nutritional status with diagnosis, treatment, and outcome.

Growth following malignancy

Disturbed growth in the child surviving cancer is multifactorial. This chapter examines the evidence for, and the difficulties in determining, individual drug treatment or disease effects at multiple endocrine levels influencing growth and against a changing baseline of adjuvant cancer therapies with potentially additive toxicity. The evolutionary pattern and potential aetiology of the neuro-endocrine deficit and growth-plate disturbance, the (unrandomized) effects of hormone replacement therapy and areas which require further study are also addressed. The reasons why growth hormone (GH) secretion is so exquisitely sensitive to disturbance, even though deficiencies soon after lesser cranial insults can be difficult to detect, are explored with evidence cited from the few existing prospective and interventional studies. The extent and nature of the hypothalamo-pituitary disturbance needs further prospective interventional study and disease-site- and treatment-specific comparisons. Practical treatment and surveillance strategies to optimize growth potential, age-appropriate development, peak bone mineral accretion, hair re-growth and future health and well-being are also suggested. Health-related outcomes resulting from today's newer therapies and enhanced surveillance need documenting in future (inter)national cancer trials, where randomized studies of hormonal intervention may also become possible.

Body composition of long-term survivors of acute lymphoblastic leukaemia

BACKGROUND

Long-term quality of life is of growing importance in children previously treated for malignancy. Obesity defined indirectly from indices of height and weight, has been described in long-term survivors of acute lymphoblastic leukaemia (ALL) and hypothesised to be a consequence of previous cranial irradiation.

PROCEDURE

In this study, measures of whole and regional body composition using skinfold and dual energy X-ray absorptiometry (DEXA) measurements have been made in 35 long-term survivors of ALL who had received cranial irradiation and chemotherapy. To assess the influence of cranial irradiation, results were compared with those obtained in 21 children treated for other malignancies, who received chemotherapy alone and with 31 healthy sibling controls.

RESULTS

Girls treated for ALL were significantly fatter than those treated for other malignancies or healthy control siblings whether measured by skinfold thickness (median (range) 37.4% (17.9-41.3) vs. 24.6% (19.1-35.0) and 28.8% (19.6-43.1), respectively, P<0.01) or DEXA (33.5% (20.5-42.8) vs. 25.5% (16.5-31.0) and 24.5% (18.8-53.6), respectively, P<0.01). Boys treated for ALL were not significantly fatter than boys in the other two groups. Measures of whole body percent fat derived from DEXA were persistently less than those derived from skinfold measurements with a mean (95% CI) difference of 2.4% (1.7-3.1, P<0.001) for all groups combined. In ALL survivors, using regression equations for skinfold thicknesses derived from controls with DEXA as the 'gold standard' method, fat mass was significantly overestimated.

CONCLUSION

Female survivors of ALL are significantly fatter than those of other malignancies and healthy sibling controls. Caution should be observed in the application of published equations, derived from the normal population, for the calculation of body composition in children treated for ALL. The mechanism of onset of obesity remains unclear, but is probably multifactorial and related to previous cranial irradiation.

Hypothalamic-pituitary-ovarian dysfunction after prepubertal chemotherapy and cranial irradiation for acute leukaemia

BACKGROUND

We assessed adult hypothalamic-pituitary-ovarian function following treatment with chemotherapy and cranial irradiation for childhood acute lymphoblastic leukaemia.

METHODS

The patients (n = 12) had median age at diagnosis of 4.7 years, and at assessment of 20.8 years. They collected a daily urine sample over two to five consecutive menstrual cycles (total of 41 cycles) for analysis of LH and steroid excretion. Blood sampling and ovarian ultrasound examination was performed in the early follicular phase. Sixteen healthy women with regular menstrual cycles were recruited as controls.

RESULTS

Urinary LH excretion was significantly lower in patients throughout the cycle, particularly during the LH surge (P < 0.0001). The length of the luteal phase was significantly shorter in patients than in normal controls (12.2 +/- 0.3 versus 13.6 +/- 0.4 days, P = 0.01) with a high prevalence of short (< or =11 days) luteal phases (15/39 cycles). Luteal phase pregnanediol excretion was slightly but not significantly lower. Follicular and luteal phase excretion of oestrone was lower in patients than in controls (P = 0.01). Early follicular phase plasma oestradiol was also lower in the patient group (P = 0.032) although LH, FSH, inhibin A and B concentrations were similar.

CONCLUSIONS

These data indicate that treatment for childhood leukaemia results in subtle ovulatory disorder in some patients, probably related to cranial irradiation. Follow-up of these women is required to detect any effect on reproductive potential.

Risk factors for excess weight gain in children treated for acute lymphoblastic leukaemia

OBJECTIVE

To test whether excess weight gain in patients treated for childhood acute lymphoblastic leukaemia (ALL) was predictable using patient characteristics at diagnosis.

DESIGN AND SUBJECTS

Longitudinal study of changes in body mass index (BMI) in all 98 patients treated in Scotland on treatment protocol MRC UKALL-XI who had reached at least 3y post-diagnosis in first remission.

MEASUREMENTS

The influence of the following variables on changes in BMI, expressed as a standard deviation score (SDS), was tested using variable selection techniques and classification and regression trees: BMI SDS at diagnosis; age at diagnosis; gender; socioeconomic status; treatment.

RESULTS

Prevalence of obesity (BMI SDS>2.0) was <2% at diagnosis, but increased to 16% at 3y. Gain in BMI SDS was significantly inversely influenced by BMI SDS at diagnosis (P<0.01) and age at diagnosis (P<0.01).

CONCLUSION

Obesity is common in ALL by the end of therapy, and is more likely in children who are younger and thinner at diagnosis. Excess weight gain was not readily predictable from routinely collected information available at diagnosis and so all children treated for ALL should be considered 'at risk' of excess weight gain and the target of obesity prevention.

Changes in body mass index and prevalence of overweight in survivors of childhood acute lymphoblastic leukemia: role of cranial irradiation

BACKGROUND

The risk factors responsible for an increased prevalence of obesity or overweight in survivors of acute lymphoblastic leukemia (ALL) remain controversial. We evaluated changes in body mass index (BMI) in a cohort of ALL survivors, all of whom have been followed until completion of linear growth.

PROCEDURE

BMI (weight/height(2)) was used as an index of adiposity and was calculated at diagnosis, at the end of treatment, and at attainment of final height in a cohort of 126 (59 males) survivors of ALL. BMI was adjusted for age and sex by computing a BMI standard deviation score (SDS) or z score. The spectrum of therapies used included intrathecal chemotherapy given alone (n = 38) or combined with cranial irradiation (CRT; 18 Gy, n = 35; 24 Gy, n = 53) and exposure to prednisone at a low dose (<3.5 gm, n = 49), medium dose (3.5-9.4 gm, n = 46), or high dose (>9.4 gm, n = 30).

RESULTS

Overall, mean +/- SEM BMI-SDS increased significantly between diagnosis (-0.18 +/- 0.08) and the end of therapy (0.41 +/- 0.09, P < 0.01), with no significant change thereafter. For patients without CRT, mean BMI-SDS remained unchanged, whereas, for those so treated, mean BMI-SDS increased significantly between diagnosis and the completion of therapy (P < 0.001). The change in mean BMI-SDS was greater in the 24 Gy group vs. the 18 Gy CRT sample (P < 0.005). In a multivariate logistic regression model, CRT was an independent predictor of being overweight (BMI >/=85 percentile) at attainment of final height [odds ratio = 1.6 (95% confidence interval 1.0-23. 1)]. The percentage of subjects who were overweight at attainment of final height was 10.5%, 40%, and 38% for subjects treated with no CRT, 18 Gy CRT, or 24 Gy CRT, respectively (P < 0.01).

CONCLUSIONS

Children with ALL given CRT develop increases in their BMI-SDS early on and during treatment and remain at significant risk for becoming overweight as young adults, a development that may increase their already heightened risk for various adverse health outcomes.

Obesity in leukemia survivors: the familial contribution

A high prevalence of obesity in survivors of acute lymphoblastic leukemia (ALL) has been described, but genetic and social influence in obesity has not been analyzed in this group of patients. The authors studied a population of 33 long-term (25 females, 8 males) in first remission who had reached their final height. All patients received cranial irradiation as part of their central nervous system (CNS)-directed therapy and no patient received growth hormone. The body mass index (BMI: weight/height2) of patients and their biological parents was calculated and submitted to statistical analysis. Obesity was defined as BMI greater than the 85th centile. No excessive obesity was found among the males at final height. Fifty-six percent of the females were obese. In this group of 14 obese female survivors 59% had obese mother, but only 14% had obese fathers. The results indicate a significant maternal predisposition to obesity.

Sexually dimorphic and radiation dose dependent effect of cranial irradiation on body mass index

OBJECTIVES

To investigate the relation between cranial irradiation received during treatment for childhood leukaemia and obesity at final height.

DESIGN

Retrospective cross sectional study.

SETTING

Paediatric oncology centres at Great Ormond Street Hospital for Children and the Royal Marsden Hospital.

SUBJECTS

Survivors of childhood leukaemia who received cranial irradiation, were in continuous first remission, and had reached final height. An unirradiated group of patients from the United Kingdom acute lymphoblastic leukaemia XI trial was also included; these patients were in continuous first remission and had been followed for at least four years from diagnosis.

MAIN OUTCOME MEASURES

Body mass index standard deviation score (BMI z score) at final height for irradiated patients and at most recent follow up for unirradiated patients. Regression analysis was used to examine the effect on BMI z score of sex, age at diagnosis, and the dose of radiation received.

RESULTS

For cranially irradiated patients, an increase in the BMI z score at final height was associated with female sex and lower radiation dose, but not with age at diagnosis. Severe obesity, defined as a BMI z score of > 3 at final height, was only present in girls who received 18-20 Gy irradiation and had a prevalence of 8%. Both male and female unirradiated patients had raised BMI z scores at latest follow up and there was no association with age at diagnosis.

CONCLUSIONS

These data are further evidence for a sexually dimorphic and dose dependent effect of radiation on the human brain.

Relative osteopenia after treatment for acute lymphoblastic leukemia

Osteoporosis in adult life is associated with a significant morbidity and may be predisposed to by osteopenia and failure to reach peak bone mass in childhood. Children treated for acute lymphoblastic leukemia (ALL) may be at risk of osteopenia as a result of previous therapy or as a consequence of the disease process itself. Dual energy x-ray absorptiometry measurements of bone mineral content (BMC) for the whole body and at the lumbar spine and hip were taken in 35 (14 male) long-term survivors of ALL and compared with results in 20 (10 male) survivors of other malignancies and 31 (17 male) healthy sibling controls. The measured BMC was expressed as a percentage of a predicted value derived from the control group and based on the variables that had influence upon it. BMC (%) was reduced at the spine in the ALL group compared with controls [92.4 (8.0)% versus 100.4 (9.7)%, respectively; p < 0.005] and at the hip compared with both other malignancies and controls [89.0 (11.5)% versus 96.1 (11.7)% and 100.4 (9.2)%, respectively; p < 0.0005]. Increasing length of time off therapy was associated with a significant increase in %BMC at both the spine and the hip. For the spine, this association was significantly different between the ALL group and other malignancies, suggesting that any gain in %BMC after therapy was slower in children treated for ALL. Both exercise capacity and levels of physical activity were correlated with %BMC at the hip (r = 0.44, p < 0.001 and r = 0.29, p < 0.01, respectively). Previous exposure to methotrexate, ifosfamide, and bleomycin was associated with a reduction in %BMC at the spine. Exposure to 6-mercaptopurine and cisplatin was associated with a reduction at the hip. In conclusion, children treated for ALL are osteopenic. The mechanism is probably multifactorial but is partially related to previous chemotherapy, limited exercise capacity, and relative physical inactivity.

Long-term neuro-endocrine sequelae after treatment for childhood medulloblastoma

The occurrence of neuro-endocrine deficiencies following craniospinal irradiation for medulloblastoma is well known, but data concerning the spectrum and prevalence of endocrine abnormalities in adulthood are scarce. We studied endocrine function in 20 (median age 25 years) adult subjects, 8-25 years (median 16 years) after therapy. The radiation dose to the whole cranium and spinal axis was 35 +/- 2.6 Gray (mean +/- standard deviation) with a boost to the posterior fossa of 18 +/- 3.7 Gray. 13 subjects had received additional chemotherapy. In 15 of 20 (75%) subjects, endocrine abnormalities were observed. In 14 (70%), growth hormone (GH) secretion was impaired; 7 (35%) subjects had an absolute GH deficiency, while 7 (35%) showed subnormal responses to insulin-induced hypoglycaemia. In contrast, only 20% (4) of these subjects showed impairment of the hypothalamus-pituitary-thyroid (HPT) axis, while 15% (3) showed central impairment of hypothalamus-pituitary-gonadal (HPG) function. Central impairment of the HPG axis was associated with impaired GH secretion in all cases. Central adrenal insufficiency was not observed. Basal levels of prolactin were normal in all subjects. Young age at treatment was a determinant of GH deficiency in adulthood (P = 0.014). Neither post-treatment interval, nor the use of chemotherapy were determinants of central endocrine impairment in adulthood. In long-term survivors of medulloblastoma, GH deficiency has a high prevalence. In contrast, impairment of the HPG and HPT axis is less common, while central adrenal insufficiency was not observed.

Growth and endocrinological disorders up to 21 years after treatment for acute lymphoblastic leukemia in childhood

BACKGROUND

Our aim was to evaluate endocrinological status 10-21 years after treatment for childhood acute lymphoblastic leukemia (ALL) with chemotherapy (C) and cranial irradiation (C + I) or only C, and to correlate the endocrine data with growth parameters.

PROCEDURE

Of 30 patients (15 females and 15 males), 18 were treated with C + I and 12 were treated with C only. Height standard deviation score (HSDS) and body mass index standard deviation score (BMISDS) before treatment, at end of treatment, and at follow-up were calculated from height and weight registered from the charts. At follow-up examinations, provocative growth hormone (GH) tests (clonidine and insulin tolerance test) and an ACTH test were performed. Furthermore, blood samples for hormonal analysis, IGF-I, IGFBP-3, GHBP, and leptin were drawn.

RESULTS

Eleven patients (9 treated with C + I and 2 treated with C) showed insufficient response to GH tests. Two patients had hypogonadism. HSDS and IGF-I were significantly lower and GHBP significantly higher in GH-deficient patients compared to the group with normal GH secretion at follow-up. BMISDS steadily increased from start of treatment until follow-up, independent of GH status at follow-up. BMISDS at follow-up was positively correlated with serum leptin (P < 0.001), and serum leptin was significantly higher in the cranial irradiated group as compared to the nonirradiated group.

CONCLUSIONS

GH deficiency is frequently found at long-term follow-up in patients treated for childhood ALL. Other hormonal deficiencies are rare. HSDS at long-term follow-up is dependent on GH secretory status. Long-term endocrinological follow-up examinations in patients treated for childhood ALL are recommended, as hormonal replacement therapy may be indicated.

Growth hormone status in adults treated for acute lymphoblastic leukaemia in childhood

OBJECTIVE

Growth hormone status was assessed in a cohort of 32 (16 male) adults who had received cranial irradiation (XRT) in childhood as part of their treatment for acute lymphoblastic leukaemia (ALL) and compared with 35 age matched young adults (18 male).

DESIGN

Height and weight were measured in all subjects and the heights of the patients at XRT were obtained from their case notes. Each patient and control underwent two provocative tests of growth hormone (GH) secretion using insulin (0.2 IU/kg body weight) and arginine (20 g/m2). Basal serum insulin like growth factor-1 (IGF-1) and IGFBP-3 (binding protein-3) concentrations were also measured.

RESULTS

The patient group had a significantly lower peak GH response to both provocative tests (P < 0.01), and lower IGF-1 and IGFBP-3 levels compared with the normal controls (P < 0.01). Nine of the patient group were severely GH deficient (peak GH response < 9 mU/l to both provocative agents) and a further 12 patients were GH insufficient (peak GH response < 20 mU/l to both tests with at least one peak GH response > 9 mU/l). Overall a significant median change in height from XRT to final height of -0.5 SDS was found which was even greater in the severely GH deficient group (median change in height of -2.1 SDS).

CONCLUSION

These data suggest that a significant proportion of adults treated with cranial XRT in childhood with irradiation doses between 18-25 Gy, as part of their treatment for ALL, are severely GH deficient now and should be considered for GH replacement. Changes in GH secretion evolve with time following irradiation-induced damage to the hypothalamic-pituitary axis; therefore long-term surveillance will be required in those remaining patients, in whom GH status is considered currently to be insufficient or even normal.

Daily energy expenditure and physical activity in survivors of childhood malignancy

Changes in body composition, in particular the onset of obesity, may result from reductions in total daily energy expenditure (TDEE) as a consequence of relative physical inactivity. Children previously treated for acute lymphoblastic leukemia (ALL) become obese, yet the mechanism remains undefined. TDEE and physical activity levels [PAL = TDEE/basal metabolic rate (BMR)] were measured in 34 long-term survivors of ALL and compared with results from 21 survivors of other malignancies and 32 healthy sibling control subjects using the flex-heart rate technique. Body composition was measured by dual energy x-ray absorptiometry. The median TDEE was reduced in the ALL group (150 kJ x kg d(-1)) compared with other malignancies and controls (207 and 185 kJ x kg d(-1), respectively, p < 0.01). This reduction was accounted for mainly by a relative decrease in the PAL of the ALL group (1.24) compared with both other malignancies and controls (1.58 and 1.47, respectively, p < 0.01). TDEE and PAL were correlated with percentage body fat (r = -0.39, p < 0.001 and r = -0.24, p < 0.05, respectively). Obesity in survivors of ALL may, in part, be explained by a reduction in TDEE as a consequence of reduced PAL. The cause of such reduction is uncertain.

Systematic approach for detection of endocrine disorders in children treated for brain tumors

Endocrine dysfunction can be challenging to diagnose in children treated for brain tumors. Treatments are available for hormonal replacement and when necessary, hormonal suppression. Without these endocrine treatment regimens, life can be unnecessarily difficult or unpleasant. An endocrine survey can be used to screen at-risk neuro-oncology patients once or twice a year to facilitate the recognition of endocrine dysfunction. It is hoped that through the use of a routine screening program, physicians will be able to diagnose and begin treatment of endocrine problems in a time-efficient manner.

Growth and growth hormone secretion after treatment for childhood non-Hodgkin's lymphoma

The aim of this study was to evaluate the growth and growth hormone (GH) secretion, as assessed by the rate and pattern of secretion, in patients in remission from non-Hodgkin's lymphoma (NHL) who had been treated with corticosteroids and intense chemotherapy. None of the patients had received cranial irradiation. Twelve children were investigated yearly by taking 24-hour GH profiles starting 1 year from the time of diagnosis. The mean age at onset of the disease was 7.5 years. Another 12 young adults were studied in a cross-sectional manner 4.1-21.3 years (mean, 9.0 years) after diagnosis of NHL. The mean age at onset of the disease was 10.7 years. The median height velocity was significantly decreased during the 1st year following diagnosis (standard deviation scores [SDS] -0.15, P < .001), especially during the first 3 months (SDS -0.75, P < .001) when the most intense treatment was given. During the 2nd year height velocity was still somewhat reduced (SDS -0.13, P < .001). However, there was no reduction in final attained height. Spontaneous GH secretion, in terms of both secretory rate and pulsatile pattern, was evaluated by measuring integrated GH concentrations in 20-minute blood samples collected over a 24-hour period. The plasma GH concentrations were transformed into GH secretion rates by means of a deconvolution technique. Fourier time series analysis was applied to determine possible disturbances of rhythmicity of the GH secretion. The GH secretion rate and the pulsatile pattern of secretion in the NHL patients were similar to those of the reference population of pubertal matched healthy controls. There was no influence of the age at diagnosis or of the time from diagnosis of NHL on the GH secretion rate. Growth impairment in children with a malignant disease treated only with steroids and chemotherapy is therefore probably not caused by disturbed GH secretion, but rather by direct interference with bone growth of the cytotoxic drugs used. There was no significant influence on weight gain during the treatment period so an indirect effect of chemotherapy on bone growth through interference with adequate nutrition seems unlikely. However, GH secretion was not evaluated during the period of growth retardation, and therefore a transient deficiency was not excluded.

Two types of growth hormone rhythm in boys with constitutional short stature

The relationship between temporal and quantitative changes in pulsatile growth hormone (GH) secretion and growth of constitutionally short children (CSS) was studied in 19 prepubertal boys and 4 with early adrenarche aged 7.8 to 14 years. Continuous plasma GH monitoring was performed at 30 minutes intervals during 24 hours. The data were analysed by single and serial best fit (BFT) cosinor analysis for rhythm parameters and the Pulsar peak detection program for determining pulsatile properties. The pulsatile patterns were expressed in mean GH concentration, area under the curve, mean pulse area and maximal pulse height but not in the number of pulses. Thirteen out of 23 patterns exhibited significant 24-h compatible rhythms. The studied cohort was divided into two groups, those who exhibited the 24-h circadian rhythm (CIR) and those who lacked it (NCIR). Ultradian 2.5-4 h rhythms were observed in all patients. The NCIR children were significantly shorter than the CIR group (p = 0.017). The CIR boys secreted a significantly higher (p = 0.01) amount of GH during the 24-h span, most of which was during sleep. Our data indicate that the magnitude of pulses rather than their number is responsible for the quantitative differences observed between the two groups of boys with CSS. It is suggested that a lack of 24-h rhythmicity and the associated reduced nocturnal pulsatility play a role in the manifestation of short stature.

Shortened and diminished pubertal growth in boys and girls treated for acute lymphoblastic leukaemia

Statural growth during puberty was studied longitudinally in 28 patients treated for acute lymphoblastic leukaemia. All patients received prophylactic cranial irradiation. The age at diagnosis was below 7 years, the age at final investigation was above 16 years for girls and above 18 years for boys. Growth was analysed using the Kernel estimation. In girls the onset of puberty and menarche was at a younger age, as compared to reference values, and the duration of the pubertal growth spurt was shorter. Compared to early maturing girls, the growth velocity at peak height velocity was lower. This resulted in a final height which was shorter than expected on the basis of the height standard deviation score before the start of puberty. In boys the duration of the pubertal growth spurt was shorter and the height gain during the growth spurt less than in the reference population. In both sexes the bone age development was accelerated.

Influence of treatment modalities on body weight in acute lymphoblastic leukemia

Weight for height of 92 patients (51 girls and 41 boys) treated for acute lymphoblastic leukemia (ALL) was evaluated in a longitudinal study. Fifty-four patients received cranial irradiation (CI) with a dose of 18 or 24 Gy and 38 patients did not receive CI. Seventy-seven patients were treated according to a normal-risk protocol and 15 patients received more intensive chemotherapy according to a high-risk protocol. In most of the patients the duration of follow-up was 12 years for irradiated patients and 4.5 years for the nonirradiated patients. Thirty of 92 patients were treated according to a protocol without CI, but with a difference in the use of corticosteroids: 19 patients received dexamethasone during the remission-induction and maintenance treatment and 11 patients received prednisone. The influence of dexamethasone vs. prednisone, sex, CI and high-dose vs. low-dose chemotherapy on weight for height was evaluated. Patients who received dexamethasone showed a significant increase in weight for height immediately after the start of therapy. In patients who received CI, weight for height significantly increased after the first year of treatment. The overweight in these patients persisted during the whole follow-up period. The weight for height of patients treated with prednisone and of patients who did not receive CI was below the mean of the normal population during treatment but was not different from normal after cessation of therapy. No difference in weight gain was seen between boys and girls and between patients who were treated with high vs. normal-risk protocols.

Growth, puberty and obesity after treatment for leukaemia

Final height, body proportions, pubertal growth and body mass index were studied retrospectively in 142 survivors of acute lymphoblastic leukaemia (ALL). Treatment consisted of combination chemotherapy and cranial irradiation (18 or 24 Gy). Significant standing height loss and disproportion, with a relatively short back, was seen in both radiation dose groups. Girls were more severely affected than boys. Pubertal growth was adversely affected, with a reduction in peak height velocity in both sexes. Puberty occurred early in girls but at the normal time in boys. Nearly half the group were obese at final height, with no significant difference in incidence between the sexes. The relative roles of cranial irradiation and chemotherapy in the disturbance of growth, puberty and body composition observed in survivors of childhood ALL remain unclear. The aetiology is almost certainly multifactorial, with radiation-induced growth hormone insufficiency, early puberty, steroids and chemotherapy all having a role.

High incidence of obesity in young adults after treatment of acute lymphoblastic leukemia in childhood

To determine whether obesity complicated the treatment of childhood acute lymphoblastic leukemia, we studied the body mass index (BMI) of 63 female when and 51 male patients from the time of diagnosis of acute lymphoblastic leukemia to the time when final height was attained. The BMI z score was calculated for each patient at diagnosis, at end of treatment, and at attainment of final height. Obesity at attainment of final height was defined as a BMI greater than the 85th percentile of the normal reference population. At final height 23 of 51 male (45%) and 30 of 63 female patients (47%) were obese. Girls became obese between diagnosis and the end of chemotherapy (p = 0.02), after which they had no further increase, indicating that chemotherapy may have played a role in their obesity. Boys had a progressive and gradual increase in BMI z score through to attainment of final height. Obesity did not appear to be associated with growth hormone insufficiency, disproportionate growth, or abnormal timing of puberty. We conclude that approximately half the survivors of leukemia in childhood become obese young adults. Many of those treated with the more recent regimens studied are still only in their mid or preteen years and should be advised regarding a more active lifestyle and a healthy diet in an attempt to reduce the incidence of obesity.

Reduced growth hormone secretion with maintained periodicity following cranial irradiation in children with acute lymphoblastic leukaemia

OBJECTIVE

Low dose cranial irradiation in children with acute lymphoblastic leukaemia (ALL) has been reported to reduce GH secretion in puberty. A recent study also reported a disturbed periodicity of GH secretion during puberty. We have focused on the different stages of puberty in studying these two parameters of GH secretion and have also compared the effects of 18 vs 24 Gy radiation dose.

PATIENTS AND MEASUREMENTS

Thirty-four children previously treated for ALL were compared with a control group of 208 healthy normally growing children. GH secretion was measured as 24-hour profiles.

RESULTS

In children treated for ALL, GH secretion rate and GH peak amplitude were below the median values for controls, both before puberty and during all stages of puberty. The difference between patients and controls was most pronounced in late puberty. Radiation with 18 or 24 Gy gave similar results. However, time sequence analysis showed a similar periodicity of GH secretion in both patient and control groups before, as well as during, puberty. Thus, before puberty a broad range of cycles per 24 hours was seen. These synchronized during puberty to a predominant GH peak frequency of one every 3-4 hours.

CONCLUSIONS

After low dose cranial irradiation with 18 or 24 Gy, the total amount of GH secreted is reduced both before and during puberty. We could not confirm previous findings of impaired periodicity of GH secretion in these children.

Normal final height after treatment for acute lymphoblastic leukemia without irradiation

In order to evaluate the influence of chemotherapy on linear growth, 28 children treated for acute lymphoblastic leukemia without irradiation were evaluated before, during and after the end of therapy. Median age at diagnosis was 4.4 years (range 2.2-12.7 years) and treatment was discontinued after a median period of 3.1 years (3.0-5.2 years). We observed a significant decrease in height SDS (p = 0.006) from diagnosis to the end of chemotherapy, followed by catch-up in height SDS from the end of chemotherapy to final observation. Catch-up growth took place mainly within the first 2 years after cessation of therapy. In 22 patients final height was reached. Final height was normal (median height SDS -0.035) and even significantly higher than mid-parental height SDS (p = 0.012). In those patients who attained adult stature, the sitting height to standing height ratio was also normal. In conclusion, in children treated for acute lymphoblastic leukemia, chemotherapy exerted a negative influence on growth, but catch-up occurred within 2 years after cessation of therapy, resulting in normal final height and body proportions.

Longitudinal growth and final height in long-term survivors of childhood leukaemia

Survival of children with acute lymphoblastic leukaemia (ALL) has increased considerably in recent years and data on the spontaneous growth and final height of these children are conflicting. Therefore, we analysed the longitudinal growth and final height in 52 survivors (33 females, 19 males) of childhood ALL. These children were diagnosed and treated in a single institution, all remained in first remission and were submitted to cranial irradiation with either 2400 or 1800 cGy. None of the patients received testicular or spinal irradiation. Median age at diagnosis was 4.2 (range 1.3-9.6) years in the first group (2400 cGy) and 3.9 (0.8-10.5) years in the second (1800 cGy). Standing height was measured at diagnosis, at the end of treatment (median 3.1 years after diagnosis), 6, 12, 24 months after the end of treatment, and finally at the completion of growth. In girls a significant decrease of mean height standard deviation score (SDS) during treatment and a catch up in growth after the end of therapy was followed by a second period of reduced growth. Mean final height SDS was significantly lower than the value at diagnosis in both groups of girls, but only in males treated with 2400 cGy. Mean overall loss in height SDS from diagnosis to final height was higher in females (-1.24) than in males (-0.40) (P = 0.009). Females < or = 4 years of age at diagnosis showed a higher loss in final height than females > 4 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Patterns of obesity in boys and girls after treatment for acute lymphoblastic leukaemia

The frequency and pattern of obesity in survivors of acute lymphoblastic leukaemia (ALL) was examined in a retrospective analysis of height and weight at zero, two, and four years from diagnosis in 40 children (19 boys and 21 girls). The children had been treated according to the Medical Research Council protocols UKALL VIII and X, both of which included cranial radiotherapy at a dose of 1800 cGy. Body mass index (BMI), determined as weight/height, was used as a measure of fatness. The BMI Z scores were calculated for each patient from standard tables. The ALL group was compared with a control group of 18 age matched children who had received chemotherapy but no radiotherapy. Changes in BMI between diagnosis and two and four years later were analysed by paired t tests. Mean BMI Z scores at diagnosis were similar between ALL boys, ALL girls, and the control group. Two years after diagnosis the ALL group, particularly the girls, showed a significant increase in BMI. By four years BMI had decreased slightly in the ALL boys, but had increased still further in the ALL girls with 57% having BMI Z scores greater than 2. In the control group BMI increased, but not significantly, at two and four years. It is concluded that the obesity seen in patients treated for ALL is more pronounced in girls than boys, and that cranial irradiation is an important factor.

Pubertal growth in response to testosterone replacement therapy for radiation-induced Leydig cell failure

The adolescent growth pattern of eight boys, who had puberty induced with androgen replacement therapy following radiation-induced Leydig cell failure, was studied from induction of puberty at a mean age of 13.1 years (range 11.6-14.5) to final height at mean age of 18.8 years (range 17.7-20.3). The mean gains during puberty (SD) for standing height, sitting height, and sub-ischial leg length were 18.56 cm (3.98), 10.46 cm (2.39), and 8.1 cm (2.01) respectively, which were significantly reduced compared with normal Tanner standards (P < .001). The peak velocity for each parameter occurred in the 1st year of induced puberty in contrast to the pattern in normal adolescence, although the mean peak velocity for each auxological parameter was not significantly different from the normal Tanner standards. The mean adult standing height (SD), 167.5 cm (9.88), and mean adult leg length (SD), 80.8 cm (6.19), were not significantly different from the normal Tanner standards, whereas the mean adult sitting height (SD), 86.7 cm (4.78), was shorter (P < .001). Three of the eight patients had a leg length standard deviation score less sitting height standard deviation score in excess of +2.96 suggesting the presence of significant skeletal disproportion. Seven of the eight boys reached target genetic height, though in six, the final height was below mid-parental height (P < .05). The modest loss in height potential was mainly due to radiation-induced skeletal dysplasia attenuating the growth of the spine. The families of boys with radiation-induced Leydig cell failure requiring androgen replacement therapy can be reasonably optimistic about height prognosis as seven of the eight boys reached target genetic height.

Adrenocorticotrophin and cortisol secretion in children after low dose cranial irradiation

OBJECTIVE

We investigated the effect of low dose cranial irradiation (18-24 Gy) on spontaneous ACTH and cortisol secretion in children.

DESIGN

We analysed 24-hour plasma ACTH and cortisol profiles sampled at 20-minute intervals.

PATIENTS

Twenty long-term survivors of acute lymphoblastic leukaemia were studied and results compared with those in 14 normal children.

MEASUREMENTS

ACTH and cortisol profiles were analysed by Fourier transformation and spectral analysis of stationarized data, autocorrelation and coherency analysis.

RESULTS

The normal circadian rhythms of ACTH and cortisol were preserved in the children after cranial irradiation. The median 0900 h and midnight values were 1.50(0.8-6.4)pmol/l and 1.0(0.6-3.7)pmol/l respectively for ACTH and 282(48-1913)nmol/l and 57.5(44-637)nmol/l respectively for cortisol, and were not significantly different from those in the normal group. Fourier transformation revealed dominant periodicities for ACTH at 0.7-1.1 h, equivalent to 22-34 ACTH secretory bursts per 24 hours, and for cortisol at 0.7-1.1 h and 2-4.8 h. Similar results were found in the normal group. Coherency analysis indicated a significant shared periodicity of 0.7-1.2 h in nine children, corresponding to 20-34 related secretory bursts in 24 hours for ACTH and cortisol. After pooling the coherency spectra in the cranially irradiated group, comparison with the pooled data from the normal group revealed no significant difference between the two groups in the relationship between the two hormones.

CONCLUSION

No significant disruption of spontaneous ACTH or cortisol secretion, either in the amount or pattern of hormones secreted, was found in children after low dose cranial irradiation (18-24 Gy).

Irradiation-induced growth failure

GH deficiency, skeletal disproportion and early or precocious puberty may complicate irradiation to the head or axial skeleton in childhood. Certain cohorts of children are at particular risk, including those irradiated for brain tumours and various haematological malignancies. Both GH deficiency and impaired spinal growth may result in short stature, whereas the occurrence of early puberty in association with GH deficiency reduces the time available for GH therapy. The age of the child at irradiation is critical in that, in younger children, the central nervous system is more radiosensitive, the severity of the subsequent skeletal disproportion is greatest and the onset of puberty earliest. It is the very young craniospinally-irradiated child who is most at risk of extreme short stature.