Pulsatile growth hormone secretion in children with acute lymphoblastic leukemia after 1800 cGy cranial radiation

Differential Diagnosis of the Short IGF-I-Deficient Child with Apparently Normal Growth Hormone Secretion

The current differential diagnosis for a short child with low insulin-like growth factor I (IGF-I) and a normal growth hormone (GH) peak in a GH stimulation test (GHST), after exclusion of acquired causes, includes the following disorders: (1) a decreased spontaneous GH secretion in contrast to a normal stimulated GH peak ("GH neurosecretory dysfunction," GHND) and (2) genetic conditions with a normal GH sensitivity (e.g., pathogenic variants of GH1 or GHSR) and (3) GH insensitivity (GHI). We present a critical appraisal of the concept of GHND and the role of 12- or 24-h GH profiles in the selection of children for GH treatment. The mean 24-h GH concentration in healthy children overlaps with that in those with GH deficiency, indicating that the previously proposed cutoff limit (3.0-3.2 μg/L) is too high. The main advantage of performing a GH profile is that it prevents about 20% of false-positive test results of the GHST, while it also detects a low spontaneous GH secretion in children who would be considered GH sufficient based on a stimulation test. However, due to a considerable burden for patients and the health budget, GH profiles are only used in few centres. Regarding genetic causes, there is good evidence of the existence of Kowarski syndrome (due to GH1 variants) but less on the role of GHSR variants. Several genetic causes of (partial) GHI are known (GHR, STAT5B, STAT3, IGF1, IGFALS defects, and Noonan and 3M syndromes), some responding positively to GH therapy. In the final section, we speculate on hypothetical causes.

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.

Pediatric Hodgkin lymphoma survivors at negligible risk for significant bone mineral density deficits

BACKGROUND

We hypothesized that pediatric Hodgkin lymphoma (HL) survivors would have bone mineral density (BMD) deficits compared to their peers because of osteotoxic chemotherapy during the time of greatest BMD accretion.

METHODS

We retrospectively reviewed records of HL survivors returning for follow-up between 1990 and 2002. Of the 133 eligible survivors, 109 who underwent quantitative computed tomography (QCT) comprised the study group. QCT-determined BMD Z-scores were correlated with patient characteristics and therapeutic exposures by Wilcoxon rank sum or Chi-square tests. Logistic regression models were used to explore risk factors for diminished BMD.

RESULTS

The study cohort was half male (50.5%) and 85.3% reported their race as white. Participants were representative of all survivors potentially eligible for study, except that more study participants were female, had hypothyroidism, and had received cyclophosphamide. Median age at diagnosis was 15.1 years (range, 3.1-20.7 years); median time between diagnosis and QCT was 7.5 years (range, 5.0-12.4 years). The proportion of HL survivors with BMD below the mean did not significantly differ from the general population (P = 0.503). However, those with BMD -1.5 SD and BMD -2.0 SD or lower (14.7% and 7.3%, respectively) exceeded that in the general population (6.7% and 2.3%, respectively; P < 0.001 for both degrees of severity). Males, diagnosed at 14 years or older, were at 6.5 times higher risk than females (OR 95% CI: 1.24-34.14; P = 0.027) for BMD deficits.

CONCLUSIONS

Overall, pediatric HL survivors had negligible BMD deficits. Male gender was associated with an increased risk of developing BMD deficits.

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.

Changes in bone mineral density in survivors of childhood acute lymphoblastic leukemia

BACKGROUND

There is little information about factors modulating bone mineral density (BMD) in survivors of childhood acute lymphoblastic leukemia (ALL).

PROCEDURE

We analyzed data from 57 survivors (26 male, 52 Caucasian) who underwent two serial quantitative computed tomography (QCT) studies of BMD. Using multiple linear regression, we evaluated the association of BMD change with demographic variables, treatment history, hormone therapy, exercise, and tobacco and alcohol use.

RESULTS

The median age was 3.4 years (range, 0.9-17.4 years) at diagnosis of ALL; the median age at the first QCT (Study I) was 15.0 years (range, 10.6-31.0 years) and at the second QCT (Study II) was 18.2 years (range, 14.2-35.3 years). Mean height increased 4.7 cm and mean weight increased 8.8 kg between Studies I and II. While the mean BMD increased 9.33 mg/cc (P = 0.003), the BMD Z-score increased only slightly (0.21 SD, P = 0.035). Cortical bone density increased significantly (approximately 25.3 mg/cc; P = 0.001), but the ratio of trabecular to cortical BMD decreased significantly (P = 0.045). Factors independently associated with unfavorable BMD changes included older age at diagnosis (P = 0.001), female sex (P = 0.018), and nutritional supplementation (0.032). Alcohol (P = 0.009) was an unfavorable factor in a univariable analysis.

CONCLUSIONS

Bone mineral accretion during adolescence is attenuated in childhood ALL survivors by a comparative deficit in trabecular versus cortical bone deposition. BMD is influenced favorably by exercise in early adolescence and unfavorably by the use of nutritional supplements and alcohol. These results provide new information about behavioral factors that affect bone accrual in survivors of childhood ALL and warrant definitive evaluation in a larger cohort.

Endocrine complications in pediatric patients with acute lymphoblastic leukemia

Endocrine complications of therapy for acute lymphoblastic leukemia (ALL) are common and are potentially debilitating both during and after therapy. Growth velocity slows during therapy for ALL, especially during the first year; however, children who do not receive cranial irradiation usually reach normal adult height. While growth hormone deficiency generally occurs in patients who have received 24Gy of cranial irradiation, it may also develop in those treated with lower doses (18Gy) of cranial radiation or with only high-dose methotrexate. Obesity commonly occurs during therapy and persists after completion of therapy. Osteopenia can occur early during therapy for ALL and can persist for many years. Adrenal insufficiency should be suspected in any child who has recently received glucocorticoid therapy, and stress doses of steroid should be administered in the event of metabolic stress. Screening of urine is useful for early detection of hyperglycemia during therapy with glucocorticoids and L-asparaginase. The syndrome of inappropriate secretion of anti-diuretic hormone is usually associated with vincristine therapy and may be aggravated by concurrent use of azole antifungals. Finally, patients who have received 18 or 24Gy of cranial irradiation may have clinical or subclinical deficiencies of thyroid hormones.

Hypothyroidism in children with medulloblastoma: a comparison of 3600 and 2340 cGy craniospinal radiotherapy

PURPOSE

To determine if low-dose craniospinal irradiation (2340 cGy) with chemotherapy is associated with a lower incidence of hypothyroidism compared to standard dose (3600 cGy) with or without chemotherapy in children with medulloblastoma.

PATIENTS AND METHODS

Between 1980 and 1999, 32 patients < or =20 years old survived after craniospinal irradiation with or without chemotherapy. Twenty patients received 3600 cGy craniospinal irradiation (CSI), whereas 12 had 2340 cGy CSI; all patients received a posterior fossa boost to a total dose 5040-5580 cGy. The median ages at the time of CSI for those receiving 2340 cGy and 3600 cGy were 7.2 and 10.2 years, respectively. Chemotherapy (CT) was employed in 22 children. All children who received 2340 cGy had CT consisting of vincristine, CCNU, and either cisplatin or cyclophosphamide. Ten of 20 (50%) patients receiving 3600 cGy had CT; the most common regimen was vincristine, CCNU, and prednisone. Serum-free thyroxine and thyroid-stimulating hormone concentrations were measured in all children at variable times after radiotherapy. Thyroid-stimulating hormone responses to i.v. thyrotrophin-releasing hormone were assessed in those suspected of having central hypothyroidism. Median follow-up for children receiving 2340 cGy was 5 years (range: 2-11.2 years), whereas for those receiving 3600 cGy, follow-up was 12.5 years (range: 2.4-20 years).

RESULTS

Eighteen patients (56%) developed hypothyroidism at a median time after radiotherapy of 41 months (range: 10 months to 18 years). Primary hypothyroidism was more common than central hypothyroidism (38% and 19%). All 7 children <5 years developed hypothyroidism, whereas 9 of 15 (60%) ages 5-10 and 2 of 10 (20%) age >10 years had hypothyroidism (p < 0.001). Hypothyroidism was documented in 10 of 12 (83%) who had 2340 cGy + CT, 6 of 10 (60%) who had 3600 cGy + CT, and 2 of 10 (20%) who had 3600 cGy without CT (p < 0.025).

CONCLUSIONS

Current treatment regimens consisting of chemotherapy and 2340 cGy craniospinal irradiation followed by a posterior fossa boost for medulloblastoma do not show a reduction of hypothyroidism. Young age and use of chemotherapy were associated with a higher incidence of hypothyroidism.

Bone mineral decrements in survivors of childhood acute lymphoblastic leukemia: frequency of occurrence and risk factors for their development

We assessed the clinical and treatment factors that predispose survivors of childhood acute lymphoblastic leukemia (ALL) to low bone mineral density (BMD). Using quantitative computed tomography, we determined the frequency of low BMD (defined as >1.645 standard deviations (SD) below the mean) in leukemia survivors treated with multiagent chemotherapy including prednisone and antimetabolite. All participants had completed therapy at least 4 years earlier, remained in continuous complete remission, and had no second malignancies. We statistically correlated BMD results with patient characteristics and treatment histories. Among 141 survivors (median age, 15.9 years; median time after diagnosis, 11.5 years), median BMD z score was -0.78 SD (range, -3.23 to 3.61 SDs). Thirty participants (21%; 95% confidence interval, 15% to 29%) had abnormally low BMD, a proportion significantly (P < 0.0001) greater than the expected 5% in normal populations. Risk factors for BMD decrements included male sex (P = 0.038), Caucasian race (P < 0.0001), and cranial irradiation (P= 0.0087). BMD inversely correlated with cranial irradiation dose. BMD z scores of patients who received higher doses of antimetabolites were lower than those of other patients. Childhood ALL survivors are at risk to have low BMD, especially males, Caucasians, and those who received cranial irradiation.

Osteoporosis due to cancer treatment: pathogenesis and management

Many therapeutic regimens in cancer treatment carry the risk of causing or favoring the development of osteoporosis. Therapies in which hypogonadism may occur are most relevant in this respect. Prompt hormone replacement therapy is indicated in these patients. In patients in whom this is undesirable because of a hormone-dependent tumor, the risk of osteoporosis should be assessed by means of osteodensitometry, and prophylactic or therapeutic measures should be instituted if necessary. Early intervention improves outcome because osteoporosis therapy is most effective in preventing deterioration of bone mass. There remains much uncertainty in assessing the risk of combination chemotherapy with regard to the development of osteoporosis. Negative effects on the skeleton have, however, been demonstrated for individual drugs, such as methotrexate and ifosfamide. Negative effects of the tumor itself on bone metabolism may aggravate the degree of osteoporosis. Detailed data and long-term experience to assess the risk are urgently needed in this area and constitute an important research topic for the coming years and decades. This review discusses the most prevalent mechanisms of osteoporosis caused by cancer treatment and outlines therapeutic strategies for the prevention and treatment of therapy-induced bone loss.

Longitudinal study of bone age in acute lymphoblastic leukaemia

Bone age was assessed in children with acute lymphoblastic leukaemia (ALL) using the Tanner-Whitehouse II method. X-rays of the left hand (wrist) were made at diagnosis and annually until 5 years after diagnosis. A total of 164 X-rays from 40 patients was available. During treatment bone age development as well as height growth was retarded in relation to calendar age. A catch-up of bone age and height was observed in the 2 years after cessation of treatment. No significant differences could be found between patients with and without cranial irradiation as central nervous system treatment. Therefore cranial irradiation alone is not responsible for the growth retardation of children with ALL; the causative role of cytostatic drug therapy and/or corticosteroids has to be investigated.

Hyperfractionated, twice-a-day, radiotherapy may decrease IQ deterioration due to prophylactic cranial irradiation in childhood acute lymphoblastic leukemia: a radiobiological analysis

High cure rates in childhood acute lymphoblastic leukemia (ALL) are being achieved with aggressive systemic chemotherapy and treatment to sanctuary sites including prophylactic cranial irradiation. However, IQ deterioration is a dreaded complication of prophylactic cranial irradiation. IQ deterioration is a late sequela. Since there is evidence--both radiobiological and clinical--to suggest that acute tissue (including tumor) response and late tissue response can be separated by hyper-fractionation, we propose a twice-a-day radiotherapy in prophylactic cranial irradiation of childhood ALL to decrease delayed toxicity. Analysis based on current radiobiological models favors such a treatment scheme. However, only a prospective clinical trial can confirm whether IQ deterioration can be prevented or decreased with hyper-fractionated radiotherapy.

Radiation and hypothalamic-pituitary function

In adults, hypopituitarism is a common consequence of external radiotherapy. The clinical manifestations may be subtle and develop insidiously many years after radiotherapy. Anterior pituitary deficiencies can therefore only be detected by regular testing, including dynamic tests of GH and ACTH reserve. Although the deficiencies most commonly develop in the order GH, gonadotrophins, ACTH then TSH, this sequence may not be predictable in an individual patient and comprehensive testing is therefore required. The tests should ideally be performed annually for at least 10 years after treatment or until deficiency has been detected and treated. It is not only the patients with pituitary disease who are at risk of developing hypopituitarism after radiotherapy. Any patient who receives a total dose of irradiation of 20 Gy or more to the hypothalamic-pituitary axis is at risk of hypopituitarism, although the threshold dose may be lower than this. This is particularly important in the long-term survivors of malignant disease in whom endocrine morbidity may be relatively common and in whom this can be easily treated, with consequent improvement in quality of life. Whilst patients who receive a high total dose of irradiation are at increased risk of developing multiple deficiencies, a higher fraction size also increases the risk of anterior pituitary failure. There is good evidence that the earliest damage to the hypothalamic-pituitary axis after external radiotherapy is at the level of the hypothalamus. However, patients who undergo pituitary ablation with interstitial radiotherapy or heavy particle beams are likely to sustain direct damage to the pituitary. In these patients, the sequence in which individual pituitary hormone deficiencies develop is generally the same as that observed with the hypothalamic damage after conventional external radiotherapy. The increasing use of radiotherapy as a means of treatment for malignant disease means that new groups of patients with potential for endocrine dysfunction are emerging. Whole body irradiation in the preparation for bone marrow transplant is one such treatment and although hypothalamic-pituitary damage appears to be confined to GH deficiency in children, longitudinal experience is limited to date, particularly in adults. The treatment of malignant disease in childhood is of particular importance in terms of the delayed endocrine sequelae. The hypothalamic-pituitary axis may not be the only endocrine tissue damaged by treatment in these patients and management is therefore more complicated. In the growing child, the potential association of growth hormone deficiency, gonadal failure or premature puberty and thyroid dysfunction mean that expert endocrine supervision is essential for optimum long-term outcome.