Hypothalamic hypopituitarism following cranial irradiation for nasopharyngeal carcinoma

Survival outcomes, hematologic complications and growth impairment after sequential chemoradiotherapy in intracranial NGGCTs: a retrospective study

PURPOSE

This study aimed to evaluate the clinical features, prognostic factors, and survival outcomes for patients with intracranial nongerminomatous germ cell tumors (NGGCTs), with a particular focus on treatment toxicity for long-term survivors.

METHODS

Intracranial NGGCTs treated with platinum-based chemotherapy and craniospinal irradiation (CSI) in our institution were retrospectively analyzed. Hematological complications following sequential chemoradiotherapy as well as height and weight in childhood survivors were evaluated. Plasma growth hormone (GH) concentrations prior to and after radiotherapy were obtained for the comparisons.

RESULTS

A total of 111 intracranial NGGCTs were included. The 3‑year overall survival (OS) and event-free survival (EFS) rates were 83.5% ± 3.9% and 71.0% ± 4.8%, respectively. A combined treatment modality consisting of ≥ 4 cycles of platinum-based chemotherapy and CSI was associated with an improved OS (P = 0.003) and EFS (P < 0.001). Thrombocytopenia of any grade occurred in 35.4% (34/96) of patients, and the threshold age for an increased risk of thrombocytopenia was 14 years (area under the curve AUC = 0.752, P < 0.0001) as derived from receiver operating characteristic (ROC) analysis. Growth impediment was found in 8 of 56 (14%) patients. The age for receiving radiotherapy was found to inversely correlate with height development, revealing a cut-off age of 11.5 years for risking growth impairment (AUC = 0.806, P = 0.004). Consistently, a significant decline in plasma growth hormone after radiotherapy was observed in patients ≤ 11.5 years (P < 0.01) but not patients > 11.5 years. (P > 0.05).

CONCLUSION

Our study suggested that a combined treatment modality with at least four cycles of chemotherapy and CSI was safe and effective for patients with intracranial NGGCTs. Radiotherapy should be used with caution for patients < 11.5 years due to growth impairment.

Dose to neuroanatomical structures surrounding pituitary adenomas and the effect of stereotactic radiosurgery on neuroendocrine function: an international multicenter study

OBJECTIVE

Stereotactic radiosurgery (SRS) provides a safe and effective therapeutic modality for patients with pituitary adenomas. The mechanism of delayed endocrine deficits based on targeted radiation to the hypothalamic-pituitary axis remains unclear. Radiation to normal neuroendocrine structures likely plays a role in delayed hypopituitarism after SRS. In this multicenter study by the International Radiosurgery Research Foundation (IRRF), the authors aimed to evaluate radiation tolerance of structures surrounding pituitary adenomas and identify predictors of delayed hypopituitarism after SRS for these tumors.

METHODS

This is a retrospective review of patients with pituitary adenomas who underwent single-fraction SRS from 1997 to 2019 at 16 institutions within the IRRF. Dosimetric point measurements of 14 predefined neuroanatomical structures along the hypothalamus, pituitary stalk, and normal pituitary gland were made. Statistical analyses were performed to determine the impact of doses to critical structures on clinical, radiographic, and endocrine outcomes.

RESULTS

The study cohort comprised 521 pituitary adenomas treated with SRS. Tumor control was achieved in 93.9% of patients over a median follow-up period of 60.1 months, and 22.5% of patients developed new loss of pituitary function with a median treatment volume of 3.2 cm3. Median maximal radiosurgical doses to the hypothalamus, pituitary stalk, and normal pituitary gland were 1.4, 7.2, and 11.3 Gy, respectively. Nonfunctioning adenoma status, younger age, higher margin dose, and higher doses to the pituitary stalk and normal pituitary gland were independent predictors of new or worsening hypopituitarism. Neither the dose to the hypothalamus nor the ratio between doses to the pituitary stalk and gland were significant predictors. The threshold of the median dose to the pituitary stalk for new endocrinopathy was 10.7 Gy in a single fraction (OR 1.77, 95% CI 1.17-2.68, p = 0.006).

CONCLUSIONS

SRS for the treatment of pituitary adenomas affords a high tumor control rate with an acceptable risk of new or worsening endocrinopathy. This evaluation of point dosimetry to adjacent neuroanatomical structures revealed that doses to the pituitary stalk, with a threshold of 10.7 Gy, and doses to the normal gland significantly increased the risk of post-SRS hypopituitarism. In patients with preserved pre-SRS neuroendocrine function, limiting the dose to the pituitary stalk and gland while still delivering an optimal dose to the tumor appears prudent.

Examination of the Dose-Effect Relationship of Radiation-Induced Hypopituitarism: Results of a Case-Control Study

Purpose

Previous reports have documented a dose-effect relationship for radiation-induced hypopituitarism in patients receiving therapy near or at the base of the skull. We aimed to characterize this long-term endocrinopathy further by examining the effect of dose on both the incidence and severity of toxicity, as well as exploring a possible dose threshold for this effect.

Methods and Materials

Out of an initial 346 patients who had received radiation therapy to the base of the skull, 53 patients with adequate endocrine evaluation were found. Of these, 19 patients who subsequently developed at least 1 endocrinopathy (cases) as well as 17 patients who did not (controls) were identified, for a total of 36. Patients’ charts were reviewed, and endocrinologic laboratory tests recorded. Treatment plans were reviewed and doses to the hypothalamus and pituitary gland were calculated. One-way analysis of variance was used to determine differences between cases and controls, and Pearson's correlation coefficient was used to relate mean pituitary dose to serum free thyroxine, insulin-like growth factor 1, prolactin, cortisol, and luteinizing hormone.

Results

There were 20 men and 16 women, with a median age of 58. Median follow-up was 32 months (range, 18- 85 months). Median total plan dose delivered was 54 Gy (range, 50.4-70 Gy). Independent sample t tests as well as univariate analysis showed a significantly greater dose to the hypothalamus and pituitary of the cases compared with the controls, while other factors were not significantly different between the 2 groups. There was a statistically significant negative correlation (Pearson's correlation coefficient = -0.65, P = .001) between the mean dose to the pituitary gland and the serum free thyroxine. No case of endocrine toxicity was observed at a mean dose to the pituitary below 30 Gy.

Conclusions

Our results suggest that late endocrinopathy is a true deterministic effect, with a dose threshold, and with both the incidence and severity of toxicity being related to the dose.

Central diabetes insipidus induced by temozolomide: A report of two cases

INTRODUCTION

Central diabetes insipidus is a heterogeneous condition characterized by decreased release of antidiuretic hormone by the neurohypophysis resulting in a urine concentration deficit with variable degrees of polyuria. The most common causes include idiopathic diabetes insipidus, tumors or infiltrative diseases, neurosurgery and trauma. Temozolomide is an oral DNA-alkylating agent capable of crossing the blood-brain barrier and used as chemotherapy primarily to treat glioblastoma and other brain cancers.

CASES

Two men (aged 38 and 54 years) suddenly developed polyuria and polydispsia approximately four weeks after the initiation of temozolomide for a glioblastoma. Plasma and urine parameters demonstrated the presence of a urinary concentration defect.

MANAGEMENT

The clinical and laboratory abnormalities completely resolved with intranasal desmopressin therapy, allowing the continuation of temozolomide. The disorder did not relapse after cessation of temozolomide and desmopressin and relapsed in one patient after rechallenge with temozolomide.

DISCUSSION

Our report highlights the importance of a quick recognition of this exceptional complication, in order to initiate promptly treatment with desmopressin and to maintain therapy with temozolomide.

Thyroid Sequelae of Pediatric Cancer Therapy

The hypothalamic-pituitary-thyroid axis is a common site of unintended, acquired disease either during or after the treatment of cancer. Children treated with external radiation therapy are at the highest risk for developing a thyroid-related late effect, but thyroid dysfunction and second primary thyroid neoplasms can also occur after treatment with radiopharmaceutical agents such as 131I-metaiodobenzylguanidine. Increasingly recognized is the development of early thyroid dysfunction as an off-target consequence of the more novel cancer therapeutics such as the tyrosine kinase inhibitors and immune checkpoint inhibitors. Thyroid sequelae resulting from irradiation may manifest only after years to decades of follow-up, and their resultant clinical symptoms may be indolent and non-specific. Therefore, lifelong monitoring of the childhood cancer survivor at risk for thyroid disease is paramount. In this comprehensive review, the myriad thyroid adverse effects resulting from pediatric cancer treatment are discussed and an overview of screening and treatment of these thyroid sequelae provided.

Are hypothalamic- pituitary (HP) axis deficiencies after whole brain radiotherapy (WBRT) of relevance for adult cancer patients? - a systematic review of the literature

Background

Cranial radiotherapy (cRT) can induce hormonal deficiencies as a consequence of significant doses to the hypothalamic-pituitary (HP) axis. In contrast to profound endocrinological follow-up data from survivors of childhood cancer treated with cRT, little knowledge exists for adult cancer patients.

Methods

A systematic search of the literature was conducted using the PubMed database and the Cochrane library offering the basis for our debate of the relevance of HP axis impairment after cRT in adult cancer patients. Against the background of potential relevance for patients receiving whole brain radiotherapy (WBRT), a particular focus was set on the temporal onset of hypopituitarism and the radiation dose to the HP axis.

Results

Twenty-eight original papers with a total of 1728 patients met the inclusion criteria. Radiation doses to the HP area ranged from 4 to 97 Gray (Gy). Hypopituitarism incidences ranged from 20 to 93% for adult patients with nasopharyngeal cancer or non-pituitary brain tumors. No study focused particularly on hypopituitarism after WBRT. The onset of hypopituitarism occurred as early as within the first year following cRT (range: 3 months to 25.6 years). However, since most studies started follow-up evaluation only several years after cRT, early onset of hypopituitarism might have gone unnoticed.

Conclusion

Hypopituitarism occurs frequently after cRT in adult cancer patients. Despite the general conception that it develops only after several years, onset of endocrine sequelae can occur within the first year after cRT without a clear threshold. This finding is worth debating particularly in respect of treatment options for patients with brain metastases and favorable survival prognoses.

Endocrine Status in 29 Patients Treated by Curative Radiation Therapy for Nasopharyngeal Carcinoma

The basal endocrine status of 29 patients treated with curative radiation therapy for nasopharyngeal carcinoma was assessed; they were disease-free for a minimum of 4 years from the end of treatment. None showed clinical evidence of endocrine disease, and most of them had a substantially normal hormonal blood pattern. A slightly elevated TSH value, suggesting subclinical primary hypothyroidism, was found only in two male patients, which could be ascribed to the radiotherapeutic treatment of the neck. Although we cannot exclude more subtle alterations of hypothalamic-pituitary function, the percentage incidence of endocrine impairment in our patients seems lower than previously reported by other authors.

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.

Hypothalamic/pituitary morbidity in skull base pathology

In this article the epidemiology, pathophysiology, clinical presentation, investigation, management, and prognosis of hypopituitarism and hypothalamic dysfunction, arising from skull base pathologies and treatment of these conditions, are reviewed and discussed. The clinical question: "What is the consequence of pituitary hypofunction in young patients (ie, craniopharyngioma)?" is answered based on information provided in the review.

Pituitary dysfunction in adult patients after cranial radiotherapy: systematic review and meta-analysis

CONTEXT

Cranial radiotherapy is an important cause of hypopituitarism. The prevalence of hypopituitarism varies considerably between studies.

OBJECTIVE

We conducted a systematic review and meta-analysis of reported prevalences of hypopituitarism in adults radiated for nonpituitary tumors.

DATA SOURCES

We searched PubMed, EMBASE, Web of Science, and the Cochrane Library to identify potentially relevant studies.

STUDY SELECTION

Studies were eligible for inclusion with the following criteria: 1) cranial radiotherapy for nonpituitary tumors and/or total body irradiation for hematological malignancies; 2) adult population (>18 yr old); and 3) report on endocrine evaluation.

DATA EXTRACTION

Data review was done by two independent reviewers. Besides extraction of baseline and treatment characteristics, also endocrine tests, definitions, and cutoff values used to define pituitary insufficiency were extracted.

RESULTS

Eighteen studies with a total of 813 patients were included. These included 608 patients treated for nasopharyngeal cancer (75%) and 205 for intracerebral tumors. The total radiation dose ranged from 14 to 83 and 40 to 97 Gy for nasopharyngeal and intracerebral tumors, respectively. The point prevalence of any degree of hypopituitarism was 0.66 [95% confidence interval (CI), 0.55-0.76]. The prevalence of GH deficiency was 0.45 (95% CI, 0.33-0.57); of LH and FSH, 0.3 (95% CI, 0.23-0.37); of TSH, 0.25 (95% CI, 0.16-0.37); and of ACTH, 0.22 (95% CI, 0.15-0.3), respectively. The prevalence of hyperprolactinemia was 0.34 (95% CI, 0.15-0.6). There were no differences between the effects of radiotherapy for nasopharyngeal vs. for intracerebral tumors.

CONCLUSION

Hypopituitarism is prevalent in adult patients after cranial radiotherapy for nonpituitary tumors. Therefore, all patients treated by cranial radiotherapy should have structured periodical assessment of pituitary functions.

Hypogonadism in men with erectile dysfunction may be related to a host of chronic illnesses

The prevalence of hypogonadism has been found to be increased in certain chronic illnesses, especially diabetes, hypertension and obesity. Recently, the prevalence of hypogonadism in primary care practices mirrored that in our population of men with erectile dysfunction (ED). In this study, the prevalence of hypogonadism in nearly 1000 men with ED was tabulated, using a retrospective chart review, and analyzed for association with the various contributing medical and psychological factors. The prevalence of hypogonadism was determined in men with a variety of chronic illnesses, and was further characterized by decade. We observed an association between hypertension (P=0.025), tobacco abuse (P=0.0059), sleep apnea (P=0.0001), work stress (P=0.041) and hypogonadism. These data were further analyzed for the odds ratio and confidence interval (Forest plot), which showed strong association for sleep apnea and work stress. We did not observe any significant association between diabetes, atherosclerosis, alcohol abuse, multiple medications, asthma, seizure disorder, anxiety/depression and hypogonadism (P values for Cochran-Mantel-Haenszel general association were 0.48, 0.97, 0.25, 0.69, 0.22, 0.76 and 0.98, respectively). We suggest that a host of chronic illnesses have a high prevalence of secondary hypogonadism. Men who have chronic medical or psychological illnesses should have their testosterone level checked, especially when sexual dysfunction symptoms or signs are present.

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.

Pituitary deficiency after brain radiation therapy

Brain radiotherapy is a frequent and overlooked cause of pituitary deficiency in adults which may alter patients' health and quality of life. Hormonal consequences have been better studied in children. The onset of hormonal deficiencies depends on the dose delivered to the pituitary-hypothalamic region while their incidence and severity depends on dose fractionating and follow-up duration. Somatotrophic function is the first affected, 90% of patients being GH deficient 10 years after radiotherapy. Other anterior pituitary functions are affected later and less frequently. While initial damage occurs in the hypothalamus, accounting for mild hyperprolactinemia in 30-50% of cases, diabetes insipidus is never observed. Direct pituitary deficiency may occur later. Responses to ACTH or GHRH-arginine tests may be normal for several years though an ACTH and/or GH deficiency has been demonstrated by an insulin tolerance test, which is considered as the gold standard. When the cranio-spinal area--including the neck--has been irradiated, primary thyroid deficiency might occur. Repeated cervical ultrasonographic follow-up is mandatory to exclude radiation-induced thyroid cancer. The gonadotrophic function might be altered after small doses of irradiation causing precocious puberty, while at higher doses delayed puberty or true gonadotrophic deficiencies are more often observed. Combined radio- and chemotherapy might result in mixed central and peripheral deficiencies that might be difficult to diagnose. When radiotherapy is performed in adulthood, GH deficiency is less common, although the sequence of hormonal deficiencies is similar to that observed in children. Prospective longitudinal studies are required to determine the time course and sequence of onset of each deficiency, in order to tailor the monitoring of these patients to their specific needs.

Sensitivity of anterior pituitary hormones to irradiation

Cranial irradiation is used in the management of a diverse group of intracranial pathologies. However, if any part of the hypothalamic-pituitary axis is included in the radiation field, there is a risk of developing neuroendocrine dysfunction. Growth hormone is the most radiosensitive of the anterior pituitary hormones, followed by the gonadotropins, adrenocorticotropic hormone and thyroid-stimulating hormone. A number of factors determine both the occurrence and severity of hypothalamic-pituitary dysfunction, including: the dose of radiation received by the hypothalamic-pituitary axis (determined by a number of factors including total dose and fractionation schedule and ultimately expressed as the biological effective dose); length of time since cranial irradiation; age of the patient at the time of cranial irradiation; type of radiotherapy administered; and the different inherent radiosensitivities of the anterior pituitary hormones. These neuroendocrine abnormalities usually develop a number of years after the initial insult and, therefore, patients who have received cranial irradiation should receive annual endocrine assessments. The establishment of endocrine late-effect clinics for the survivors of childhood cancers have gone some way to addressing this problem; however, other groups of patients, particularly those receiving cranial irradiation in adult life, may not have systematic endocrine assessment.

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.

Target Gland Dysfunction Following External Cranial Radiation for Extrasellar Tumours

BACKGROUND

Diseases of the pituitary gland manifest as increased or decreased production of one or more of these hormones that in turn trigger a series of secondary hormonal changes in target glands (Thyroid, Adrenal and Gonad). Dysfunction of target glands may follow treatment with external radiation when hypothalamo-pituitary axis lies within the field of radiation. The present study has been undertaken with the aim to study target gland dysfunction and their relationship with dose of radiotherapy and duration after radiotherapy in patients who have received extracranial radiation for extrasellar tumours.

METHODS

In this study, 96 patients who underwent cranial radiation 12 months ago were evaluated. Basal 8 am venous blood samples were taken for estimation of triiodothyronine (T3), thyroxin (T4), thyrotropin stimulating hormone (TSH) and basal cortisol estimation. Pooled samples (three samples taken 20 minutes apart and pooled together) were taken for LH, FSH and testosterone (TE) estimation. Insulin tolerance test was performed for stimulated cortisol levels.

RESULTS

Target gland dysfunction was present in 72 (75%) patients. Hypogonadism was present in 48 (53%) of post-pubertal patients. 36% of male patients had hypogonadism whereas 100% of female patients had hypogonadism. Patients with hypogonadism were older, received higher doses of radiation and evaluated earlier after radiotherapy than without hypogonadism. Serum testosterone level declined significantly with increasing doses of radiation. Hypoadrenalism was present in 44 patients (46%). There was no significant difference of age, radiation dose and radiation fraction among patients with or without adrenal insufficiency. Proportion of patients with hypoadrenalism increased with increasing duration after radiotherapy. Hypothyroidism was present in 12 patients (13%). Proportion of patients with hypothyroidism doubled with increasing dose of radiation. Serum T3 level declined significantly with increasing doses of radiation. Patients with hypothyroidism had significantly low T3 and T4 level, but significantly higher TSH and basal and peak cortisol levels than patients without hypothyroidism.

CONCLUSION

Target gland dysfunction is common after extracranial radiation for extrasellar tumours. Hypogonadism was the commonest followed by hypoadrenalism and hypothyroidism. Target gland dysfunction was related to age, radiation dose and duration after radiotherapy, but not with fraction of radiation.

Growth Hormone and Prolactin Secretion after External Cranial Irradiation for Extrasellar Tumours

BACKGROUND

Deficiency of one or more anterior pituitary hormones may follow treatment with external radiation when hypothalamo-pituitary axis lies within the field of radiation. Patients with brain tumours who are treated with radiation frequently have growth hormone (GH) deficiency, other neuro-endocrine abnormalities are presumed to be uncommon. The present study has been undertaken with the aim to study GH and prolactin secretion, their relationship with dose of radiotherapy and duration after radiotherapy in patients who have received extracranial radiation for extrasellar tumours.

METHOD

In this study, 96 patients who underwent cranial radiation before 12 months, were evaluated. Basal 8 a.m. venous blood samples were taken for estimation of prolactin and GH. Insulin tolerance test was performed for stimulated GH levels.

RESULT

GH deficiency was present in 59% patients. Isolated GH deficiency was present in 12 (21%) cases, whereas others had associated hormone deficiency. Height percentiles of prepubertal and pubertal patients were 10(th) to 25(th) (-1.5 to -0.5SD). Patients with isolated GH deficiency had received significantly higher radiation dose than normal pituitary function (5795 ± 24 vs 4908 ± 71, p=0.001). Proportion of patients with GH deficiency increased with increasing dose of radiation (p=0.12), fractional dose of radiation (p=0.08) and increasing duration after radiotherapy (p=0.038). GH levels among all decreased significantly with increasing dose of radiation (p=0.02). Hyperprolactinemia was present in 21% of cases. GH deficiency is more common with lower (<5ng/ml) and higher (>15ng/ml) prolactin levels.

CONCLUSION

GH deficiency is common after extracranial radiation for extrasellar tumours. GH deficiency is related to dose of radiation, fraction of radiation, and duration after radiotherapy. All prepubertal and pubertal patients with GH deficiency had their height percentile within normal range. Relation of prolactin and GH deficiency indicates that radiation affects both hypothalamus and pituitary.

Effects of gamma knife radiosurgery of pituitary adenomas on pituitary function

Object. The authors undertook a retrospective analysis of the incidence and time course of pituitary insufficiency following gamma knife radiosurgery (GKS) for pituitary adenomas.

Methods. Pituitary adenomas in 92 patients were analyzed. There were 61 hormonally inactive tumors, 18 prolactinomas, and nine somatotropic and four adrenocorticotropic adenomas. The mean tumor volume was 3.8 cm3 (range 0.2–14.6 cm3). The mean prescription dose was 15 Gy. The mean prescription isodose was 50.7%.

The mean follow-up time was 4.6 years (range 1.2–10 years). The following new or deteriorating insufficiencies that did not require treatment were recorded for the different pituitary axes: follicle-stimulating hormone (FSH)/luteinizing hormone (LH) 19 (20.6%), thyroid-stimulating hormone (TSH) 32 (34.8%), adenocorticotropic hormone (ACTH) 10 (10.9%), and growth hormone (GH) 26 (28.3%). For new insufficiencies or deterioration requiring replacement therapy, the figures were as follows: FSH/LH 20 (21.7%), TSH 22 (23.9%), ACTH eight (8.7%), and GH 12 (13%). Spot dosimetry was performed in 59 patients in the hypothalamic region, the pituitary gland, and pituitary stalk. The pituitary stalks in patients with deterioration of pituitary function received a statistically higher dosage of radiation, 7.7 ± 3.7 Gy compared with 5.5 ± 3 Gy (p = 0.03).

Conclusions. The function of the residual normal pituitary gland is less affected following GKS of pituitary adenomas than after fractionated radiotherapy. Nonetheless, increased attention needs to be exercised to reduce the dose to the stalk and pituitary gland to minimize the incidence of these complications.

Lack of menstrual cycle effects on hypothalamic-pituitary-adrenal axis response to insulin-induced hypoglycaemia

OBJECTIVE

Limited data are available on the effects of the menstrual cycle on the hypothalamic-pituitary-adrenal axis (HPA) function. This study evaluates HPA axis reactivity to insulin-induced hypoglycaemia over the menstrual cycle.

PATIENTS

Twelve normal women were randomized to placebo and evaluated during three successive menstrual cycles. Menstrual phase was documented by menstrual diary and by oestradiol and progesterone levels at the time of each insulin tolerance test (ITT). Six normal men were included as a comparison in the statistical analysis.

MEASUREMENTS

Afternoon ITTs were performed initially on the second or third day of menses in women, then seven more ITTs followed at one or two week intervals during the next 10 weeks. Serum measurements of glucose, adrenocorticotrophin (ACTH) and cortisol were obtained.

RESULTS

The glucose and ACTH responses to the ITTs were similar between men and women. Cortisol levels at baseline and during the test were higher in men than in women, although the amount of change was similar. Glucose, ACTH and cortisol response to insulin-induced hypoglycaemia did not vary over the menstrual cycle or during repeat testing in men or women.

CONCLUSIONS

These data show that it is unnecessary to control for menstrual cycle during insulin tolerance tests performed at 1600 hours. It is, however, necessary to control for the effect of sex on cortisol levels. Repeat testing more than one week apart does not appear to influence the glucose, ACTH or cortisol response to insulin stress.

Endocrine dysfunctions in patients treated for brain tumors: incidence and guidelines for management

Endocrine alterations are frequently found in patients undergoing treatment for CNS tumors. Careful follow-up aimed at the early detection of recurrences, with life-long monitor of hypothalamus-pituitary (HP) function, will also reveal any endocrine dysfunctions; indeed, their appropriate diagnosis and treatment may determine a significant improvement in the quality of life of these patients.

Stereotactic radiosurgery for recurrent surgically treated acromegaly: comparison with fractionated radiotherapy

OBJECT

The authors tested the assumption that gamma knife radiosurgery is more effective than fractionated radiotherapy for the treatment of patients with acromegaly who have undergone unsuccessful resective surgery. Untreated and uncured acromegaly causes illness and death. Acromegalic patients in whom growth hormone and, particularly, insulin-like growth factor I are not normalized must undergo further treatment.

METHODS

After unsuccessful operations, 16 patients suffering from recurrent and uncured acromegaly underwent stereotactic radiosurgery (25 Gy to the tumor margin, 50 Gy maximum), the outcome of which was compared with the result obtained in 50 patients who received fractionated radiotherapy (40 Gy). The cumulative distribution functions of the two groups (Kaplan-Meier estimate) differed significantly (p < 0.0001 in the log-rank test of Mantel). The mean time to simultaneous normalization of both parameters was 1.4 years in the group treated with the gamma knife and 7.1 years in the group treated with fractionated radiotherapy.

CONCLUSIONS

The authors suggest the use of stereotactic radiosurgery as the preferred treatment for recurrent acromegaly resulting from unsuccessfully resected tumors.

A comparison of pituitary-adrenal responses to corticotropin-releasing hormone, hypoglycaemia and metyrapone in children with brain tumours and growth hormone deficiency

To assess hypothalamic-pituitary function, a corticotropin-releasing hormone (CRH) stimulation test was performed in nine children following treatment for brain tumours and in 27 growth hormone deficient (GHD) children whose pituitary adrenocorticotropin (ACTH) secretion was normal. In both groups, CRH tests were compared with ACTH and cortisol responses to insulin-induced hypoglycaemia and with ACTH response to metyrapone stimulation. In the patients with brain tumours (five craniopharyngiomas, two suprasellar germinomas, one cerebellar medulloblastoma and one cerebellar ependymoma), ACTH responses to CRH varied greatly with absent or blunted, normal, and exaggerated reactions. Cortisol and ACTH responses were not always correlated. In GHD children but not in children with brain tumours the responses to CRH, insulin tolerance test and metyrapone test were correlated. The marked variability of the CRH test was possibly caused by compounding factors such as preceding corticosteroid therapy, concomitant desmopressin therapy and spontaneous regeneration of damaged brain structures

CONCLUSION

Interpretation of the CRH test to assess hypothalamic-pituitary function in patients with brain tumours is difficult due to compounding factors. Many patients require prolonged follow up with repeated endocrinological evaluation.

A prospective study of hypothalamus pituitary function after cranial irradiation with or without radiosensitizing chemotherapy

Hypopituitarism can occur after cranial irradiation. Combined chemotherapy (CT) and radiotherapy (RT) have greatly improved the survival of patients with nasopharyngeal carcinoma (NPC). We studied 37 NPC patients who received RT and/or CT prospectively to determine if combined CT worsens the radiation damage. Patients were studied before, 6 months, 1 year and 2 years after treatment, with 4 combined hypothalamic releasing hormones stimulation test and insulin hypoglycemic test. Five developed hypothyroidism and 3 developed hyperprolactinemia after treatment. The TSH response to TRH progressively increased. In male patients who received RT only, the LH response to GnRH was reduced after RT. The FSH response to GnRH increased 6 months and 1 year after RT, and returned to pretreatment level 2 years after RT. In male patients who received RT and CT, after an initial rise 6 months after treatment, both FSH and LH responses to GnRH declined. The ACTH response to ovine CRH was decreased 6 months after RT and remained so later on, while the cortisol response became prolonged and enhanced progressively after RT. The peak GH response to GRH increased significantly 1 year after RT in patients who also received CT. The GH response to insulin hypoglycemia was also increased after RT while the cortisol response remained the same. In conclusion, cranial irradiation caused a progressive impairment of the hypothalamus-pituitary-endocrine axes. Combined CT may mask the radiation damage to GnRH neuron by inducing primary hypogonadism. There may be hippocampal damage in addition to hypothalamo-pituitary damage after cranial irradiation.

Radiation and neuroregulatory control of growth hormone secretion

OBJECTIVE

Cranial irradiation frequently results in growth hormone (GH) deficiency. Patients with radiation-induced GH deficiency usually remain responsive to exogenous growth hormone releasing hormone, implying radiation damages the hypothalamus rather than the pituitary. Little is known about the effect of cranial irradiation on the neuroendocrine control of GH secretion. This study was to determine the effect of cranial irradiation on somatostatin tone.

DESIGN

Somatostatin tone was examined by manipulating cholinergic tone in young adults with radiation-induced GH deficiency and a control population. Each individual underwent three separate studies: the GH response to 100 micrograms GHRH-(1-29)-NH2 was assessed alone, and 60 minutes after pyridostigmine or pirenzepine.

PATIENTS

Eight young male adults with radiation induced GH deficiency following treatment in childhood for a brain tumour or acute lymphoblastic leukaemia, and ten healthy adult men were studied.

MEASUREMENTS

Serum growth hormone was measured at 15-minute intervals throughout each of the three study periods.

RESULTS

One of 10 controls and four of eight irradiated subjects had a peak GH level to GHRH analogue of less than 20 mU/l. After pretreatment with pyridostigmine, all subjects except one irradiated subject had a peak GH level of greater than 20 mU/l. Pretreatment with pyridostigmine and pirenzepine significantly modified the GH response to GHRH analogue within both groups (P < 0.0005). Pretreatment with pyridostigmine significantly enhanced the GH response to GHRH analogue (median (range) area under the curve, 9029 (1956-20940) mU/l/min in controls vs 1970 (628-3608) mU/l/min in the irradiated group) compared with GHRH analogue alone (1953 (512-16140) mU/l/min in control group vs 997 (266-3488) mU/l/min in the irradiated group). Pretreatment with pirenzepine significantly attenuated the GH response to GHRH analogue (552 (64-1274) mU/l/min in controls vs 305 (134-2726) mU/l/min in irradiated group). Between the groups there was no significant difference in GH area under the curve (AUC) after GHRH analogue alone. There was a significantly (P = 0.0014) greater increment of GH secretion after pyridostigmine and GHRH analogue compared with GHRH analogue alone (difference in AUC of pyridostigmine+GHRH analogue and GHRH analogue alone 6348 (696-12856) mU/l controls vs 542 (120-1340) mU/l in the irradiated group) and significantly (P = 0.033) greater suppression of GH secretion after pirenzepine and GHRH analogue compared with GHRH analogue alone (difference in AUC of GHRH analogue alone and pirenzepine+GHRH analogue 1644 (222-15205) mU/l in controls vs 479 (469-1623) mU/l in the irradiated group) in the control population compared with those who had received cranial irradiation in childhood.

CONCLUSIONS

These data suggest that cranial irradiation reduces but does not abolish somatostatin (SRIH) tone and also reduces endogenous GHRH secretion. Although SRIH tone is reduced, it can be increased by cholinergic manipulation and is therefore not irreversibly fixed. This has possible implications if GHRH analogues were used to treat children with radiation induced GH deficiency.

Pulsatile gonadotrophin-releasing hormone therapy in patients with pituitary tumours treated by surgery and irradiation

OBJECTIVE

Pulsatile administration of GnRH for induction of ovulation is effective for women with idiopathic hypogonadotrophic hypogonadism. We were interested to assess the pituitary-ovarian response to pulsatile GnRH infusion and the therapeutic effectiveness of restoring ovulation in a group of hypogonadotrophic women previously treated with surgery and irradiation to pituitary tumours.

PATIENTS

The group of patients comprised 15 hypogonadotrophic women, aged 29-40 years (mean 32.4 years), who had undergone transsphenoidal adenomectomy or craniotomy and irradiation with a total of 4500-5400 cGy in 25 fractional doses divided over 5-6 weeks. The time interval from irradiation to study was 6.3 +/- 2.0 years (mean +/- SD).

TREATMENT

A single bolus GnRH (100 micrograms) test and pulsatile infusion of GnRH were performed to assess the pituitary gonadotrophin reserve and induce ovulation. We tried to correlate the pituitary response with characteristics of intracranial lesions on computerized tomography findings. We undertook ovarian biopsy in one patient who failed to respond to gonadotrophin therapy and pulsatile infusion of GnRH.

RESULTS

Twelve women (80%) showed evidence of ovulation in response to pulsatile GnRH treatment and five subsequently became pregnant. Four of 12 ovulators were previous non-ovulators to exogenous gonadotrophin therapy. There was no correlation between pituitary response and character of lesions based on computerized tomography findings. A patient who failed to respond to either gonadotrophin or pulsatile infusion of GnRH had premature ovarian failure on ovarian histology.

CONCLUSIONS

The functional reserve capacity of pituitary gonadotrophs may remain less impaired by tumour encroachment, pituitary surgery or irradiation than had previously been thought. This holds promise for ovulation induction in hypogonadotrophic patients who had been treated with surgery and irradiation for pituitary tumours.

Pituitary gland emergencies

Emergencies in pituitary disease are not common. They can result from the failure of the pituitary gland to secrete one or more pituitary hormones, or from neuro-ophthalmological symptoms due to the mass effect of an expanding hypothalamic-pituitary tumour. Loss of hormone secretion, particularly ACTH and, to a lesser extent, TSH, can rapidly become life-threatening and requires urgent replacement therapy. Acute severe hypopituitarism should be vigorously treated as an emergency with a glucocorticoid preparation. Neuro-ophthalmological symptoms such as visual impairment, sudden onset of severe headache and alteration of the level of consciousness should prompt appropriate radiological investigations, since this may well call for emergency surgery.

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.

Adjuvant chemotherapy for advanced nasopharyngeal carcinoma in childhood

Seven children with advanced nasopharyngeal carcinoma younger than 20 years of age diagnosed between 1975 and 1986 (inclusive) were treated with a uniform adjuvant chemotherapy regimen, which consisted of vincristine (1.5 mg/m2; day 1), doxorubicin (45 mg/m2; day 1), 5-fluorouracil (8 mg/kg; days 1 through 5), and cyclophosphamide (7 mg/kg; days 1 through 5). This combination chemotherapy was given for 12 to 24 months after completion of radiation therapy. The radiation doses to the primary sites ranged from 6000 cGy to a maximum of 6800 cGy. The radiation doses for neck prophylaxis ranged from 4500 cGy to a total of 5000 cGy. Involved sites were irradiated to at least an additional boost of 1000 cGy. One patient had an external dose 6000 cGy to the primary site boosted with brachytherapy of 3000 cGy at the surface of an ovoid. After chemotherapy myelosuppression occurred in all patients and was tolerable. All seven patients are surviving, six disease-free, for 22 months to 12 years (median, 4 years). This study suggests that the combination of radiation therapy and chemotherapy as used here has acceptable toxicity and is effective and further suggests that children with nasopharyngeal carcinoma, even in its advanced stage at diagnosis, may be curable.

Growth hormone response to growth hormone-releasing hormone (hp GHRH1-44) as an index of growth hormone secretory dysfunction after prophylactic cranial irradiation for acute lymphoblastic leukemia (24 grays)

The growth hormone response to growth hormone releasing hormone hp GHRH1-44 (2 micrograms/kg i.v.) was studied in 19 prepubertal children who had been irradiated with 24 Gy for acute lymphoblastic leukemia (ALL) or lymphosarcoma (LS) at a mean chronological age of 4 10/12 years (limits 10/12 to 9 years). They were evaluated after a mean time interval of 4 8/12 +/- 3/12 years and compared to 14 prepubertal children with constitutional short stature (CSS). The individual responses to GHRH were decreased in all but three of the irradiated children. The mean GH response was 16.7 +/- 2.5 ng/ml as compared to 52.6 +/- 8.5 ng/ml in the control group (p less than 0.001). The GH response to GHRH was not correlated with the GH response to arginine-insulin tolerance test (AITT). A decreased response to GHRH with values between 12.5 and 19.4 ng/ml was observed in four cases with normal growth rates and normal GH responses to AITT. These results suggest that an impaired GH response to GHRH is a frequent finding after cranial irradiation for ALL or LS and may be the only sign of GH secretory dysfunction. It is probably indicative of early hypothalamic impairment of GH secretion.

Endocrine function following high dose proton therapy for tumors of the upper clivus

The endocrine status of patients receiving proton radiation for tumors of the upper clivus was reviewed to evaluate the effect of high dose treatment on the pituitary gland. The fourteen patients had chordomas or low grade chondrosarcomas and were all treated by the same techniques. The median tumor dose was 69.7 Cobalt Gray Equivalent (CGE) with a range from 66.6 to 74.4 CGE. (CGE is used because modulated protons have an RBE of 1.1 compared to 60Co). The daily fraction size was 1.8-2.1 CGE. The median follow-up time is 48 months, ranging from 30 to 68 months. All treatments were planned using a computerized multi-dimensional system with the position of the pituitary outlined on the planning CT scan. Review of the dose distribution indicated that the dose to the pituitary ranged from 60.5 to 72.3 CGE, with a median of 67.6 CGE. One female patient had decreased thyroid and gonadotropin function at the time of diagnosis and has been on hormone replacement since that time. The other three females were all pre-menopausal at the time of radiotherapy. At this time four patients (3 males and 1 female) have developed endocrine abnormalities 14 to 45 months after irradiation. All four had evidence of hypothyroidism and two have also developed corticotropin deficiency. The three males had decreased testosterone levels; the female patient developed amenorrhea and hyperprolactinemia. All four are asymptomatic with ongoing hormone replacement.