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Biomedical subjects

C G Beardwell

Publications and source records attributed to C G Beardwell.

At least 19 recordsLinked to original sources
PubMed1991

The effect of external pituitary irradiation on elevated serum prolactin levels in patients with pituitary macroadenomas.

The response of serum prolactin to external radiotherapy was studied in 58 patients (32 women) with pituitary tumours, aged between 16 and 75 years. Forty-four patients underwent pituitary surgery before radiotherapy. Six patients were irradiated with a regimen of 20 Gy in eight fractions over 10-11 days and the remainder received 35-42.5 Gy in 15 fractions over 20-22 days. Following radiotherapy, 44 patients received additional treatment with dopaminergic agonists. Prolactin levels ranged from 1078 to 491,000 mU/l (median 11,750 mU/l) before radiotherapy and all but three patients showed a fall in serum prolactin (measured 4 weeks after stopping bromocriptine in those on dopamine agonist therapy) during observation over periods of up to 154 months. All patients had evidence of pituitary fossa erosion or expansion at presentation and large tumours (Hardy-Vezina Grade 3-4) were more common in male patients (chi 2 = 10.08, p less than 0.01). The rate of fall of serum prolactin levels was greater in patients with true prolactin-secreting tumours when compared with those who had stalk or hypothalamic damage (p less than 0.005). The rate of decline of serum prolactin was also significantly related to the pre-radiotherapy value (rho = 0.519, p less than 0.01). A serum prolactin level less than 500 mU/l was achieved in 31 out of 44 patients treated with radiotherapy and dopaminergic agonist but only nine remained normoprolactinaemic when medication was discontinued for 4 weeks or more. The serum prolactin level fell permanently to less than 500 mU/l in two of 14 patients treated with radiotherapy only. Actuarial analysis of data from all patients indicated a 50 per cent probability that prolactin would be reduced to less than 500 mU/l by 10 years; this increased to 58 per cent for patients with smaller tumours (Hardy-Vezina grade 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗
PubMed1990

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.

Dose-Response Relationship, Radiation↗
PubMed1990

Low-dose pituitary irradiation for acromegaly.

External radiotherapy has been used as primary treatment for acromegaly in 29 patients and in combination with surgery in 41 patients in whom growth hormone levels remained elevated postoperatively. Fourteen further patients who did not receive radiotherapy have also been studied, four of whom had undergone surgical treatment. Radiotherapy schedules consisted of 20 Gy in eight fractions over 11 days (n = 23) or 35-40 Gy in 15 fractions over 21 days (n = 47). Growth hormone hypersecretion was either unchanged or increased with time in non-irradiated patients. In those patients who underwent radiotherapy, the likelihood of the mean GH level during GTT falling to less than 5 mU/l was unaffected by the total dose of radiation administered. However, patients with a pre-radiotherapy GH level of less than 30 mU/l showed a significantly increased probability of achieving a post- radiotherapy GH level less than 5 mU/l (P = 0.002). Previous surgery, initial serum prolactin and the age or sex of the patient did not predict the successful outcome of radiotherapy. In view of the known dose dependency of radiation-induced hypopituitarism, lower radiation dose schedules (20 Gy; eight fractions in 11 days) can be used in acromegaly with some benefit, especially in younger patients. However, all patients should undergo operative removal of as much GH-secreting tissue as possible, in order to lower GH levels and increase the probability of achieving a cure following radiotherapy.

Acromegaly↗
PubMed1990

Long-term follow-up of low-dose external pituitary irradiation for Cushing's disease.

Twenty-four patients (three male) with Cushing's disease, aged between 11 and 67 years, were treated with low-dose external pituitary irradiation (20 Gy in eight fractions over 10-12 days) and followed for between 13 and 171 months (median 93 months). Eleven patients (46%) went into remission 4-36 months after irradiation, but five subsequently relapsed. Two of these received no further active treatment, one underwent successful pituitary surgery, one underwent a second course of low-dose external irradiation (as yet unsuccessful) and one has been treated with metyrapone for a total of 75 months. One of the 13 patients who did not respond received a further course of low-dose pituitary irradiation with prompt remission and two have received metyrapone for 41 months and 15 years without ill effect. One patient died from cerebrovascular disease. The remaining nine patients underwent bilateral adrenalectomy (one after unsuccessful pituitary surgery) with rapid resolution of hypercortisolism. Five of these patients have developed hyperpigmentation and elevated ACTH levels (range 505-1150 ng/l). A pituitary microadenoma has been demonstrated on CT scan in three and successfully removed by microadenomectomy. In the present series, the low incidence of radiation-induced hypopituitarism and absence of other complications attributable to radiotherapy suggest that low-dose pituitary irradiation may be a useful treatment option in selected patients. However, long-term follow-up has demonstrated a high relapse rate and failure to prevent Nelson's syndrome in adrenalectomized patients, indicating that it should not be used as primary treatment in preference to selective adenomectomy.

Adolescent↗
PubMed1989

Radiation-induced hypopituitarism is dose-dependent.

Radiation-induced hypopituitarism has been studied prospectively for up to 12 years in 251 adult patients treated for pituitary disease with external radiotherapy, ranging in dose from 20 Gy in eight fractions over 11 days to 45 Gy in 15 fractions over 21 days. Ten further patients were studied 2-4 years after whole-body irradiation for haematological malignancies using 12 Gy in six fractions over 3 days and seven patients were studied 3-11 years after whole-brain radiotherapy for a primary brain tumour (30 Gy, eight fractions, 11 days). Five years after treatment, patients who received 20 Gy had an incidence of TSH deficiency of 9% and in patients treated with 35-37 Gy, 40 Gy and 42-45 Gy, the incidence of TSH deficiency (22, 35 and 52% respectively) increased significantly (P less than 0.001) with increasing dose. A similar relationship was observed for both ACTH and gonadotrophin deficiencies when the 20 Gy group was compared to patients treated with 35-45 Gy (P less than 0.01 and P less than 0.05 respectively). Growth hormone deficiency was universal by 5 years over the dose range 35-45 Gy. In seven patients who were treated with 30 Gy in eight fractions over 11 days, deficiencies were observed at a similar frequency to the 40 Gy group (15 fractions, 21 days). No evidence of pituitary dysfunction was detected in the ten patients who received 12 Gy (six fractions, 3 days). Both total radiation dose and fractionation schedule may determine the incidence of pituitary hormone deficiencies. The dose below which deficiencies do not occur is probably irrelevant to therapeutic irradiation of pituitary and other intracranial neoplasms.

Adolescent↗
PubMed1989

Hypopituitarism following external radiotherapy for pituitary tumours in adults.

The development of anterior pituitary hormone deficiencies has been studied in a group of 165 patients who underwent external radiotherapy for tumours of the pituitary or closely related anatomical sites, and who have been observed for up to 10 years. One hundred and forty had undergone pituitary surgery before radiotherapy. All patients received external radiotherapy by a three-field technique, giving 3750-4250 cGy in 15 or 16 fractions over 20-22 days. A combined test of anterior pituitary function using insulin hypoglycaemia or glucagon stimulation in conjunction with thyrotrophin and gonadotrophin releasing hormone tests and basal estimations of prolactin, thyroid hormones and testosterone or oestradiol was performed before radiotherapy. This was repeated six and 12 months later and subsequently annually. Before radiotherapy, 18 per cent of patients had normal growth hormone secretion, 21 per cent had normal gonadotrophin secretion, 57 per cent had normal corticotrophin reserve and 80 per cent had normal thyrotrophin secretion. Life table analysis demonstrated increasing incidences of all anterior pituitary hormone deficiencies with time: by five years all patients were growth hormone deficient, 91 per cent were gonadotrophin deficient, 77 per cent were corticotrophin deficient and 42 per cent were thyrotrophin deficient. At eight years, respective incidences of deficiencies were 100, 96, 84 and 49 per cent. Radiation-induced hyperprolactinaemia was seen in 73 patients; mean serum prolactin concentration rose from 227 +/- 11 mU/l to a peak of 369 +/- 60 mU/l at two years and subsequently declined towards the basal value. The primary diagnosis, patient age, sex, irradiated tissue volume and previous surgery were examined as variables that might influence the rate of development of anterior pituitary hormone deficiencies, but none of these factors had a significant effect. The radiation induced hyperprolactinaemia was however more marked in female patients. Although anterior pituitary hormone deficiencies most commonly developed in the order growth hormone, gonadotrophin, corticotrophin, thyrotrophin (61 per cent of patients), other sequences were evident. Most notably corticotrophin deficiency occurred before gonadotrophin deficiency. There is a high incidence of anterior pituitary hormone deficiencies in patients treated surgically for pituitary tumours and the incidence increases after external radiotherapy. Deficiencies may occur in an unpredictable sequence and endocrine testing is recommended on an annual basis.

Adolescent↗
PubMed1979

Normal growth despite abnormalities of growth hormone secretion in children treated for acute leukemia.

We have studied the relationship between abnormalities of the growth hormone-somatomedin axis and growth in 26 children previously treated for acute lymphatic leukemia. Each child had previously received cranial irradiation, was in complete clinical and hematologic remission, and off all drugs. The mean standing height SDS of the 26 children was significantly less than normal. There was no significant difference between the mean standing height SDS, height velocity SDS, somatomedin activities, and degree of bone age retardation between the 17 children who received the higher dose of cranial irradiation (Group 1) and the nine who had the lower dose of cranial irradiation (Group II). Furthermore, there was no significant reduction in mean height velocity SDS, somatomedin activity, or bone age in either group when compared to normal age-matched controls. The peak GH responses to both insulin hypoglycemia and an arginine test were significantly lowered in Groups I and II when compared to a control group of children. We conclude that only a minority of children, who previously received cranial irradiation for ALL were clinically GH deficient and, therefore, likely to benefit from GH therapy despite the finding that the majority of these children had reduced GH responses to pharmacologic stimuli.

Age Determination by Skeleton↗
PubMed1979

Acromegaly due to production of a growth hormone releasing factor by a bronchial carcinoid tumor.

We have studied growth hormone production in a patient with a bronchial carcinoid and acromegaly. The absence of growth hormone from the carcinoid tumour was demonstrated by extraction, cell culture and immunoperosidase techniques. Using a linked perfusion culture system, effluent from the bronchial carcinoid tumour culture stimulated a rapid release of growth hormone from a rat pituitary monolayer. This is the first time evidence of growth hormone releasing activity by a bronchial carcinoid has been demonstrated in a production.

Acromegaly↗
PubMed1979

Radiation-induced hyperprolactinaemia in a treated acromegalic.

A 31-year-old acromegalic was normoprolactinaemic after partial removal of her pituitary tumour. The post-operative external pituitary irradiation lowered the mean growth hormone (GH) level from 75 mU/1 to less than 1 mU/1 within 2 years. However, at the same time hyperprolactinaemia developed. These changes in the GH and prolactin levels were confirmed 3 and 4 years after irradiation. The cause of the hyperprolactinaemia was radiation-induced hypothalamic damage. Therefore it is suggested that similar damage may occur in patients receiving external pituitary irradiation for 'prolactinomas' and that this mechanism may contribute to the persistent hyperprolactinaemia observed in such patients.

Acromegaly↗
PubMed1978

Testicular function following irradiation of the human prepubertal testis.

Testicular function was studied in ten men, aged between 17 and 36 years, who had received irradiation for a nephroblastoma during childhood. The dose of scattered irradiation to the testes ranged from 268 to 983 rad. Eight subjects had either oligo- or azoospermia (0 to 5.6 million/ml), seven of whom had an elevated serum follicle-stimulating hormone (FSH) level. One subject showed evidence of Leydig cell dysfunction with a raised serum luteinizing hormone level (LH) and a low plasma testosterone concentration. A second group of eight prepubertal males, aged between 8 and 14 years, were studied. These had also been irradiated for abdominal malignancies during childhood and received a similar dose of irradiation to the testis as the first group studied. The plasma testosterone levels were within the normal range for prepubertal boys in all eight. The mean gonadotrophin levels were not significantly different from the mean levels of normal prepubertal males. Thus irradiation-induced damage to the germinal epithelium in prepubertal boys produces raised FSH levels after puberty but not before it. We conclude, therefore, that inhibition has a minor role in the control of the prepubertal hypothalamic-pituitary testicular axis and its contribution to gonadal control of gonadotrophin secretion changes with sexual maturation.

Adolescent↗