Hydrocortisone replacement therapy in children and adolescents with hypopituitarism

OBJECTIVE

Appropriate replacement doses of glucocorticoid are important to determine in primary and secondary adrenal deficiency in children, both to avoid the risks of hypoglycaemia and adrenal crisis associated with undertreatment, and to avoid growth suppression and reduced final height potential associated with steroid excess. The aim of this study was to assess how closely conventional twice daily hydrocortisone administration mimics physiological cortisol secretion in a group of ACTH-deficient children and adolescents.

PATIENTS

Fifty children and adolescents (aged 3-20 years) were studied who had had surgery +/- radiotherapy to the hypothalamopituitary region for removal of a craniopharyngioma. The patients were subdivided into two groups: group I comprised 44 patients known to be ACTH deficient (as determined by glucagon or insulin provocation tests of anterior pituitary function performed after surgery) and maintained on twice daily oral hydrocortisone replacement; group II comprised six patients known to be ACTH sufficient at their last assessment of pituitary function and not on hydrocortisone replacement. A third group of 10 boys (aged 7-13 years) who had no known endocrinopathy were used as controls (group III).

MEASUREMENTS

After intravenous cannula insertion, blood samples were taken every 2h for measurement of plasma cortisol and glucose over a period of 24h. Patients in group I continued on their usual doses of hydrocortisone, prescribed at 0800 and 1800 h.

RESULTS

The mean total daily replacement dose of hydrocortisone for patients in group I was 12.3 mg/m2/ day (range, 5.5-18.5). On the conventional twice daily dose regimen, there was a supraphysiological medium plasma cortisol level (629 nmol/l, range 185-1600; z = -3.76, P = 0.0002) 2 h after the morning dose relative to the control group, and a prolonged and unphysiological nadir from 1400-1800 h (median at 1600 h 42 nmol/l, range 13-1170; z = -3.13, P < 0.002) before the second dose of hydrocortisone was administered. Cortisol values were low, and often negligible, during the early hours of the morning (median at 0600 h 15 nmol/l, range 13-277, z = -4.87, P < 0.00001) and spontaneous hypoglycaemia was documented in one patient on a single 0800 h sample. One patient in group II was shown to be unequivocally cortisol deficient and median cortisol values for the remaining five suggested a suboptimal rise in plasma cortisol during the early hours of the morning.

CONCLUSION

Our cohort of patients provides an excellent model for the study of glucocorticoid replacement in cortisol-deficient children and adolescents and shows, as in adults, that the aim of mimicking the physiological nyctohemeral secretion of cortisol is difficult to achieve in practice and raises a number of important considerations unique to steroid substitution therapy in this age group.

Final height outcome in girls with Turner syndrome treated with a combination of low dose oestrogen and oxandrolone

Final stature in girls with Turner syndrome treated with combination of low dose oestrogen and oxandrolone. Nineteen prepubertal girls with Turner syndrome (mean age 10.9 years, range, 8.9-14.2 years) were randomly assigned to receive either oxandrolone (0.05 mg/kg/day) or ethinyloestradiol (40 ng/kg/day) for 1 year. Subsequently the alternate therapy was added and the combination given until attainment of final height. Ethinyloestradiol was gradually increased at the age of 12.5 years in order to induce secondary sexual characteristics. The duration of treatment was a mean of 5.2 years (range, 3.7 years) when the 1st year of monotherapy was included. Therapy produced a sustained acceleration in growth rate for a duration of 4 years and eventually has resulted in an increment of mean adult height of 3 cm relative to pre-treatment projected height with mean values of 146.5 cm versus 143.5 cm respectively. The moderate side-effects observed did not cause any of the girls to discontinue treatment. Nevertheless, amelioration of adult height appears to be modest, notably in comparison to published data of growth hormone treatment and 4 girls had a decrease in final height prediction. CONCLUSION Combination of low dose of oxandrolone and oestrogen may have a moderate but positive impact on final height in girls with Turner syndrome. However, some girls do worse than predicted in term of final height using this regimen. Oestrogen therapy started at low dose around the age of 10 years and increased gradually at approximately 12.5 years to induce secondary sexual characteristics does not have a deleterious effect on adult height in Turner syndrome. In summary, low dose oxandrolone-oestrogen treatment was found to accelerate the tempo of growth in girls with Turner syndrome, but did not appear to have a consistent effect on final height.

Survival and endocrine outcome after testicular relapse in acute lymphoblastic leukaemia

Survival and endocrine status in a cohort of boys with acute lymphoblastic leukaemia (ALL) who started treatment between 1972 and 1987 and subsequently developed a testicular relapse were analysed. During this period there was a significant improvement in the overall event free survival for boys, but no significant decrease in the testicular relapse rate. Thirty three boys had an apparently isolated testicular relapse, whereas 21 boys had a combined relapse. The event free survival for boys with an isolated testicular relapse was 59% at six years (95% confidence interval (CI) 42 to 74%). The event free survival for the 16 patients with a combined relapse who received a second course of treatment was 32% (95% CI 17 to 60%). Those patients receiving adequate second line treatment for an isolated testicular relapse whose first remission was longer than or equal to two years had an event free survival of 82% (95% CI 63 to 93%) at six years. No boy relapsing within two years from diagnosis has survived. Endocrine late effects are significant, with 82% of the boys requiring hormonal treatment at some stage for induction of puberty or continuing pubertal maturation, or both. It is concluded that, despite the increasing intensity of initial treatment for ALL, isolated testicular relapse is treatable by conventional means in most patients. Careful endocrine follow up of these patients is essential as most will require hormone replacement treatment.

Growth hormone treatment without a needle using the Preci-Jet 50 transjector

A new delivery system (Preci-Jet 50) which administers growth hormone through the skin using high pressure and without a needle was evaluated. This device was inconvenient and painful compared with a pen injection system. The conclusion is that the Preci-Jet is not the panacea for solving the problem of compliance with subcutaneous growth hormone injections.

Persistent short stature in children with intrauterine growth retardation: use of growth hormone treatment

Since the early 1970s, it has been demonstrated that growth hormone (GH) treatment improves the short-term growth rate of children with short stature due to intrauterine growth retardation (IUGR). However, it is only in recent years that studies have been conducted in which children with IUGR have been followed to final height. It is appreciated that pharmacological doses of GH are required for the treatment of short children with IUGR, and that the initial effect of rapid advancement of epiphyseal maturation is probably due more to the natural history of growth in children with IUGR than to the GH treatment. Initial studies are promising, showing that the rapid improvement in growth rate is eventually translated into an improvement in final height. However, studies involving a larger number of children with IUGR are necessary in order to quantify this improvement in final height.

A new stress-related syndrome of growth failure and hyperphagia in children, associated with reversibility of growth-hormone insufficiency

BACKGROUND

Growth failure without organic aetiology but associated with behavioural disturbance and psychosocial stress has been termed psychosocial short stature. This condition is not a valid diagnostic entity, but encompasses failure to thrive, stunting secondary to chronic malnutrition, and idiopathic hypopituitarism. Some children show spontaneous catch-up growth when removed from the source of stress, without further treatment, but until now precise definition of this subgroup for the purpose of clinical identification has not been possible.

METHODS

Hospital-referred children with growth failure unrelated to organic pathology, who came from stressful homes, were compared with children of short-normal stature identified from an epidemiological survey (n = 31). Growth-hormone dynamics were studied in the hospital group by a combination of diurnal profiles and provocation tests. The tests were repeated after a hospital stay of 3 weeks away from familial stress. Standard behavioural measures were obtained from home and school.

FINDINGS

In a distinctive subgroup (n = 29), growth-hormone insufficiency was associated with characteristic behavioural features, especially hyperphagia and polydipsia, and a normal body-mass index. When the children were removed from their stressful home circumstances, growth-hormone insufficiency spontaneously resolved only in formerly hyperphagic subjects. 74% of the non-hyperphagic cases (n = 23) were anorexic, with a low body-mass index and normal growth-hormone responses to provocation tests.

INTERPRETATION

We present explicit behavioural and developmental criteria by which the novel syndrome of hyperphagic short stature may be recognised clinically. Such children have a capacity for spontaneous recovery of growth-hormone production on removal from or reduction of stress. Discriminant and predictive validity of the core symptoms are demonstrated. Preliminary familial studies indicate a possible genetic predisposition.

Growth and endocrine sequelae of craniopharyngioma

The growth and endocrine sequelae of 75 children (33 girls and 42 boys) with craniopharyngioma, treated from 1973 to 1994, were studied by retrospective review and by follow up assessment in 66 survivors, with a mean time from initial surgery of 6.7 years (range 1.5 to 19.8 years). Although infrequently complained of, 71% of patients had symptoms to suggest an endocrinopathy at diagnosis. After surgery, multiple endocrinopathies were almost universal, such that 75% of children had panhypopituitarism at follow up. Hypoadrenal crises in association with intercurrent illness contributed significantly to morbidity and mortality, as did the metabolic consequences of concomitant antidiuretic hormone (ADH) insufficiency and absent thirst. Final height in 25 patients was significantly below genetic target height, particularly in the girls, with loss of height potential occurring during the pubertal years. The endocrine morbidity associated with craniopharyngioma and its treatment remains high but manageable with appropriate hormone replacement. However, the combination of ADH insufficiency and an impaired sense of thirst following aggressive surgery and severe hypothalamic injury remains one of the most complex management problems.

Management of childhood craniopharyngioma: can the morbidity of radical surgery be predicted?

Seventy-five children treated for craniopharyngioma between 1973 and 1994 were studied to demonstrate which pre- and intraoperative factors were indicative of a poor outcome as defined by a quantitative assessment of morbidity. This involved a retrospective review of 65 patients and a prospective study of 10 patients focused on clinical details and cranial imaging and a follow-up "study assessment" of 66 survivors performed over the last 2 years. As part of the assessment, 63 patients underwent magnetic resonance imaging with a three-dimensional volume acquisition sequence 1.5 to 19.2 years after initial surgery. Predictors of high morbidity included severe hydrocephalus, intraoperative adverse events, and young age ( < or = 5 years) at presentation. Predictors of increased hypothalamic morbidity included symptoms of hypothalamic disturbance already established at diagnosis, greater height ( > or = 3.5 cm) of the tumor in the midline, and attempts to remove adherent tumor from the region of the hypothalamus at operation. Large tumor size, young age, and severe hydrocephalus were predictors of tumor recurrence, whereas complete tumor resection (as determined by postoperative neuroimaging) and radiotherapy given electively after subtotal excision were less likely to be associated with recurrent disease. Based on these findings, the authors propose an individualized, more flexible treatment approach whereby surgical strategies may be modified to provide long-term tumor control with the lowest morbidity.

Obesity in childhood craniopharyngioma: relation to post-operative hypothalamic damage shown by magnetic resonance imaging

OBJECTIVE

To quantify the extent of hypothalamic damage after surgery for craniopharyngioma using magnetic resonance imaging (MRI) and to relate the findings to changes in body mass index (BMI).

PATIENTS

Sixty-three survivors (36 males, 27 females) of childhood cramopharyngioma were treated surgically between 1973 and early 1994.

METHODS

Cranial MRI was performed at a structured follow-up assessment 1.5-19.2 yr after the initial surgery. Hypothalamic damage was scored as 0 (no visible damage), 1 (intermediate), or 2 (severe).

RESULTS

After surgery there was an increase in BMI standard deviation (SD) from diagnosis to study assessment in all but 7 patients. However, patients with MRI scores of 2 (n = 17) had a significantly greater increase in median BMI SD score at follow-up (+5.5 SD score), compared with +2.5 SD score and +1.1 SD score for patients with MRI scores of 1 or 0, respectively. Of the 17 cases with MRI scores of 2, 10 had a history of extreme weight loss or weight gain at presentation; preoperative neuroimaging demonstrated extensive hypothalamic infiltration by tumor in these cases.

CONCLUSION

MRI gives sufficient anatomical definition to allow assessment of the extent of hypothalamic damage and, thereby, prediction of the patients most at risk for severe post-operative weight gain.

Secondary Amenorrhoea after Total Body Irradiation in Pre-Puberty

Bone marrow transplant (BMT) has been used as part of the overall treatment of refractory malignant diseases. High dose cyclophosphamide and total body irradiation (TBI) are frequently used as conditioning for BMT. Initial regimens included a single fraction of TBI, with doses varying from 7.5-1O Gy, but this was associated with a high incidence of late sequelae including multiple endocrinopathies1. A fractionated irradiation course over 3-4 days of a higher total dose, 12-15 Gy, of TBI is now used1,2. Successfully treated patients with childhood cancer have an increased risk, of developing second tumours. We describe a patient successfully treated for AML who developed multiple endocrine dysfunction and a second benign ovarian tumour.

Imperforate anus, bilateral hydronephrosis, bilateral undescended testes and pituitary hypoplasia: a variant of Hall-Pallister syndrome or a new syndrome

A patient with multiple congenital malformations, including imperforate anus, bilateral cryptorchidism and microphallus, is described. At 4 months of age the infant had generalized convulsions and hypoglycaemia. Bilateral hydronephrosis was diagnosed at 8 months of age. At 10 months he was diagnosed as having panhypopituitarism secondary to anterior pituitary hypoplasia, shown on CT and MRI scans. This clinical picture partially resembles that of Hall-Pallister syndrome. However, the absence of some typical features such as craniofacial and limb abnormalities and, above all, hypothalamic hamartoblastoma, would also suggest the possibility of a new, previously unreported, syndrome.

Investigation of delayed puberty

Delayed puberty is defined arbitrarily on the basis of statistical consideration, when no signs of puberty have occurred at 2.0 SD (13.4 years in girls and 13.8 in boys) above the mean chronological age for the onset of puberty. The vast majority of these patients have no endocrine abnormality and their pubertal development and growth spurt are simply consequences of primary delay (constitutional delay of growth and puberty (CDGP)) or secondary delay due to a chronic disease of childhood, such as asthma. However, a small proportion may have pathological causes of delayed puberty which must be careful identified as specific management may be required. Associated with delayed puberty, the growth spurt is always delayed which is why the condition is described as delayed growth and puberty. Short stature and lack of sexual development may lead to emotional and social difficulties and in some patients their consequences can persist when 'normal' height and full sexual maturation are attained. Recent data also suggest that a delay in the 'tempo' of pubertal maturation may interfere with the normal bone accretion occurring during puberty, later causing osteoporosis. Such findings suggest that a new approach in delayed puberty may be necessary not only for psychological reasons but also for optimizing bone mass accretion.

The effect of a continuous infusion of a somatostatin analogue (octreotide) for two years on growth hormone secretion and height prediction in tall children

OBJECTIVE

Strategies to limit the final height of tall children have centred on the use of high doses of sex steroids to advance skeletal maturation. This limits therapy to the peripubertal years whereas the greatest gain in height is in the prepubertal years. Prepubertal growth is largely GH dependent and previous work has documented modulation of GH secretion by once or twice daily subcutaneous injection of the somatostatin analogue octreotide. In this study we have determined the effects of a nocturnal infusion of octreotide on height prediction, GH and TSH secretion in tall children.

DESIGN

A patient controlled study in which height prediction and 24-hour GH and TSH secretion were compared prior to and during the course of a 2-year treatment programme with a nocturnal infusion of octreotide in a dose of 1-1.5 micrograms/kg body weight given subcutaneously.

PATIENTS

Nine tall children (4M; 5F) aged 7-14 years with final height predictions of 179 cm or greater in the girls and between 183 and 202 cm in the boys were studied.

MEASUREMENTS

Height prediction using the Tanner-Whitehouse system prior to and at the end of 2 years of treatment. Twenty-four-hour serum GH and TSH concentration profiles, thyroxine, IGF-I and GH responses to GHRH(1-29)NH2 were studied prior to and at the end of the first year of therapy.

RESULTS

Treatment with octreotide led to a significant reduction in height prediction in 7 of the 8 children who completed treatment (median reduction 3.5 cm, range +2.8 to -11.5; Wilcoxon, P = 0.05). Twenty-four-hour mean serum GH concentration decreased by 50% (MANOVA, P = 0.03) during therapy and this was accompanied by an increase in the percentage of samples giving values less than 0.5 mU/l (MANOVA, P = 0.02). There was no overall change in the serum GH response to GHRH(1-29)NH2 or serum IGF-I concentrations. Nocturnal serum TSH concentrations were reduced to levels observed during the daytime but these changes had no effect on serum thyroxine values. One patient developed gallstones during the course of therapy.

CONCLUSIONS

A nocturnal infusion of octreotide reduces GH secretion and height prediction in tall children. Therapy with somatostatin analogues allows a reduction in growth rate to be instigated in the prepubertal years reducing the actual height from which will commence the pubertal growth spurt.

Growth arrest despite growth hormone replacement, post-craniopharyngioma surgery

Children with growth failure, whether secondary to an endocrinopathy such as growth hormone deficiency or secondary to neurological handicap with poor nutrient intake, grow at a subnormal rate but it is most unusual for a child to have complete growth arrest.

Predictive factors in the determination of final height in boys with constitutional delay of growth and puberty

Seventy-eight patients who had constitutional delay of growth and puberty were included in a retrospective study to determine whether, at the time of first evaluation, any predictive features could suggest final height outcome. Mean chronologic age was 14.3 years (range, 12 to 18 years), and all were either prepubertal or in an early stage of pubertal maturation (4 ml testicular volume). Initial mean (+/- SD) height standard deviation score was -2.74 (+/- 0.71); 85% had a relatively short spine compared with subischial leg length. Mean (+/- SD) growth rate was 4.8 (+/- 1.6) cm/year, and epiphyseal maturation was delayed by 2.4 (+/- 1) years. Sixteen boys were treated with a sustained-action preparation of testosterone (50 mg monthly for 3 to 4 months), six with oxandrolone (1.25 mg daily for a mean of 4 months), and one with both drugs in sequence. At final height attainment, 58% of the boys failed to achieve their full genetic potential; among the remaining 42%, only 0.7% attained a final height above corrected mid-parental height. The relative disproportion between the segments had no significant change at final height attainment. Regression analysis showed that final height impairment (the difference between mid-parental height and final height) was negatively influenced by standing height and growth velocity when initially evaluated and positively by the degree of segmental body proportion; that is, patients who were taller, were growing at a faster rate, and who had a major degree of segmental body disproportion with a short spine and long leg length attained a final height closer to their mid-parental height, irrespective of the degree of delayed epiphyseal maturation. Neither testosterone nor oxandrolone administered during early puberty modified final height attainment or segmental proportion. We conclude that a late onset in the timing of puberty seems to be deleterious to spinal growth and consequently to final height attainment. An alternative diagnosis should be sought among patients with features of constitutional delay of growth and puberty who do not have a significant degree of body disproportion. In these patients, as well as in those who are extremely short, who have a poor growth rate, or who have an unfavorable genetic potential, an alternative therapeutic approach may be required.

Growth hormone, growth factors and the gonad

During puberty, the growth spurt and stage of pubertal maturation are two processes intimately related both being dependent on the combined action of growth hormone (GH) and sex steroids. While it is well established that both GH and sex steroids are required for a pubertal growth spurt, the precise role played by GH on the timing of onset and rate of progression through different stages of pubertal maturation is not entirely clear. A better understanding of the involved physiologic mechanisms will help clinicians in the management of adolescents with growth and/or pubertal disorders.

The use of a computerized method of bone age assessment in clinical practice

We assessed the reliability and repeatability of a new computerized bone age system, both versions 3.4 and 3.5 (licensed by Discerning System Inc. and Ares Service SA, Serono), able to automatically assess bone age on a left hand and wrist radiograph. This computer system is based upon Tanner and Whitehouse's method (TW2), but there are important differences. Our sample included an initial group of 40 patients who had growth delay/constitutional delay of growth and puberty (n = 10), growth hormone insufficiency/deficiency (n = 15), low birth weight/Silver-Russell syndrome (n = 9), precocious puberty (n = 6), as well as 20 patients with various skeletal dysplasias (multiple epiphyseal dysplasia n = 7, pseudoachondroplasia n = 7, acrodysostosis n = 5, achondroplasia n = 1), 7 girls with Turner syndrome, and 10 boys with nephrotic syndrome on chronic corticosteroid treatment. Multiple anthropometric readings of the same radiographs demonstrated excellent repeatability of the assessment. In addition, the number of times that a manual insertion of a grade was required was similar in four different assessments. The computerized method did not entirely avoid errors in interpretation as the position of the x-ray on the screen was critical. There was a high manual insertion rate in radiographs of children with skeletal dysplasia. However, the computer assessment system, version 3.5, performed adequately for radiographs of children with normal bone morphology and Turner syndrome and had the advantage of a continuous scale of assessment.

Cognitive abilities associated with the Silver-Russell syndrome

There is no consensus opinion on whether or not cognitive impairments are found in the Silver-Russell syndrome. An investigation of a substantial sample was undertaken, using standardised assessments, in 20 boys and five girls aged 6.0 years to 11.8 years. Mean (SD) birth weights were -2.65 (0.95) SD scores, corrected for gestation. At evaluation the children had a mean (SD) age of 8.8 (1.8) years and a mean height of -2.26 (1.5) SD scores. Tests of cognitive abilities included assessments of general intelligence, reading and arithmetic attainments, and a cognitive processing task. Most had some degree of developmental delay: mean (SD) full scale IQ was 86 (24); 32% scored within the learning disability range (that is, IQ < 70); 40% were reading at least 24 months below their chronological age. Current head circumference correlated highly with full scale IQ. Assessments of special educational needs had been completed on 36%; 48% were receiving speech therapy. Approximately half of children with the Silver-Russell syndrome have significant impairment of their cognitive abilities.

Failure to grow: lack of food or lack of love?

One of the most important criteria for good health in childhood is normal growth. Taking regular accurate measurements of length and plotting them on a centile chart is essential to spot early signs of growth disorders. Be alert for a "zig-zag" pattern on the chart: it could indicate psychosocial dwarfism (see opposite). Length is more important than weight for identifying growth disorders. Lack of love, or an adverse emotional or social environment, can cause growth failure even in a child who is eating enough. Such children have a condition called psychosocial dwarfism, which is due to hypopituitarism (too little growth hormone secretion from the pituitary gland). This condition does not respond to growth hormone treatment. Once the child is placed in an alternative environment, eg a good foster home, the hypopituitarism is reversed and rapid "catch-up" growth takes place. It often emerges that such children have been physically, emotionally or sexually abused.

Oral treatment for constitutional delay of growth and puberty in boys: a randomised trial of an anabolic steroid or testosterone undecanoate

Thirty three boys (mean 14.6 years old, range 12.8-16.2 years) with constitutional delay of growth and puberty were randomised into two groups to determine which form of oral treatment would give the better anthropometric response. The two drugs were administered by mouth (one tablet/day) for a mean of 3.5 months (range 3-7 months). At randomisation, 17 boys received testosterone undecanoate (40 mg/day) and 16 oxandrolone (2.5 mg/day). At the start of treatment they were prepubertal or in early puberty, their height SD score was -1.97 in boys treated with testosterone and -2.21 in those treated with oxandrolone, and their growth rates were 4.3 and 4.2 cm/year respectively. Both sex steroid and anabolic steroid treatments induced a significant growth acceleration in all patients except four (three treated with testosterone and one with oxandrolone). When treated with the alternative sex steroid, all four non-responders had a significant anthropometric response. In all boys the induced growth acceleration was sustained when treatment was interrupted. There was no significant difference in the induced growth spurt and bone maturation between the two groups. Spontaneous progress into puberty was achieved in all boys with an increase in testicular volume from a mean of 4.6 to 8.5 ml. The rate of development in secondary sexual characteristics was also similar in the two groups. These data suggest that oral testosterone and oxandrolone are equally effective in the treatment of growth delay in boys with constitutional delay of growth and puberty.

Alterations in growth hormone secretion and clearance in peripubertal boys with chronic renal failure and after renal transplantation. Cooperative Study Group of Pubertal development in Chronic Renal Failure

To elucidate the endocrine mechanisms underlying the pubertal growth failure observed in patients with chronic renal failure (CRF), we used deconvolution analysis to estimate the rates of GH secretion and elimination in nighttime plasma GH profiles of peripubertal boys with CRF and after renal transplantation (Tx). Forty-three boys with advanced CRF (conservative treatment with glomerular filtration rate < 25 mL/min.1.73 m2 or dialysis; CT/D group), 38 boys after Tx, and 40 healthy control boys were studied. The estimated plasma GH half-life (mean +/- SEM) was significantly higher (P < 0.05) in CRF (25 +/- 1.8 min) than in Tx patients (21 +/- 1.6 min) and controls (20 +/- 0.5 min). In the pre- and early pubertal CT/D boys, the calculated GH secretion rate was low normal or reduced when expressed in absolute numbers or normalized per unit distribution volume or body surface. In late puberty, whereas body surface-corrected GH secretion was double the prepubertal value in normal boys (389 +/- 56 vs. 868 +/- 113 micrograms/m2.11 h; P < 0.01), it did not differ significantly from the prepubertal rate in CT/D boys (281 +/- 59 vs. 389 +/- 56 micrograms/m2.11 h). GH hyposecretion resulted from a decrease in the mass of GH released within each burst, whereas burst frequency was unchanged. In the Tx group, GH secretion rates were significantly reduced in the prepubertal (221 +/- 39 micrograms/m2.11 h; P < 0.05) and late pubertal period (266 +/- 64 micrograms/m2.11 h; P < 0.01). The mass of hormone secreted per burst was significantly reduced at each pubertal stage, whereas GH secretory burst frequency tended to be increased (significant in prepubertal group, P < 0.05). The GH secretion rate was positively correlated with plasma testosterone levels (r = 0.58; P < 0.0001) in controls, but not in CT/D or Tx patients. GH secretion rates were lower than expected at each level of plasma testosterone in both patient groups except CT/D boys with plasma testosterone below 0.9 nmol/L. In the Tx group, GH secretion rate was positively correlated with relative height (r = 0.31; P < 0.05). The dosage of corticosteroids administered for immunosuppression was negatively correlated with GH burst mass (r = -0.42; P < 0.01) and GH secretion rate (r = -0.29; P = 0.08) and positively correlated with GH burst frequency (r = 0.49; P < 0.01). We conclude that in peripubertal boys with CRF, a state of GH hyposecretion is associated with an increase in the apparent plasma half-life of GH.(ABSTRACT TRUNCATED AT 400 WORDS)