17alpha-hydroxylase/17,20-lyase deficiency as a model to study enzymatic activity regulation: role of phosphorylation.

Cytochrome P450 17alpha-hydroxylase (CYP17) is a single gene-encoded protein with two activities: 17alpha-hydroxylase and 17,20-lyase. The two catalytic activities are differentially regulated in health and disease. We took advantage of naturally occurring human mutations to understand the molecular bases of this differential regulation. We identified eight novel mutations in the CYP17 gene, different in nature and spread throughout the gene. As posttranslational modifications appear to be important for activity control, we investigated the phosphorylation state of wild-type and mutant CYP17 proteins. Although phospholabeled protein was seen when the wild-type and most mutant proteins were expressed, no phosphorylation was detected for the F417C mutant. F417C is the only 17,20-lyase deficiency case confirmed at the molecular level and represents the first phosphorylation CYP17-deficient mutant. In search of the physiological agents involved in this process, the effect of cAMP was tested on activity and phosphorylation state of our mutant CYP17 proteins. cAMP stimulates activity and phosphorylation in all cases, except in the F417C and R35L mutants. The lack of response to the physiological second messenger might explain the different phenotypes. The F417C mutant protein, which is already shown to be associated with the lack of electron transfer, provides for the first time a link between the electron transfer system and the phosphorylation state of the CYP17 enzyme in the control of 17,20-lyase activity.

Acute metabolic effects of human growth hormone on 15N-nitrogen balance in patients with thalassaemia as compared to patients with other types of short stature.

The acute response to various doses of human growth hormone (hGH) was determined in short patients with thalassaemia and compared to that in patients with classic growth hormone deficiency and Turner's syndrome. Nitrogen balance was analyzed using the stable isotope 15N. While patients with growth hormone deficiency responded with a marked nitrogen retention (+2.9 +/- 0.4 to +6.1 +/- 0.6 mg 15N/kg) to small doses of hGH (2 x 3 IU/m2), those with Turner's syndrome had a higher basal balance, but responded much less (+3.1 +/- 0.7 to +3.7 +/- 1.8 mg 15N/kg). They required a double dose of hGH (2 x 6 IU/m2) to achieve a significant retention (+4.1 +/- 1.0 to +7.1 +/- 0.4 mg 15N/kg). The thalassaemic patients responded still less than the patients with Turner's syndrome to 2 x 6 IU/m2 (+7.7 +/- 0.3 to +8.0 +/- 0.4 mg 15N/kg), and even hGH doses up to 2 x 12 IU/m2 had little effect, indicating a relative resistance to hGH. In conclusion, no or little effect is to be expected from long-term hGH treatment at low doses in thalassaemic patients. When it is decided to treat these patients, the dose should be about 4 times higher than a regular replacement dose in growth hormone deficiency.

15 beta-hydroxylated steroids may be diagnostically misleading in confirming congenital adrenal hyperplasia suspected by a newborn screening programme.

UNLABELLED: In a Swiss screening programme for detection of congenital adrenal hyperplasia (CAH), 27 of over 120,000 newborns examined from 1992 to 1994 were further studied because of persistingly high 17 alpha hydroxyprogesterone (17OHP). Out of 27, 11 were later confirmed to have CAH by specific gas chromatography of urinary steroids and ACTH test at age 3-4 months. Of 27, 11 were born at term (7 confirmed 21-hydroxylase deficiency, one 11 beta-hydroxylase deficiency). Out of 27, 16 were preterm newborns. Of them, only 2 were confirmed to have CAH (one 21-, one 11 beta-hydroxylase deficiency). In 3 cases with high 17OHP, but later not confirmed CAH, what appeared to be a pregnanetriolone peak in the gas chromatograms was shown to be 3 beta, 15 beta, 17 alpha-pregnenetriol. This compound may be misleading in confirming the diagnosis of CAH. 15 beta-Hydroxylated compounds occur in fetuses, neonates, and amniotic fluid. Since human tissues do not have 15 beta-hydroxylating capacity, their origin is unclear. However, since some bacteria (Bacillus megatherium) and mycelial fungi (fusaria) are known to hydroxylate steroids in position 15 beta, it is likely that this compound is formed by micro-organisms in the enterohepatic circulation of newborns or their mothers. CONCLUSION: For the confirmation of the diagnosis of CAH in cases suspected by screening, later ACTH stimulation and specific steroid analysis are necessary.

Conversion from pure 17,20-desmolase- to combined 17,20-desmolase/17 alpha-hydroxylase deficiency with age.

A previously described phenotypically female 46,XY-individual with 17,20-desmolase deficiency was followed from adolescence to adulthood. While at age 16.9 years her 17 alpha-hydroxylating capacity was normal and steroids not hydroxylated in position 17 low, decreasing 17 alpha-hydroxylated and increasing unhydroxylated steroids were observed thereafter up to the age of 25.2 years. Simultaneously with the steroid changes, previously normal blood pressure (110/80 mmHg) increased (180/130 mmHg). Since 17 alpha-hydroxylation and 17,20-desmolase activity are regulated by one cytochrome P450-17 alpha, it is concluded that, in this same patient, 17 alpha-hydroxylase activity was normal during childhood and adolescence, but decreased in the young adult. 17,20-desmolase activity, by contrast, was completely absent already in the fetus, causing absence of masculinization. The factors modulating this difference in cytochrome P450-17 alpha activity with age are as yet unknown.

Effect of recombinant human growth hormone on urinary 15N-nitrogen balance in girls with Turner syndrome as compared to children with growth hormone deficiency.

15N-nitrogen balances before and on human growth hormone (hGH) were studied in 13 girls with Turner syndrome (TS) aged 4.4-16 (median 13.2) years (45,X0 or equivalent, no X0/XX mosaicism, no estrogen replacement). The results were compared with those reported from 9 patients with growth hormone deficiency (GHD). The TS patients received subcutaneous hGH doses of 2 x 3 (group A, n = 6), 3 x 2 (group B, n = 3), or 2 x 6 (group C, n = 4) IU/m2 on consecutive days. The mean 15N dose given to the patients of groups A and C was higher (13.6 mg/kg) than that given to those of group B (2.7 mg/kg). The lower hGH doses in the first two groups induced small positive mean 15N balance changes (+0.6 +/- 0.6 mg/kg 15N, group A; +0.03 mg/kg, group B). The higher hGH dose in group C caused a more marked mean balance change (+3.0 mg/kg 15N) comparable to that in GHD patients (+3.2 mg/kg). Individual variation of response, however, was larger in patients with TS than in those with GHD. With low and high hGH doses, there were responders and nonresponders. It is concluded from this pilot study in a small number of cases that 15N balance studies might be potentially useful to choose the appropriate hGH dose for long-term treatment in TS patients.

Effect of a recombinant human growth hormone preparation on the urinary 15nitrogen balance in growth-hormone-deficient children.

In 10 patients with idiopathic growth hormone (GH) deficiency (9 boys and 1 girl, aged 7.5-14.5 years, mean 12.1 +/- 2.2 years), urinary 15N-balance studies were performed before and on recombinant hGH (2 x 3 IU/m2 of body surface area subcutaneously on consecutive days). Before and on the 2nd day of recombinant hGH, 99% 15N-labeled ammonium chloride (0.05 g/kg, divided in 3 doses per day, corresponding to 389 +/- 30 mg/m2 of 15N) was administered and 24 h urine was collected. In urine, total nitrogen and the percentage of 15N were measured. From the ingested and excreted quantity, a urinary 15N balance was calculated. Mean 15N percentage from total N was 3.3 +/- 0.5. In 9 patients, basal 15N balance was +79 +/- 15 mg/m2 or +2.9 +/- 0.4 mg/kg. On recombinant hGH, it was +166 +/- 16 mg/m2 or +6.1 +/- 0.6 mg/kg (p less than 0.001). The recombinant hGH-induced positive 15N balance change was +87 +/- 17 mg/m2 or +3.2 +/- 0.6 mg/kg. 1 patient with a higher basal 15N balance (+196 mg/m2, +7.1 mg/kg) had no positive 15N balance change due to latent hypothalamic hypothyroidism. In previous similar studies with pituitary hGH the change of 15N balance was +80 +/- 27 mg/m2 or +2.8 +/- 1.1 mg/kg. It is concluded that the acute nitrogen-retaining effect of recombinant hGH is at least equal to that of pituitary hGH.

Identification of new steroids in patients with 17 alpha-hydroxylase deficiency by capillary gas chromatography/mass spectrometry.

Urines of two children with 17 alpha-hydroxylase deficiency contained a number of 5-pregnane- and pregnenediols, -triols and -tetrols with a hydroxy or oxo group in position 11 of the steroid ring. They are formed mainly from progesterone via 11-hydroxyprogesterone, pregnanolone and corticosterone, respectively, or from pregnenolone. Three metabolites not previously described, 16-hydroxypregnenolone, 6,21-dihydroxypregnanediol and 6-hydroxytetrahydrocorticosterone, were identified.

Ovarian steroidogenesis in an adrenalectomized girl with 21-hydroxylase deficiency.

A girl with congenital adrenal hyperplasia due to 21-hydroxylase deficiency could not be controlled by conventional treatment, and was adrenalectomized at age 8.5 years (bone age 13.5 years). After surgery, puberty and menarche occurred. On replacement therapy, her progress was uneventful up to the age of 16 years, when menstruations ceased and signs of virilization reappeared. Testosterone, androstenedione, and 17-hydroxyprogesterone in plasma, and pregnanetriol in urine were high, but DHEA in plasma, and pregnenetriol and pregnanetriolone in urine were low. Oestrogens in plasma were normal. There was no steroid response to ACTH, and marked, but somewhat slow suppression by dexamethasone. HMG induced a strong rise in oestrone and oestradiol. Ethinyloestradiol reduced not only oestradiol in plasma, but also testosterone, androstenedione, and 17-hydroxyprogesterone. With subsequent dexamethasone treatment, menstruation restarted, and the values returned to normal. It is concluded that virilization may reoccur in patients with 21-hydroxylase deficiency even after adrenalectomy, and that the ovaries in this patient contain some tissue, which has properties of adrenal (suppressibility by dexamethasone) and ovarian tissue (suppressibility by ethinyl oestradiol, preference for delta 4-pathway, low steroid 11-oxygenation) at the same time.

Transient impairment or delay of urinary trihydroxypregnanone (THS) response to metyrapone in boys with delayed adolescence and in patients with isolated growth hormone deficiency.

Twenty three boys with delayed adolescence (age 15.7 +/- 2.0, bone age 12.4 +/- 2.1 years) were studied. Their cortisol response to insulin was normal. After oral metyrapone (500 mg/m2 by mouth) one to three consecutive 12 h urine samples were collected for analysis of THS. Thirty seven tests with 37 first, 21 second, and 11 third samples were carried out. The results could be divided into two main groups: 25 tests (group A) were subnormal in the first sample, 12 of them with a very weak (40 +/- 8 micrograms/m2/12 h) and 13 with an insufficient (191 +/- 16 micrograms/m2/12 h) THS response. Values in the second and third sample were higher, indicating a delayed response. In 12 tests (group B), the results were normal (1016 +/- 143 micrograms/M2/12 h) in the first and lower in the second and third samples. In three patients with repeated tests, there was improvement with increasing bone age. The THS-responses to metyrapone did not correlate with those of growth hormone, gonadotrophins, and TSH to stimuli. It is concluded that the THS-response to a single dose of metyrapone may be temporarily insufficient or delayed in delayed adolescence. We interpret this finding as showing transiently reduced or slow hypothalamic responsiveness.

Hydantoin-5-propionic aciduria in folic acid nondependent formiminoglutamic aciduria observed in two siblings.

Hydantion-5-propionic acid was detected in massive amounts in the urine of two previously described sisters with folic acid nondependent formiminoglutamic aciduria. HPA was identified rigorously, e.g. by gas chromatography-mass spectrometry, and was measured quantitatively by selected ion monitoring (mass fragmentography) using deuterated HPA as internal standard. Before histidine loading, both girls with the postulated formiminotransferase deficiency excreted an amount of HPA more than 50 times greater than the control subjects. After histidine ingestion, HPA excretion was still doubled or tripled. With the exception of the father, the values for the other members of the family also markedly exceeded the normal range and were of the same order of magnitude as in folate deficiency. Measurement of HPA excretion in urine seems to be a valuable supplement or alternative to the enzymatic FIGu test for the detection of general or functional folate deficiency or impaired folate utilization and it will be indispensable for the detection of (as yet unknown) 4-imidazolone-5-propionic acid hydrolase deficiency.