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Biomedical subjects

A G Smals

Publications and source records attributed to A G Smals.

At least 145 records · Page 8Linked to original sources
PubMed1982

Adrenocorticotropin and cortisol responsiveness to thyrotropin-releasing hormone and luteinizing hormone-releasing hormone discloses two subsets of patients with Cushing's disease.

In 23 consecutive patients with Cushing's disease and 52 control subjects, the responses of ACTH and cortisol to TRH and LRH were investigated. From the pattern of cortisol levels after the administration of the releasing hormone in the controls, a criterion for paradoxical responsiveness could be derived (maximum cortisol increase, greater than 6.0 micrograms/100 ml). According to this criterion, 9 patients with Cushing's disease showed a paradoxical responsiveness to one or both releasing hormones (3 to both TRH and LRH, 3 to TRH alone, and 3 to LRH alone; group I). In all patients tested, paradoxical responses of cortisol were preceded by paradoxical increments in ACTH. The remaining 15 patients showed no paradoxical increments in ACTH or cortisol after TRH or LRH (group II). ACTH levels in group I (89 +/- 28 pg/ml) were significantly lower than those in group II (185 +/- 164 pg/ml; P less than 0.02). Nevertheless, in both groups, a similar plasma cortisol level was found, suggesting a relatively higher bioactivity of ACTH in group I. A second difference between both groups was a lower amplitude of cortisol variability during the day in group I. The 2 groups did not differ in clinical data, such as age, sex distribution, sellar volume, and duration of disease, or dexamethasone suppressibility, bromocriptine sensitivity, and basal PRL levels. These latter findings do not favor an intermediate lobe origin of Cushing's disease in patients with paradoxical responses to TRH/LRH. To conclude, TRH/LRH responsiveness of ACTH/cortisol discloses two subsets of patients with Cushing's disease.

Adolescent↗
PubMed1982

Enhancement of gonadotrophin induced 17,20-lyase suppression one week after human chorionic gonadotrophin priming.

A single injection of 1500 IU of human chorionic gonadotrophin (hCG) in normal men, induced a block in the conversion of 17-hydroxyprogesterone (17-OHP) to testosterone (T) which reached its maximum 24 h after hCG loading. One week after hCG administration both basal 17-OHP (3.8 +/- 0.6 vs 5.1 +/- 0.5 nmol/l, P less than 0.02) and T levels (15.1 +/- 1.7 vs 18.5 +/- 2.3 nmol/l, P less than 0.05) were about 20% lower than before hCG exposure. The ratio 17-OHP to T (0.29 +/- 0.04 vs 0.31 +/- 0.04, P greater than 0.10) was however similar, suggesting recovery from the prior 17,20-lyase suppression at a lower overall capacity of T synthesis. hCG administration one week after the priming dose elicited an increase in the ratio 17-OHP to T, which was about twice as high as after the first hCG injection. Together the data suggest: 1) suppression of testicular steroidogenesis proximal to 17-OHP one week after hCG priming, 2) enhanced hCG induced 17,20-lyase suppression one week after hCG exposure.

Adult↗
PubMed1982

Aldosterone, sodium and potassium in essential hypertension.

Eighty-five patients with essential hypertension received a restricted sodium diet for 10 days. During the last 5 days sodium intake was increased by oral administration of an additional 300 mmol of NaCl. At the end of both periods blood pressure, plasma and urinary concentration of Na and K, and 24-hour secretion rate of aldosterone (ASR) were determined. ASR in the hypertensives was after NaCl loading slightly higher than that in 21 normotensive controls. Aldosterone secretion rates were highest in patients with the lowest plasma K levels after loading with NaCl. This relationship between ASR and potassium was not found after NaCl restriction. After both NaCl restriction and NaCl loading the plasma K concentrations were lowest in patients with the highest mean arterial pressures. From statistical analysis of the relations between plasma Na, plasma K, ASR and mean arterial pressure it seems highly unlikely that aldosterone plays a prime role in the relation between the height of the blood pressure and the concentration of plasma K in essential hypertension. Our data seem in line with the presence of a primary abnormality in electrolyte metabolism in essential hypertension and slight aldosteronism after salt loading as its sequela.

Aldosterone↗
PubMed1981

Dichotomy between serum free triiodothyronine and free thyroxine concentrations in familial thyroxine-binding globulin deficiency.

The mean serum total T4 (3.2 +/- 1.0 micrograms/100 ml) and T3 levels (83 +/- 29 ng/100 ml) in eight euthyroid patients with T4-binding globulin (TBG) deficiency from two families were significantly lower than those in either the unaffected relatives (P less than 0.05) or the control subjects (P less than 0.01). The lowest T4 and T3 values were found in the four hemizygotes (2.4 +/- 0.2 micrograms/100 ml and 69 +/- 25 ng/100 ml, respectively). In contrast to the absolute T4 and T3 levels, the mean percentages of free T4 and free T3 in the affected members were about twice as high as those in either the unaffected relatives or the controls. Despite an elevated percentage of free T4 in each of the TBG-deficient members, the mean absolute free T4 (FT4) level (0.89 +/- 0.20 ng/100 ml) was significantly lower than those in both control groups [1.31 +/- 0.2 ng/100 ml (P less than 0.02) and 1.24 +/- 0.30 ng/100 ml (P less than 0.01), respectively]. Serum FT4 levels were subnormal in three of four hemizygotes. In contrast to FT4, the mean FT3 level in the affected members (0.33 +/- 0.04 ng/100 ml) was significantly higher than that in either the nondeficient relatives (0.25 +/- 0.02 ng/100 ml; P less than 0.02) or the control subjects (0.26 +/- 0.04 ng/100 ml; P less than 0.02), whereas the ratio of FT3 to FT4 was about twice as high. The data suggest that in TBG deficiency, euthyroidism in maintained by a subtle equilibrium between low FT4 and high FT3 levels.

Adolescent↗
PubMed1981

The effect of low dose oestrogens on short-term growth and concomitant biochemical phenomena in girls with tall stature.

Using a simple non-invasive ulnar length measuring technique a 70 to 80% decrease in ulnar growth velocity was found during one interval of 9 weeks of low dose ethinyloestradiol administration (0.050 mg daily) in girls with tall stature. This decrease in ulnar growth velocity was found to be statistically significant within 6 and even 3 weeks after starting oestrogen loading whereas the change in body growth velocity was only significant after 9 weeks. After interpreting oestrogen administration, ulnar growth velocities increased again but to values tending to be lower than before ethinyloestradiol loading. Serum alkaline phosphatase activities and plasma inorganic phosphorus and calcium levels also decreased significantly during oestrogen therapy within 9 weeks. The results found illustrate that the measuring technique used enables evaluation of the short-term effect of hormonal treatment on growth and thereby related biochemical phenomena.

Adolescent↗
PubMed1980

Dissociated responses of plasma testosterone and 17-hydroxyprogesterone to single or repeated human chorionic gonadotropin administration in normal men.

After both single (1500 IU) and daily repeated (1500 IU daily for 3 days) im administration of hCG, peak values of 17-hydroxyprogesterone (17OHP) were achieved 24 h after the single or first injection, whereas plasma testosterone (T) levels reached their maximum 48 h later. After the peak value of 17-OHP at 24 h, both steroids ran dissociated courses with the T levels rising and the 17-OHP levels falling. In both the single and repeated hCG experiments, the initial rise of 17-OHP was more pronounced than that of T, leading to a steep temporary increase of the 17-OHP to T ratio in the first 24 h. Repeated hCG administration for 3 days to the same subjects elicited T responses at 48 and 72 h quantitatively similar to those produced by single hCG loading, although the 17-OHP response appeared slightly higher in the multiple dose experiment. The data indicate that exogenous gonadotropins may influence testicular steroidogenesis not only quantitatively, but also qualitatively, possibly by altering enzyme activities.

Adult↗
PubMed1980

Lack of a biphasic steroid response to single human chorionic gonadotropin administration in patients with isolated gonadotropin deficiency.

Single im administration of 1500 IU hCG evoked a biphasic response of 17-hydroxyprogesterone (17-OHP) and testosterone (T) in six eugonadotropic men, with an early peak after 4 h, a nadir at 5 h, and a second peak 24 and 72 h after hCG loading, respectively. Remarkably, in six patients with isolated gonadotropin deficiency, the early rise of both 17-OHP and T was absent, whereas the late peak was attenuated and somewhat delayed. This lack of an immediate response in these hypogonadotropic patients might be accounted for by the lack of gonadotropin-induced enzyme systems capable of rapid steroid synthesis. In the normal men, the 17-OHP rise was more pronounced than the T increase, and thus, from 4 h on, a gradually rising 17-OHP to T ratio was observed, which reached its maximum 24 h after the hCG injection. In contrast, in the hypogonadotropic patients, the 17-OHP to T ratio did not rise but rather decreased to minimal values 72 h after hCG loading. These data suggest that in normal men, but not in hypogonadotropic patients, hCG may rapidly modify steroidogenesis by temporarily depressing the conversion of 17-OHP to T.

Adult↗
PubMed1980

Tamoxifen suppresses gonadotropin-induced 17 alpha-hydroxyprogesterone accumulation in normal men.

Intramuscular administration of 1500 IU hCG daily for 3 days induced a transient accumulation of 17 alpha-hydroxyprogesterone (17 OHP) relative to testosterone (T) in normal men, reaching its maximum 24 h after the first injection (17 OHP to T ratio, 1.7 +/- 0.3 times baseline; P < 0.01). Simultaneous administration of hCG and the estrogen antagonist tamoxifen (20 mg twice daily) almost completely abolished the hCG-induced steroidogenic block localized between 17 OHP and T (17 OHP to T ratio at 24 h, 1.1 +/- 0.1 times baseline; P < 0.01 vs. hCG alone). These data indirectly suggest that, in man, the hCG-induced steroidogenic lesion might be mediated through its estrogen-stimulating effect.

Adult↗
PubMed1980

Nocturnal, daytime, and postural changes of plasma aldosterone before and during dexamethasone in adenomatous and idiopathic aldosteronism.

The relative importance of ACTH and the renin angiotensin system for control of aldosterone was studied in eight patients with adenomatous primary (APA) and four with idiopathic aldosteronism (IHA). Plasma aldosterone (PA) and cortisol (PC) were measured in blood collected during the night at 15-min intervals between 0500--0800 h by integrated sampling on day 1 and in casual samples during the daytime while patients were in the upright and in the supine position (days 1 and 2, at 1200, 1600, and 2000 h). PRA was measured in all daytime samples. On days 3, 4, and 5, 2 mg dexamethasone were given, and the same protocol for blood sampling was repeated on days 4 and 5. During the night, mean PA in IHA patients was markedly lower than that in APA patients. PA patients correlated with PC in both groups. Dexamethasone reduced the mean nocturnal PA in both groups to equal proportions. In the daytime, the mean recumbent PA in IHA patients was also significantly lower than that in APA patients but was equal in both groups while subjects were in the upright posture. Daytime PA significantly correlated with PC in APA patients and with PRA in IHA patients. During upright posture, dexamethasone did not reduce daytime PA in either group. In the supine position, dexamethasone reduced daytime PA values in APA but not in IHA patients. Thus, short time fluctuations of PA during the night are equally influenced by ACTH in APA and IHA patients, though at markedly different levels of aldosterone production. During the daytime, the influence of ACTH on PA remains apparent in the group with APA. However, the renin-angiotensin system seems to play a predominant role in the control of PA during the daytime in patients with IHA. During dexamethasone and ACTH suppression, PA in APA patients rises in response to upright posture as it does in IHA patients.

Adenoma↗