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Biomedical subjects

P Chanson

Publications and source records attributed to P Chanson.

At least 127 records · Page 7Linked to original sources
PubMed1988

Absence of receptors for thyrotropin (TSH)-releasing hormone in human TSH-secreting pituitary adenomas associated with hyperthyroidism.

In patients with TSH-secreting pituitary adenomas associated with hyperthyroidism, TSH secretion usually does not respond to exogenous TRH stimulation. To determine the basis for this unresponsiveness, we studied TRH binding to the membranes of two such TSH-secreting pituitary adenomas. The patients, a 28-yr-old man and a 60-yr-old woman, had clinical and biochemical hyperthyroidism with increased serum TSH levels (15.7 and 14 mU/L, respectively; normal range, 1.1-7.2) and alpha-subunit to TSH molar ratios greater than 1 (2.4 and 1.7, respectively). Neither patients had an increase in serum TSH in response to TRH (200 micrograms, iv). Immunocytochemistry of the two adenomas, removed by transsphenoidal surgery showed a pure population of thyrotropic cells. Binding studies were performed by incubation of tumor cell membrane suspensions with increasing amounts of [3H]TRH. Two PRL-secreting adenomas and one normal human pituitary were used as controls. The characteristics of the TRH-binding sites from the control tissues were similar to those previously reported (Kd, 56, 30, and 49 nM; maximum binding, 187, 46, and 94 fmol/mg protein, respectively). In contrast, no specific TRH binding was found in the two TSH-secreting adenomas. We conclude that the unresponsiveness of TSH after TRH administration is related to the absence of specific TRH-binding sites in these thyrotropic tumors.

Adenoma↗
PubMed1988

Management of early postoperative diabetes insipidus with parenteral desmopressin.

Management of early postneurosurgical diabetes insipidus (DI) requires parenteral vasopressin before intranasal administration of desmopressin-1 desamino-8 D arginine vasopressin (dDAVP) can be initiated. We have evaluated in 15 neurosurgical patients the effect and the tolerance of a 3-day regimen of dDAVP administered im every 12 h. Patients were randomly ascribed to one of 3 treatment groups: 1 microgram (N = 6), 2 micrograms (N = 5) or 4 micrograms (N = 4) were administered twice daily. dDAVP was effective whatever the dose, and DI was corrected by the 6th h of treatment. Effects were maximal on diuresis and urinary osmolality from the 18th h onwards. The effects were sustained throughout the treatment period. Reversal to pretreatment status occurred 24 h after the last injection. Moreover, 72 h after the last injection, natremia and osmolality reached values significantly below pretherapeutic values. The tolerance was excellent: hyponatremia which occurred in 11 patients, either occasionally or throughout the treatment period, remained mild and never had clinical consequences. In conclusion, before initiation of intranasal dDAVP, a 3-day treatment by 1, 2 or 4 micrograms of dDAVP injected im twice daily in neurosurgical patients corrected DI. Mild overhydration owing to a positive fluid balance was a side-effect which is also encountered in other therapeutic methods necessitating meticulous control of water intake.

Adolescent↗
PubMed1987

[Thyrotropic pituitary adenoma. Clinical aspects, course and treatment].

Thyrotropic pituitary adenoma is a rare disease fortunately diagnosed with increasing frequency. Its originality lies in the fact that it occurs in two very different pathological contexts. The first form raises few problems: the occurrence of a pituitary tumoral syndrome in a patient with hypothyroidism, even of relatively short duration, should suggest the diagnosis. In such cases of reactive thyrotropic adenoma, simple correction of the hypothyroidism by replacement therapy seems to be capable not only of curing the thyroid disorder and lowering TSH values, but also of promoting regression of the pituitary tumour. Primary autonomous adenoma responsible for TSH hypersecretion followed by thyrotoxicosis belongs to the realm of inappropriate TSH secretion, and it should be diagnosed whenever high, or even normal (at least non-suppressed). TSH levels coexist with peripheral hyperthyroidism. As a rule, the presence of a pituitary tumour differentiates this adenoma from non-tumoral inappropriate TSH secretion due to resistance to thyroid hormones. Primary thyrotropic pituitary adenoma is treated by surgery. In case of failure or relapse, radiotherapy or medical treatment with a dopaminergic agonist or a long-acting somatostatin analogue may be considered.

Adenoma↗
PubMed1987

Evidence of an endogenous digitalis-like factor in the plasma of patients with acromegaly.

Evidence suggests that plasma-volume expansion leads to the release of a digitalis-like factor, which is thought to act on the renal tubular cells and cause natriuresis. We postulated that this factor might be present in patients with acromegaly (in whom plasma volume is elevated) and might return to normal levels when the disease was treated successfully. We measured the ability of plasma extracts from patients with acromegaly to inhibit the binding of ouabain to the sodium pump in normal red cells and to inhibit the enzymatic activity (sodium-potassium-ATPase) of the sodium pump in membrane preparations from normal kidneys. In 21 patients with active acromegaly, the mean (+/- SE) level of ouabain-binding inhibition (1.56 +/- 0.38) was higher (P less than 0.01) than that in either 11 successfully treated patients (0.18 +/- 0.05) or in 27 normal controls (0.19 +/- 0.03). The inhibition of sodium-potassium-ATPase activity by plasma was also greater in patients with active acromegaly (38.1 +/- 6.8 percent) than in successfully treated patients (18.4 +/- 5.6 percent, P less than 0.05) or controls (21.1 +/- 2.7 percent, P less than 0.05). Significant correlations were found between plasma volume and ouabain-binding inhibition in 23 patients (r = 0.72, P less than 0.01) and sodium-potassium-ATPase inhibition in 19 patients (r = 0.62, P less than 0.01). Pituitary adenomectomy decreased plasma volume and the inhibition by plasma of ouabain binding. We conclude that an endogenous digitalis-like factor is present in the plasma of patients with chronic volume expansion due to acromegaly. These results are consistent with the hypothesis that this natriuretic factor may have a physiologic role in water and sodium homeostasis.

Acromegaly↗
PubMed1987

Ultralow doses of vasopressin in the management of diabetes insipidus.

Management of postoperative diabetes insipidus (DI) frequently requires intermittent treatment with multiple subcutaneous injections of pituitrin or vasopressin, in doses averaging 20 IU/24 h. Use of a syringe pump for a continuous infusion of ultralow doses of pituitrin produced uniform, constant, and sustained reduction of urinary output, thus facilitating regular fluid replacement. Twelve patients with postoperative DI received iv pituitrin at a dose of 1.6 +/- 0.26 mIU/kg X h (1 to 2 IU/24 h). The antidiuretic effect began at the third hour of treatment, peaked by the sixth hour (diuresis of 37 ml/h, specific gravity of 1.018 +/- 0.002), and was sustained throughout infusion. Polyuria recurred 3 h after the infusion was discontinued; this rapid reversibility is highly advantageous when excessive fluid intake causes overhydration. Pressor effects were not observed during the treatment period.

Adolescent↗
PubMed1987

Alteration of gentamicin and cefazolin kinetics with control of the hypothyroid state in humans.

We studied the effect of the control of the hypothyroid state in humans on the pharmacokinetic parameters of cefazolin and gentamicin after a single intravenous injection. These two antibiotics were chosen because of their different patterns of binding to serum albumin (0% for gentamicin and 82% for cefazolin). In hypothyroidism, the behavior of cefazolin only was altered, with a decrease in the total body clearance, possibly due to reduced urinary excretion, and a decrease in the volume of distribution without a significant alteration of cefazolin binding to serum protein.

Cefazolin↗
PubMed1987

The effect of subcutaneous infusion versus subcutaneous injections of a somatostatin analogue (SMS 201-995) on the diurnal GH profile in acromegaly.

Multiple sc injections of a long-acting somatostatin analogue (SMS 201-995) are currently used in the treatment of acromegaly. However, plasma GH concentration often reaches a pathological level (less than 5 micrograms/l) between two injections. In seven patients with active acromegaly we compared, in a short-term trial, the effect of SMS 201-995 administered by continuous sc infusion (50 micrograms and 100 micrograms a day) and by three sc injections (100 micrograms each). In six patients, plasma GH levels were significantly reduced regardless of the mode and dose of treatment (P less than 0.05). However, comparing diurnal profiles, 100 micrograms continuous sc infusion was more effective than discontinuous administration in reducing the number of GH levels above 5 micrograms/l (P less than 0.01). In two patients, continuous infusion was the only way to decrease all plasma GH values below 5 micrograms/l during the diurnal profile determination. Moreover, even when, in a long-term study, the dose of multiple injections was progressively increased to 500 micrograms three times a day, GH levels remained consistently elevated in one of these patients. Thus, in some acromegalic patients continuous sc injection seems currently the most efficient way of treatment with SMS 201-995.

Acromegaly↗
PubMed1987

[Discordance between the short and standard metyrapone tests in isolated corticotropin insufficiency].

A 71-year-old man presented with clinical and common biological features of secondary adrenal insufficiency. Basal ACTH level was in the normal range. As it has been previously reported in ACTH deficiency, cortisol response to ACTH-test was normal. A single-dose metyrapone test, performed to confirm the diagnosis of adrenal insufficiency, gave unexpectedly normal results. However 11-desoxycortisol (compound S) response to standard-metyrapone test was subnormal ascertaining the diagnosis of ACTH-deficiency. Thus normal responses to single-dose metyrapone test do not imperatively exclude secondary adrenal failure.

Adrenal Insufficiency↗
PubMed1984

Paradoxical response of thyrotropin to L-dopa and presence of dopaminergic receptors in a thyrotropin-secreting pituitary adenoma.

We studied the dopaminergic control of TSH secretion in a patient with hyperthyroidism due to a TSH-secreting pituitary adenoma. A 34-yr-old previously thyroidectomized woman had mild clinical hyperthyroidism and a diffuse goiter without exophthalmos. She complained of headaches and had bitemporal hemianopsia. Serum T4 and T3 by RIA were elevated, and TSH was 112 microU/ml (normal range, 1.1-7.2). The alpha-subunit to TSH molar ratio was 1.7 (normal, less than 1), as reported in other patients with tumoral TSH hypersecretion. After TRH, a marked increase in TSH occurred. There was no evidence of pituitary deficiency. Skull x-rays and computerized axial tomography revealed an intrasellar tumor with suprasellar extension. Selective transsphenoidal adenomectomy was performed, and a pituitary tumor was removed. The tumor was almost entirely composed of cells reactive with antihuman beta TSH serum by indirect immunofluorescence. A unique feature of this patient was the marked increase in TSH levels after L-dopa administration. To our knowledge, this paradoxical response has never been reported previously in such patients. Using [3H]domperidone as ligand, dopaminergic receptors were demonstrated in the membranes of the adenomatous thyrotroph cells. The reason for the paradoxical response of TSH to dopaminergic agents is not known.

Adenoma↗