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Biomedical subjects

J L Vandalem

Publications and source records attributed to J L Vandalem.

At least 19 recordsLinked to original sources
PubMed1991

Plasma thyrotropin concentration in the male pig: profile from birth to puberty and the effect of season and social environment in the young adult.

Plasma thyrotropin (TSH) secretion was studied in crossbred (Landrace x Large White) immature and young adult Landrace male pigs. Levels of TSH were low over the first 9 wk post-natally and were maximal at 12 wk of age. Thereafter, hormone levels declined and by 16 wk returned to values similar to those at 7 wk. In addition, a transient increase in TSH was noted at 22 wk. A second experiment involved 2 groups of young adult boars housed either in a socially non-restrictive environment (adjacent to estrual females) or a socially restrictive environment (not in direct physical contact with females). TRH stimulated secretion of TSH and the magnitude of this response was affected by month; minimum and maximum responses were found in May and August respectively. There was an effect of social environment on TRH-induced TSH secretion; during February and August, the magnitude of the TSH response to TRH was lower in socially restricted than in socially non-restricted boars.

Aging↗
PubMed1991

Thyrotropin-secreting pituitary adenomas: report of seven cases.

Seven patients with hyperthyroidism due to a TSH-secreting pituitary macroadenoma have been observed of a total of 800 patients with pituitary tumors over a period of 15 yr. Serum TSH levels varied between 1.1-36.3 mU/L. The serum alpha-subunit level was low in 1 case, while in 4 other cases the concentration was elevated and varied between 3.7-7.8 micrograms/L. Serum TSH beta levels were normal in the 4 cases in which it was determined. Serum GH or PRL levels were elevated in 5 cases. In 1 patient the cosecretion of TSH, GH, and PRL was confirmed by immunocytochemical examination. Serum TSH and alpha-subunit responses to TRH, GnRH, CRF, GRF, dexamethasone, methimazole, T3, and bromocriptine administration were variable when studied. Serum TSH and alpha-subunit circadian rhythms were absent in 1 case and inverted in another. A serum alpha-subunit pulsatility without TSH pulses was observed in 1 patient. Five patients underwent transsphenoidal adenomectomy. Three of 4 patients operated on in our center were cured, but a recurrence of the adenoma was found in 1 of them after 5 yr. The fifth patient was not cured. Treatment with octreotide in 3 patients resulted in normalization of serum TSH, GH, and thyroid hormones levels. Cosecretion of PRL in 1 case and alpha-subunit in 2 cases was also inhibited. Partial tachyphylaxis occurred in 1 patient. In summary, heterogeneity in clinical presentation, hormonal expression, and therapeutic response appears to characterize these TSH-secreting adenomas.

Adenoma↗
PubMed1987

Influence of age on pulsatile luteinizing hormone release and responsiveness of the gonadotrophs to sex hormone feedback in men.

The influence of aging on serum LH and testosterone (T) pulse frequency and gonadotroph sensitivity to androgen and estrogen feedback was studied in young (less than 55 yr old) and elderly (greater than 65 yr) Trappist monks. LH pulse frequency (sampling interval, 20 min) was significantly lower [0.25 +/- 0.03 (+/- SEM) vs. 0.38 +/- 0.02 pulses/h; P less than 0.01] in elderly (n = 21) than in young monks (n = 27); the pulse amplitudes were similar. Similarly, T pulse frequency was lower in the elderly than in the young monks (0.13 +/- 0.04 vs. 0.23 +/- 0.02 pulses/h; P less than 0.01). In elderly men, the hypothalamo-pituitary complex was more sensitive to 5 alpha-androstan-17 beta-ol-3-one feedback, as determined by the decrease in serum LH and T levels. Moreover, during 5 alpha-androstan-17 beta-ol-3-one (125 mg/day, percutaneously, for 10 days) administration, the LH response to LHRH (100 micrograms, iv) was significantly higher in the elderly men compared to the pretreatment response. During estradiol (1.5 mg/day, percutaneously for 10 days) administration, the LH response to LHRH was decreased in the elderly men, but unchanged in the young men, suggesting greater responsiveness to estradiol in the elderly men. We conclude that in aged men, decreased testicular androgen secretion is not exclusively the consequence of a primary testicular alteration, but that important changes occur in hypothalamo-pituitary function, specifically decreased LH pulse frequency and increased LH responsiveness to sex hormone feedback.

Adult↗
PubMed1986

Early normalization of luteinizing hormone pulsatility after successful transsphenoidal surgery in women with microprolactinomas.

In eight hyperprolactinemic amenorrheic women who had a microprolactinoma, LH secretion was examined by measuring its concentration in blood samples collected every 15 min for 6 h before and 8 days after successful selective adenomectomy. Computer analysis was used for LH peak evaluation. In both circumstances, serum PRL and basal estradiol (E2) levels were also determined. Before operation, the number of LH peaks ranged from zero to one per 6 h in seven patients and was two per 6 h in the eighth patient. In all patients, serum PRL was normal on the eighth postoperative day, while E2 levels remained low, similar to the values usually found in the early follicular phase of the cycle in normal women. Postoperatively, mean LH levels were similar to preoperative levels, but there was a dramatic increase in the number of LH peaks (three to five per 6 h) in five of the eight patients. These observations confirm the impairment of LH pulsatility in hyperprolactinemia and demonstrate that normalization of PRL levels by surgery can restore LH pulsatile secretion in certain women as early as the eighth day after operation in the absence of a significant change in serum E2 levels. Thus, the preoperative impaired pulsatility of LH secretion was probably a central effect of hyperprolactinemia.

Adenoma↗
PubMed1986

Ontogeny of hypothalamic pituitary function in the pig: pituitary thyrotrophin in the fetus and neonate.

Thyrotrophin in individual pituitaries obtained from fetal and prepubertal pigs was quantified by homologous radioimmunoassay (RIA) and heterologous radioreceptor assay (RRA). Relative evolution of pituitary TSH contents and concentrations with age were in good agreement as measured by both assay systems although the quantity of TSH detected by RRA appeared consistently lower than that measured by RIA. Thyrotrophin was first detected in pituitaries of fetal pigs at day 75 of gestation. Thereafter the pituitary content of TSH increased to approximately 45 micrograms/pituitary in the oldest group tested (6 weeks of age). The pituitary TSH concentration rose sharply until birth (114 +/- 1 day post coitum) and thereafter remained increased at a concentration of approximately 400 ng/mg wet weight.

Animals↗
PubMed1986

Developmental changes in gonadotrophins and testicular gonadotrophin receptors in the pig, from neonatal to adult life.

Changes in the concentrations of LH and FSH testicular receptors have been studied in the pig, from neonatal to adult life, and correlated with blood LH, FSH and testosterone concentrations. Quantification of gonadotrophin receptors was performed in equilibrium binding studies, using homologous systems. The presence of high-affinity binding sites for LH and FSH (association constant (Ka): LH approximately 20 litres/nmol; FSH approximately 10 litres/nmol) was demonstrated in the testes of all animals studied. The apparent affinity of LH and FSH receptors did not change significantly with age. During the first weeks of life, there was a transient rise in LH receptor content, reaching a maximum of 8.7 +/- 2.2 (mean +/- S.E.M.) pmol/g testis at 24 days of age. This was correlated with a peak in testosterone secretion and reflects the second wave of interstitial cell proliferation in the pig. A second increase in the number of LH receptors occurred after 12 weeks of age and corresponds to pubertal maturation and final differentiation of adult Leydig cells. During this period, circulating concentrations of testosterone markedly increased without any significant variation in LH blood levels, suggesting a change in testicular sensitivity to LH in the maturing pig. A continuous increase in FSH receptor content was observed from the neonatal to the adult pig. This increase occurred in two phases. During the first 2 months of life, the increase in the number of FSH receptors exceeded that of testis growth rate and resulted in an increase in FSH receptor concentrations which reached a peak at 12.1 +/- 1.8 pmol/g testis, at week 9.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

[Thyroiditis].

Explore the source record for details and available documents.

Adult↗
PubMed1985

The ontogeny of hypothalamic pituitary function in the pig. I. Pituitary LH and FSH in the fetus and neonate.

Pituitaries were collected from fetal and postnatal pigs from day 55 p.c. until 6 weeks after birth at closely spaced intervals. LH and FSH in individual pituitaries were quantified by both homologous RIA and homologous RRA. No significant difference was found between results obtained by RIA and RRA. Both LH and FSH are first detected by RIA and RRA in the porcine fetal pituitary at 75 days p.c. Thereafter both LH and FSH pituitary content rises until term. LH pituitary concentration in both male and female fetuses and FSH pituitary concentration in males exhibit a peak just before birth. FSH pituitary concentration in females rises until birth and thereafter remains elevated. A statistically significant sex difference was found postnatally with regard to FSH content and concentration but not for LH.

Animals↗
PubMed1981

Transient neonatal hyperthyrotropinemia: a factitious syndrome due to the presence of heterophilic antibodies in the plasma of infants and their mothers.

In a national screening program for neonatal hypothyroidism, our criterion for diagnosis is a plasma TSH value exceeding 40 microunits/ml on the fifth day of life. Excluding cases with obvious thyroid abnormalities, we identified a group of 14 neonates with unexplained plasma TSH elevation out of 10,261 screened. The mothers of these infants also exhibited high plasma TSH immunoreactivity; both mother and child in these instances were clinically euthyroid. The material responsible for this TSH immunoreactivity had the following characteristics. After parturition, it disappears from circulation within 2 months in the infants and within 4-6 months in the mother, its apparent molecular weight approximated 150,000 daltons, and its affinity for protein A-Sepharose and its binding properties suggested that the material was an immunoglobulin. Binding is observed typically for heterologous immunoglobulin and human TSH. The heterophilic character of these immunoglobulins explains their interference in many RIA systems, including the TSH RIA commonly used in neonatal screening programs for hypothyroidism.

Antibodies, Heterophile↗
PubMed1981

[Familial partial resistance to thyroid hormones. A report on one case (author's transl)].

Exploratory tests were conducted in a mother and her son presenting partial resistance to thyroid hormones. This resistance was best diminished by T3, but at the cost of very enhanced peripheral blood hormone levels, without clinical signs of hyperthyroidism. It is suggested that this resistance phenomenon is much more common than is generally accepted, but that it usually does not present the marked caricatural aspect as seen in the case reported.

Drug Resistance↗
PubMed1980

[Apparent transitory hyperthyrotropinemia of mothers and newborn infants related to the presence of maternal immunoglobulins].

Some newborns infants (screened for congenital hypothyroïdism) and their mothers were found to present an apparent isolated hyperthyrotropinemia. A large molecular size material (150 000 dalton) was found to carry the apparent immunoreactivity and was characterized as immunoglobulins, capable of binding TSH as well as Rabbit IgG. These maternal immunoglobulins are passively transferred to the newborn infants and interfere in various radioimmunoassays.

Animals↗
PubMed1979

Development and application of homologous radioimmunoassays for porcine gonadotrophins.

Antisera were raised against highly purified preparations of porcine luteinizing hormone (pLH) and follicle-stimulating hormone (pFSH). Highly specific and sensitive radioimmunoassay systems were developed. The antisera to LH and FSH were used at working dilutions of 1:500,000 and 1:200,000 respectively and the sensitivities of the assays were 0.1 ng LH/ml serum (3 x 10(-12) mol/l) and 0.5 ng FSH/ml serum (1.5 x 10(-11) mol/l). The LH and FSH preparations used as standards were 1.2 and 81 times as potent as NIH-LH-S15 and NIH-FSH-P1 respectively. Both assays were validated and adapted for the measurement of the gonadotrophin content of porcine serum. The concentrations of LH and FSH in blood were measured simultaneously in prepubertal sows throughout a 24 h period, in adult sows during the oestrous cycle and in both prepubertal and adult animals after treatment with LH releasing hormone.

Animals↗
PubMed1977

Thyroliberin and gonadoliberin tests during pregnancy and the puerperium.

Highly specific and sensitive radioimmunoassays for HTSH, HFSH and HLH have been used in order to investigate pituitary thyrotrophic and gonadotrophic functions of pregnant and puerperal women. The radioimmunoassay system for HFSH, using reagents prepared in our laboratory, is described. Thirty-three women were studied during pregnancy and post-partum. Forty-one TRH tests were performed. Basal levels of TSH, and increase in serum TSH after intravenous injection of TRH were similar in pregnant and puerperal women and in a control group. Thirty-three LH-RH tests were also performed. Basal levels of LH and FSH remained undetectable throughout pregnancy and in early puerperium. Furthermore, after intravenous injection of LH-RH neither LH nor FSH activity could be detected. It has thus been demonstrated that pituitary responsiveness to TRH during pregnancy and the puerperium is similar to that of non-pregnant young women. In contrast, a complete cessation of pituitary gonadotrophic functions is observed during the same period.

Adolescent↗