Recombinant human thyroid-stimulating hormone (Thyrogen) in thyroid cancer follow up: experience at a single institution.

BACKGROUND: Recombinant human thyroid-stimulating hormone (Thyrogen; Genzyme Corporation, Cambridge, MA, USA) (rhTSH)-stimulated serum thyroglobulin (Tg) (stim-Tg) and (131)I whole-body scanning (WBS) have been reported to allow follow up of patients with thyroid cancer without the symptoms of thyroxine withdrawal and with equivalent diagnostic information to that obtained after thyroxine withdrawal. The aim of the study was to report results of rhTSH use at the Alfred Hospital, Melbourne, from 1999 to 2006 and in particular to examine the significance of detectable serum Tg after rhTSH in relation to thyroid cancer staging and to compare the sensitivity of rhTSH-stimulated serum Tg to whole-body (131)I scanning (WBS) in the detection of residual and recurrent thyroid cancer. METHODS: The study was a retrospective chart review. RESULTS: In 90 patients, rhTSH was used for 96 diagnostic episodes and 18 doses of rhTSH were used to facilitate treatment with (131)I. In stages I and II cancer (n = 42), of three patients with stim-Tg 1-2 microg/L, none had identifiable disease, and the three patients who had stim-Tg >2 microg/L did not experience recurrent disease during follow up. In contrast, in stages III and IV cancer (n = 43) 2 of 5 with stim-Tg 1-2 microg/L had identifiable disease and 7 of 10 with stim-Tg >2 microg/L had identifiable disease. In Tg-positive, WBS-negative disease, further imaging identified persistent/recurrent disease. CONCLUSION: rhTSH was effective and safe in the management of thyroid cancer follow up for diagnosis of persistent/recurrent cancer and to enable (131)I treatment. In no case did rhTSH-stimulated WBS identify the presence of disease not also identified by raised basal Tg or stim-Tg. Therefore, in low risk cancer WBS may be omitted.

Reduced bone density in cystic fibrosis: DeltaF508 mutation is an independent risk factor.

The aim of this cross-sectional study was to determine the prevalence and identify determinants of reduced bone mineral density (BMD) in adults with cystic fibrosis (CF). Adults (88) with CF (mean+/-SD age 29.9+/-7.7 yrs; forced expiratory volume in one second (FEV1) 58.2+/-21.5% of the predicted value) were studied. BMD at the lumbar spine (LS) and femoral neck (FN) and body composition were measured using dual-energy X-ray absorptiometry. Blood and urine were analysed for hormones, bone turnover markers, and the cytokines tumour necrosis factor-alpha, and interleukin-6 and -1beta. FEV1 (% pred); CF genotype; malnutrition; history of growth, development or weight gain delays; and corticosteroid use were analysed. BMD Z-scores were -0.58+/-1.30 (mean+/-SD) at the LS and -0.24+/-1.19 at the FN. Z-scores of <-2.0 were found in 17% of subjects. Subjects who were homozygous or heterozygous for the DeltaF508 mutation exhibited significantly lower Z-scores than those with no DeltaF508 allele. Multiple linear regression showed that the DeltaF508 genotype and male sex were independently associated with lower BMD at both sites. Other factors also independently associated with lower BMD included malnutrition, lower 25-hydroxyvitamin D level, lower fat-free mass and lower FEV1 (% pred). In conclusion, reduced bone mineral density in cystic fibrosis is associated with a number of factors, including DeltaF508 genotype, male sex, greater lung disease severity and malnutrition.

Heterogeneity of amiodarone-induced thyrotoxicosis: evaluation of colour-flow Doppler sonography in predicting therapeutic response.

BACKGROUND: Amiodarone-induced thyrotoxicosis (AIT) presents a therapeutic challenge because of its resistance to standard antithyroid therapy. In iodine-deplete environments, colour-flow Doppler sonography (CFDS) has allowed distinction between two types of AIT: (i) Type I AIT, associated with increased vascularity (CFDS I-III) and response to thionamide antithyroid drug and (ii) type II AIT, with no/little thyroid vascularity (CFDS 0) and prednisolone responsiveness. AIM: To clarify if CFDS patterns correlated with treatment outcomes in a retrospective study of 24 patients with AIT in an iodine-replete environment. METHODS: Medical records of patients who presented to a teaching hospital between January 1998 to December 2000 were reviewed. Results of CFDS, ultrasound measurement of thyroid size and technetium scanning of the thyroid were correlated with treatment responses, especially prednisolone responsiveness. RESULTS: Thirteen of 24 patients showed CFDS 0. Twelve of these 13 were evaluable for prednisolone responsiveness, of whom seven (58%) were prednisolone-responsive. Of 11 patients with CFDS I-III, four (36%) responded to antithyroid medication alone and only one of seven (14%) was prednisolone-responsive. Euthyroidism was achieved twice as rapidly in patients with CFDS 0 than those with CFDS I-III. Because of medical treatment failure, seven patients, from both CFDS groups, required urgent near-total thyroidectomy which was successful and uncomplicated in all cases. CONCLUSIONS: CFDS is useful in the management of AIT because CFDS 0 correlates better with prednisolone response (58%) than CFDS I-III (14%). However, unlike experience in iodine-deficient regions, the results of the present study revealed that treatment responses to thionamide or prednisolone were heterogeneous within uniform CFDS patterns. Thus, prednisolone--responsiveness was not consistently predicted by CFDS 0, but the presence of flow appeared to correlate with non-response to prednisolone.

Modulation of T3-induced sex hormone-binding globulin secretion by human hepatoblastoma cells.

We have shown previously that tri-iodothyronine (T3)-induced sex hormone-binding globulin (SHBG) secretion by the human hepatoblastoma cell line, HepG2, can be modulated by retinoids. We have now used this model to study a range of other compounds that are known to influence T3 responsiveness in various cell systems. HepG2 cells were incubated for 4 days in serum-free medium containing T3, together with insulin, dexamethasone, phorbol myristate (PMA), sodium butyrate or estradiol. T3 (10 nmol/l) alone induced a concentration of SHBG secreted by HepG2 cells that was 187 +/- 20% (mean +/- S.D., n = 9) of control. Insulin (100 nmol/l) reduced basal SHBG secretion from 24.7 +/- 5.2 nmol/l to 16.1 +/- 1.7 nmol/l (P < 0.01). This effect was dose responsive, half-maximal at 3.4 +/- 3.0 nmol/l (approximately 600 mU/l) and maximal with 100 nmol/l insulin. Co-incubating 0-10 nmol/l T3 with 100 nmol/l insulin resulted in a downward shift in the dose-response curve without a change in the half-maximal response to T3. Conversely, 0-100 nmol/l insulin reduced SHBG production induced by 10 nmol/l T3. In contrast; while dexamethasone alone was without effect on SHBG secretion, 100 nmol/l dexamethasone induced a shift to the left in half-maximal T3 stimulation from 0.37 nmol/l to 0.10 nmol/l. The effect of PMA on SHBG secretion was reminiscent of the previously observed retinoid effect. PMA 100 nmol/l abolished maximal T3 stimulation. This effect was dose responsive, with a threshold at 1 nmol/l PMA. Sodium butyrate, up to 1 mmol/l was without effect; with greater concentrations, SHBG secretion was reduced. T3 responsiveness was virtually abolished by 3 mmol/l sodium butyrate; higher concentrations were cytotoxic and secretion was reduced to less than 20% of basal. Lack of an effect of estradiol on SHBG secretion by HepG2 cells was confirmed. These studies suggest that T3-induced SHBG secretion by HepG2 cells is independently influenced by insulin, potentiated by dexamethasone, and modulated by PMA. Detailed molecular analysis of this model will increase our understanding of the mechanism of action of T3, specifically in human liver cells.

Differential modulation of thyroid hormone responsiveness by retinoids in a human cell line.

Previous studies have suggested that there is an interrelationship between responses mediated by retinoic acid (RA) and those to thyroid hormone (T3). These experiments have used transfected gene constructs, often in receptor-negative cells. To study the relationship between RA- and T3-mediated responses in intact human cells, we incubated HepG2 cells for 4 days in serum-free medium with T3 and/or RA or 9-cis-RA. Measured responses were stimulation of secreted sex hormone-binding globulin (SHBG) or inhibition of secreted T4-binding globulin (TBG). T3 induced a dose-responsive increase in SHBG secretion that was maximal at 10nM (206 +/- 24% of untreated value) and half-maximal at 0.36 +/- 0.16 nM T3. RA and 9-cis-RA, up to 100 nM, induced a slight fall in SHBG secretion to 79 +/- 9% and 88 +/- 9%, respectively. T3 induction of SHBG secretion was significantly attenuated in cells coincubated with T3(0-10nM) and RA. With T3 (10 nM) together with RA (3, 10, or 100 nM), the maximal SHBG responses were reduced to 193 +/- 24%, 151 +/- 5% and 132 +/- 30%, respectively. With T3 and 9-cis-RA (100 nM), maximal stimulation was 169 +/- 20%. Importantly, the effective half-maximal stimulatory concentration of T3 in the presence of either retinoid (3-100 nM) was unchanged at 0.3 nM T3. In addition, the inhibitory effect of 9-cis RA could not be overcome even with 300 nM T3. The threshold for the RA effect was between 0.3-1 nM, with half-maximal inhibition at 30 nM. 9-cis-RA was approximately 10-fold less potent than RA. Preliminary studies suggested that changes in SHBG messenger RNA levels were similar to those in secreted SHBG. No effect was observed with vitamin D or clofibrate, either alone or combined with T3. Conversely, T3 reduced TBG secretion, with maximal suppression to 74 +/- 5% of the control value at a T3 concentration of 10 nM. RA alone reduced TBG secretion to 76% of the control value. RA did not attenuate the effect of T3, and the two agents combined showed no synergism. Neither T3 nor RA, alone or in combination, influenced secreted total protein or albumin. RA did not alter the concentration of nuclear T3-binding sites. These data suggest that retinoids act via a gene-dependent mechanism to modulate maximal, but not half-maximal, responses to T3 in HepG2 cells with the specificity of RA greater than that of 9-cis-RA.

Preferential inhibition of cytoplasmic T3 binding is associated with reduced nuclear binding in cultured cells.

Previous studies from our laboratory have suggested that the nonsteroidal antiinflammatory drug, diclofenac (DCF), is a more potent competitor for T3 binding sites in cytoplasm than for those in the nucleus. In the present study we have examined the competitive potency for DCF and its effect on nuclear binding of T3 in cultured cells. DCF was a weak competitor for T3 binding sites in cytosol and nuclear extracts prepared from HepG2 cells with a potency of 21 and 295 microM, respectively. When expressed relative to T3, DCF was 135-fold more potent in cytosol than in nuclear extract. In intact cells, T3 was bound by nuclei with an affinity, Kd of 0.22 +/- 0.07 nM whereas in nuclear extract the affinity was 0.60 +/- 0.21 nM. DCF was a competitive inhibitor in both preparations but reduced the apparent affinity 4-fold in intact cells but only 2-fold in nuclear extract. In whole-cell experiments, DCF increased the rate of dissociation of T3 from cells prelabeled with hormone for 30 min. When these prelabeled cells were incubated with DCF, 0.1 mM, cell-associated T3 was significantly lower at 30 and 60 min than in cells reincubated without the drug. These data show that cellular transport mechanisms precede nuclear binding by T3 and suggest that there is a critical role for nonnuclear binding proteins in thyroid hormone action.

Drug effects on triiodothyronine uptake by rat anterior pituitary cells in vitro.

In nonthyroidal illness, numerous drugs such as glucocorticoids, dopamine, fenclofenac, furosemide and diphenylhydantoin may modify the close inverse-feedback relationship between circulating thyroid hormones and TSH. Such effects could involve altered hypothalamic TRH secretion, a direct effect on TSH production by the thyrotroph, alterations in circulating free thyroid hormone concentrations, or changes in thyroid hormone uptake by the thyrotroph. We therefore examined the effect of nonsteroidal antiinflammatory drugs (NSAID), diuretics, the synthetic flavonoid EMD 21388, and diphenylhydantoin, on [125I]T3 cellular uptake in rat pituitary primary cell cultures. Uptake of [125I]T3 (cell-associated counts of washed cells) was measured at 15 min after the addition of 50 pmol/L [125I]T3 in protein-free medium (37 degrees C, pH 7.4). Uptake of [125I]T3 by pituitary cells was 6.0 +/- 1.7% of total counts (mean +/- SD, n = 18). Unlabeled T3 (10 mumols/L) displaced 92% of total uptake. The IC50 of unlabeled T3 for the displacement of [125I]T3 was 1.2 mumols/L. T4 and rT3 were approximately 10% as effective as T3 itself in inhibiting [125I]T3 uptake, while triac did not affect cellular [125I]T3 uptake. Inhibition of [125I]T3 uptake at drug concentrations of 100 mumols/L was seen with the diuretics, furosemide (9%), bumetanide (14%), piretanide (12%) and ethacrynic acid (76%), the NSAID, meclofenamic acid (35%) and fenclofenac (52%), EMD 21388 (49%), and the anticonvulsant, diphenylhydantoin (23%). Aspirin, up to 500 mumols/L, had no effect on [125I]T3 uptake. Our results indicate that ethacrynic acid, meclofenamic acid, fenclofenac, EMD 21388 and diphenylhydantoin affect plasma membrane T3 uptake in the pituitary. This potential influence on TSH release will be contrary to the previously-demonstrated direct inhibitory effect of these drugs on TSH release.

A prospective audit of total parenteral nutrition at a major teaching hospital.

OBJECTIVE: To examine patterns of use and clinical outcomes of total parenteral nutrition (TPN). DESIGN: A prospective six-month audit (December 1992-June 1993). PATIENTS AND SETTING: All inpatients administered TPN at a metropolitan teaching hospital during the audit period. MAIN STUDY MEASURES: Process measures included data about TPN initiation (bodyweight, period not receiving oral/nasogastric feeding, serum albumin level, compliance with hospital guidelines), TPN delivery data (kilojoules, and nutrient and electrolyte content), and bases for cessation or changes of TPN (biochemistry data, gastric and intestinal function). Outcome measures included body mass change, infection rate, detection of biochemical abnormalities, and death. RESULTS: During the audit 168 consecutive patients received 175 TPN courses. These patients were followed until discharge or death; 49 patients (29%) died. Intensive care units accounted for 57.7% of TPN use. Deviations from approved hospital guidelines for initiation of TPN were common. Only a minority of patients were malnourished on objective audit criteria; 18% of men and 13% of women were underweight by body mass index criteria and 36% were malnourished when serum albumin level (< 30 g/L) was considered. Early initiation of TPN outside accepted guidelines was common. Complications included bacteraemia (9.1% of patients tested) and catheter-tip sepsis (55.2% of 87 catheters tested). Four patients died; line sepsis caused one death and probably a further two. The incidence of glucose intolerance was 36.5%, and 25% had markers of abnormal liver function. CONCLUSIONS: TPN use is associated with a high risk of morbidity, and a 1.7% mortality. We recommend better patient selection for TPN, more appropriate use of enteral feeding, better infection control procedures, avoidance of substrate overload (particularly glucose), and earlier change to enteral nutrition.

Effect of loop diuretics and nonsteroidal antiinflammatory drugs on thyrotropin release by rat anterior pituitary cells in vitro.

The close inverse-feedback relationship between serum free thyroxine (T4) and thyrotropin (TSH) is altered in some patients receiving therapeutic doses of drugs such as furosemide, fenclofenac, and diphenylhydantoin. We therefore examined the effect of nonsteroidal antiinflammatory drugs (NSAID), diuretics, and diphenylhydantoin on TSH release in rat anterior pituitary cells in primary culture. TSH content of the culture medium was measured at 22 hours at 37 degrees C either with or without thyrotropin-releasing hormone ([TRH] 10 nmol/L) in medium containing 0.5% bovine serum albumin. The mean basal TSH release by pituitary cells was 6.2 +/- 1.2 ng/mL (n = 10) and was not influenced by unlabeled triiodothyronine ([T3] 100 nmol/L) or any of the drugs tested at < or = 400 mumol/L, except ethyacrynic acid. TRH 10 nmol/L increased mean TSH release by 346% +/- 95% (n = 10). T3 1 and 100 nmol/L inhibited TRH-stimulated TSH release by 24% and 31%, respectively (P < .001), whereas TRH-stimulated TSH release was inhibited by 100 mumol/L meclofenamic acid (29%), fenclofenac (28%), furosemide (24%), and diphenylhydantoin (48%) (P < .001 v TRH alone). Meclofenamic acid and furosemide (100 mumol/L) did not significantly alter the inhibitory effect of T3 1 nmol/L on TRH-stimulated TSH release. These in vitro studies suggest that meclofenamic acid, fenclofenac, furosemide, and diphenylhydantoin could influence TSH release by attenuating the TSH response to TRH. This effect may influence T4-TSH relationships when these agents are used in vivo.

Influence of nonesterified fatty acids and lysolecithins on thyroxine binding to thyroxine-binding globulin and transthyretin.

The hydrolysis of lecithin by phospholipase produces equimolar amounts of nonesterified fatty acids (NEFAs) and lysolecithin. In this study, we have evaluated the effect of lysolecithins and NEFAs on thyroid hormone binding by examining their interactions with thyroxine-binding globulin (TBG)(serum 1:10,000 dilution) and purified transthyretin (TTR). Unsaturated NEFAs (palmitoleic, oleic, linolenic, arachidonic, eicosapentaenoic, and docosahexaenoic acid) inhibited [125I]T4 binding to TBG. Their affinities, relative to unlabeled T4, ranged from 0.005 to 0.0016%, except for oleic acid with relative affinity of < 0.0005%. Saturated NEFAs, lauric, myristic, palmitic, and stearic acid were inactive. After purification by high-performance liquid chromatography, 1-oleoyl and 2-oleoyl lysolecithin displaced [125I]T4 from TBG with an affinity of 0.0006 and 0.0005%, respectively. On a molar basis, this affinity was approximately 10-fold lower than arachidonic acid, the most potent NEFA in inhibiting T4 binding to TBG in this assay system. Of all the NEFAs tested, only arachidonic acid inhibited [125I]T4 binding to TTR, with an affinity relative to unlabeled T4 of 0.49%. 1-Oleoyl, 1-palmitoyl, and 1-stearoyl lysolecithin were without effect on TTR binding. The T4-displacing effects of NEFAs are markedly attenuated by their extensive binding to albumin. Using purified [14C]NEFA preparations and heptane partitioning, the mean unbound percentages of linoleic, eicosapentaenoic, and docosahexaenoic acid in undiluted normal human serum were 0.00099, 0.0050, and 0.0042%, respectively (n = 3). In view of the very high degree of albumin binding of NEFAs, studies in diluted serum will grossly overestimate their competitor potency. The affinities of lysolecithins for the T4 binding sites of TBG and TTR are lower than those of NEFAs and depend on the fatty acid component. Lysolecithins are unlikely to influence plasma protein binding of T4 during critical illness.

Down-regulation of thyroxine-binding globulin messenger ribonucleic acid by 3,5,3'-triiodothyronine in human hepatoblastoma cells.

A sensitive [125I]-T4 binding assay was used to measure serum T4-binding globulin (TBG) in 60 individuals selected on the basis of their total circulating T3 concentrations, and a relationship between TBG and circulating thyroid hormone levels in humans was confirmed. There was a significant correlation between serum TBG and T3 or free T4 index. TBG secretion and TBG messenger ribonucleic acid (mRNA) production were studied with a continuous culture of the human hepatoblastoma cell line, HepG2. Cells were maintained in serum-free media for experimental manipulations. The addition of 100 nmol/L T3 to the cell medium resulted in a time-dependent down-regulation of TBG mRNA to 33 +/- 6% (+/- SD, n = 4) of untreated control levels by 24 h. Suppression of TBG mRNA was first detectable at 8 h (57% of untreated control levels). The effect of T3 was dose-responsive, with half-maximal suppression of TBG mRNA occurring at a bioavailable T3 concentration of approximately 30 pmol/L. The effect of T3 on TBG mRNA was not caused by a change in mRNA stability. Proteins secreted by HepG2 cells bound T4 with an affinity identical to that of normal circulating TBG. Cell secretion of TBG was parallel to total protein secretion and consistent with a TBG secretion rate of 50 ng/10(6) cells per day. Variations in the concentration of secreted binding protein in the presence of T3 corresponded to the changes observed in TBG mRNA. These data show that circulating TBG concentration is negatively correlated with total serum T3 in vivo. The corresponding down-regulation observed between TBG mRNA and secreted protein in HepG2 cells suggests that this effect is the result of the action of T3 on cellular TBG mRNA synthesis.

Specific effects of radioiodine treatment on TSAb and TBAb levels in patients with Graves' disease.

Radioactive iodine (RAI)-induced changes in the levels of antibodies to the thyroid-stimulating hormone (TSH) receptor (TRAb) in patients undergoing treatment for autoimmune thyroid disease have been well documented. Previous studies have reported effects on the overall level of the antibodies present, TSH-binding inhibitory immunoglobulins (TBII), without detailed studies of specific effects on the levels of thyroid-stimulating (TSAb) or thyroid-blocking antibodies (TBAb). More detailed studies have been reported only in individual cases. In this study, the values of TSAb, TBAb, and TBII were measured longitudinally in 33 patients (27 females and 6 males) who received RAI. The bioassays for TSAb and TBAb were performed in JPO9 cells. Following RAI, there were significant and immediate effects on the values of TBII in 70% of patients. TBII levels fell in 7 patients (20%) (Group 1), rose in 16 patients (48%) (Group 2) or remained unchanged but elevated in 10 patients (32%) (Group 3). In the Group 1 patients, only TSAb were detectable and none of these patients became hypothyroid after treatment. In the 16 patients in Group 2, increases in TBII were attributable to specific increases in TSAb in 7 (44%), in TBAb in 3 (19%), and in both TSAb and TBAb in 3 (19%). There were 3 patients (19%) in this group in whom there was no detectable TSAb or TBAb activity despite the increase in TBII. Six patients from this group became hypothyroid within 6 months of RAI treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug competition for intracellular triiodothyronine-binding sites.

A variety of substances, including frusemide, non-esterified fatty acids (NEFAs) and non-steroidal anti-inflammatory drugs (NSAIDs), can compete for triiodothyronine (T3)-binding sites in serum and at the cell surface. We examined the competitive potency of these agents at intracellular T3-binding sites in order to assess their potential to act as T3 antagonists. Competition for [125I]T3 binding was determined using hydroxyapatite separation in cytosols and nuclear extracts prepared from livers of Macaca fascicularis. The T3 affinities were 15.8 +/- 1.2 nmol/l in cytosol and 0.23 +/- 0.02 nmol/l in nuclear extract. Dose-response curves were analysed by a four-parameter sigmoid curve-fitting program to determine competitor potency. The nineteen agents tested included various NSAIDs, NEFAs, non-bile acid cholephils (NBACs), frusemide, amiodarone and the flavonoid EMD 21388. In nuclear extract the most active competitors were linoleic acid (8.5 mumol/l) and linolenic acid (7.8 mumol/l). Potencies of NSAIDs varied between 66 mumol/l (meclofenamic acid) and 525 mumol/l (diclofenac). In cytosol, NEFAs were less potent but NSAIDs were stronger competitors than in nuclear extract. Half-inhibitory potencies in cytosol were between 13.2 mumol/l (meclofenamic acid) and 63.1 mumol/l (flufenamic acid). The NBAC bromosulphthalein was one of the most potent inhibitors in both cytosol and nuclear extract. When expressed relative to T3, diclofenac was a more effective competitor in cytosol than it was in nuclear extract. Amiodarone and EMD 21388 were without effect both in cytosol and nuclear extract. Frusemide (759 mumol/l) was weakly active in cytosol only.(ABSTRACT TRUNCATED AT 250 WORDS)

Thyroxine binding by human transthyretin variants: mutations at position 119, but not position 54, increase thyroxine binding affinity.

A mutation at codon 119 in the transthyretin (TTR) gene leads to a substitution of methionine for threonine at this position in the circulating protein. As the amino acid at position 119 is located in the T4 binding channel, mutations here may affect the binding of T4 by TTR. A previous study has shown an increase in the amount of hormone carried by the TTRMet119 variant. To determine whether this increase in binding was due to a change in affinity or capacity, TTR was partially purified from normal individuals and those with the TTRMet119 mutation. The isolation procedure was a rapid, single step passage through Blue Sepharose. With normal serum, the resulting protein bound T4 with a single site of intermediate affinity (Ka, 1.63 +/- 0.36 x 10(7) L/mol). No sites of higher or lower affinity were detected. Comparisons of binding capacity and immunoreactive TTR concentrations showed that the preparations bound T4 with a molar ratio between 1-2. With TTRMet119 serum, the T4 affinity was approximately doubled [Ka, 3.40 +/- 0.76 x 10(7) L/mol (+/- SD); P < 0.001] with no change in binding capacity. This doubling in affinity explains the observed T4 levels of about 120 nmol/L in individuals with this mutation. Binding of rT3 to TTRMet119 was increased approximately 5-fold over normal. Identical experiments with TTRGly54, in which glycine is substituted for glutamine, showed that the T4 affinity of this variant was unchanged from normal. These results suggest that the TTRMet119 mutation leads to secretion of a normal concentration of TTR that has a raised affinity for T4. Depending on their location, mutations in the TTR gene may lead to an increase or no change in T4 binding by the secreted protein.

Stimulation of sex hormone-binding globulin mRNA and attenuation of corticosteroid-binding globulin mRNA by triiodothyronine in human hepatoma cells.

We examined the time course and dose response of the triiodothyronine (T3) effect on mRNAs for sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) in cells of the human hepatoma line HepG2. After 7 h of exposure to a saturating dose of T3, SHBG mRNA was unchanged but increased to 1.5 +/- 0.1 times the unstimulated control at 22 h. Maximal stimulation (2.3 +/- 0.6) was observed at 2-3 days. Corticosteroid-binding globulin mRNA was unchanged for 22 h after exposure to T3 but diminished thereafter to 64% by day 3. At 3-4 days of exposure, the changes in both SHBG mRNA and CBG mRNA were dose-responsive to the T3 concentration. For both mRNAs, half-maximal response occurred between 10 and 20 pmol/l bioavailable T3. Cortisol-binding proteins secreted by HepG2 cells after 3 days in culture also were T3 dose-responsive. No re-uptake of secreted CBG by the cells was observed, suggesting that the T3 effect on CBG secretion occurs during production of the mature protein. These data suggest that T3 stimulates the expression of the SHBG gene and attenuates the expression of the CBG gene. The effects of T3 on these genes are consistent with the increase in circulating SHBG and decrease in circulating CBG observed in hyperthyroidism. The HepG2 cells may be a useful human cell line in which to study the diversity of the molecular mechanisms of T3 action.

Single anticardiolipin measurement in the routine management of patients with systemic lupus erythematosus.

OBJECTIVE: To examine the usefulness of a single measurement of anticardiolipin antibodies (aCL) in systemic lupus erythematosus (SLE) in routine clinical practice. METHODS: All 127 patients with SLE currently followed by our rheumatology unit had an aCL measurement on routine clinic review. Their charts were then reviewed for specific disease manifestations. Basic statistical correlations of the aCL result and the specific disease manifestations were performed, and the clinical utility of the aCL test assessed using Bayesian analysis. RESULTS: aCL was positive (> 2 SD) in 24% and was associated with recurrent fetal loss, thrombosis, cerebrovascular disease, livedo reticularis and digital infarcts. Bayesian analysis showed that a single positive aCL test increased the relative and absolute risk of all the above complications. The criterion of aCL positivity as > 15 units (2 SD) was associated with the highest relative risk. CONCLUSION: A single positive aCL test in routine management of SLE is a useful predictor of important clinical events.

A naturally occurring furan fatty acid enhances drug inhibition of thyroxine binding in serum.

We studied the thyroxine (T4)-displacing effects of a naturally occurring, highly albumin-bound furanoid acid that accumulates in serum in renal failure to concentrations in excess of 0.2 mmol/L. This substance, 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF), has been shown to displace acidic drugs from albumin binding. The effects of CMPF on ligand binding were assessed in the following systems: (1) T4 binding to T4-binding globulin (TBG) and transthyretin (TTR), (2) T4 binding in undiluted serum, (3) T4-displacing potency of fenclofenac, furosemide, diflunisal, and aspirin in undiluted serum, (4) serum binding of [14C]-drug preparations, and (5) serum binding of [14C]-oleic acid. CMPF had a minor direct effect on T4 binding to TBG comparable in relative affinity to that of aspirin, ie, almost 7 orders of magnitude less than T4 itself. CMPF alone at a concentration of 0.3 mmol/L, which produced only a 10% to 14% increase in free T4 augmented the T4-displacing effects of high therapeutic concentrations of the various drugs in undiluted serum as follows: furosemide by 180%, fenclofenac by 160%, diflunisal by 130%, and aspirin by 40%. In the presence of fenclofenac, increments of CMPF from 0.075 to 0.3 mmol/L progressively augmented the T4-displacing effect of this drug, associated with a progressive increase in its calculated free concentration. CMPF also inhibited the binding of [14C]-oleic acid, suggesting that in some situations CMPF could also indirectly influence thyroid hormone binding by increasing the unbound concentration of nonesterified fatty acids (NEFA), as previously described.(ABSTRACT TRUNCATED AT 250 WORDS)

Naloxone stimulation of ACTH secretion during petrosal sinus sampling in Cushing's syndrome.

1. Petrosal sinus sampling has been used to establish the source of adrenocorticotropin (ACTH) in ACTH-dependent Cushing's syndrome. Naloxone, an opioid antagonist, stimulates ACTH secretion, probably via release of endogenous hypothalamic corticotropin releasing hormone (CRH). 2. Three patients with hypercortisolism were studied. Two showed suppressed (> 50%) urinary-free cortisol excretion with high-dose dexamethasone treatment (2 mg every 6 h for 2 days), one did not suppress. The patients were subjected to bilateral simultaneous inferior petrosal sinus sampling (BSIPSS) with simultaneous peripheral venous (forearm) samples. Basal (unstimulated) samples were taken and naloxone (125 micrograms/kg bodyweight) was given intravenously with subsequent simultaneous sampling. Plasma ACTH was measured by radio-immunoassay (RIA). 3. All cases exhibited a marked rise in immunoreactive (IR)-ACTH levels (pmol/L) after naloxone injection, basal to peak: case 1, left 11.5-22.1, right 9.8 with no rise, peripheral 9.1-9.5; case 2, left 456-863, right 125-501, peripheral 59-82; case 3, left 12.7-13.0, right 277-431, peripheral 12.1-11.7. All results indicate pituitary Cushing's syndrome, with a central to peripheral ratio > 2.3:1. Pituitary Cushing's syndrome was confirmed on the results of trans-sphenoidal pituitary surgery in cases 1 and 3. 4. It is suggested that naloxone injection during petrosal sinus sampling in Cushing's syndrome may assist in the diagnosis of ACTH source, by enhancing ACTH release from a pituitary micro-adenoma.