Evidence of hyperthyroidism in apparently euthyroid patients treated with levothyroxine.

A concentration of serum thyroxine (T4) above the accepted normal range has recently been recognized to result from commonly prescribed replacement dosages of levothyroxine sodium. To determine if the high levels of serum T4 have undesirable metabolic effects, despite the fact that the subjects are accepted as euthyroid, we studied 28 patients receiving long-term levothyroxine therapy; 19 patients were considered to be receiving replacement dosages and nine suppressive dosages of levothyroxine. To assess the effect of levothyroxine on target tissue, we measured the thyrotropin response to protirelin and systolic time intervals obtained by simultaneous electrocardiography and echocardiography. Thyrotropin response to protirelin was suppressed in patients with elevated serum T4 levels and normal serum triiodothyronine levels. These patients also had shortened systolic time intervals typical of hyperthyroidism. Our data indicate that commonly given replacement dosages of levothyroxine may induce undesirable metabolic consequences and that these patients perhaps ought to be seen as having "subclinical hyperthyroidism." The prescribed dosage of levothyroxine as therapy for hypothyroidism is still frequently excessive.

Alterations in thyroxine metabolism produced by cutaneous application of microscope immersion oil: effects due to polychlorinated biphenyls.

A 30% solution of a polychlorinated biphenyl (PCB) mixture or a microscope immersion oil containing 34% PCB, when applied to the skin of rats, led to substantial increases in the biliary excretion of intravenously injected [125I]thyroxine (T4) in bile: plasma 125I ratios, in the biliary clearance rate of plasma [125I]T4, and in bile flow. Both PCB preparations also elevated liver weight, thyroid 125I uptake, and Sephadex uptake of [125I]triiodothyronine (T3), and depressed serum T4 concentrations; serum T3 levels were unaltered by the PCB solution or by the immersion oil containing PCB. PCB, either in mineral or immersion oil, reduced the free T4 index (serum T4 X fraction Sephadex T3 uptake), indicating a probable reduction in the concentration of free T4 in serum; the free T3 index, on the other hand, was elevated in PCB-treated rats. The same type of immersion oil, in which the PCB was replaced by a hydrogenated terphenyl, was without effect on any of the indices studied. Thus, the effects of microscope immersion oil on T4 metabolism were due to its PCB content. In thyroidectomized, T4-maintained rats, PCB in mineral oil again increased Sephadex uptake of [125I]T3, greatly reduced serum T4, and moderately reduced serum T3 levels; the free T4 index was substantially reduced and the free T3 index moderately lowered in treated animals. These data indicate that in PCB-treated rats both the peripheral conversion of T4 to T3 and thyroid T3 secretion were enhanced. The metabolic impact of thyroid hormone in PCB-treated animals was unchanged, as shown by normal activity of hepatic mitochondrial L-alpha-glycerophosphate dehydrogenase.

Hypothyroidism-induced changes in triiodothyronine binding to nuclei and cytosol-binding proteins in rat liver.

A tracer dose of [125I]T3 was given iv to normal, thyroidectomized, and propylthiouracil-fed rats and the distribution of radioactivity in serum and liver fractions was studied over 1 h. Total liver homogenate and serum 125I were higher at all times in hypothyroid rats and, in all groups, showed a continuous fall over the period studied. Hepatic nuclear 125I was maximal at 20 min in all and was greater in hypothyroid rats; there was more 125I in the hepatic cytosol of normal rats than in that from either thyroidectomized or propylthiouracil-fed animals. Binding studies with [125I]T3 and purified hepatic neclear preparations in vitro indicated that both the association constant, Ka (1.08-9.0 x 10(9) M-1) and the capacity (500-600 pg/mg DNA) in thyroidectomized and goitrogen-treated rats were similar to those obtained with normal animals. Cytosol, on the other hand, showed a decrease in binding capacity without change in affinity in livers of hypothyroid rats. Analysis of binding data by Hill plots indicated the presence of both positive and negative cooperativity in binding of T3 by rat liver cytosol proteins. In the in vitro experiments, higher serum radioactivity alone could not account for increases in the hepatic nuclear 125I in the hypothyroid rats because cytosol 125I (presumably in dynamic exchange with both blood and nuclei) was less. Consequently, cytosol T3-binding proteins may regulate the free T3 concentration in the cell and, thus influence the distribution of the hormone in other cellular compartments.

Absence of thyroid-stimulating antibody and long acting thyroid stimulator in relatives of Graves' disease patients.

None of the 76 euthyroid relatives of patients with Graves' disease had detectable LATS in their serum nor was thyroid-stimulating antibody (TSAb), assessed by an increment of cAMP in human thyroid slices, detected in any of the 60 sera tested. Seven of 41 were slightly positive for TSH binding-inhibiting immunoglobulin (TBII). Nineteen of 73 sera were positive (greater than 1:1600) for antibody to thyroid antimicrosomal antigen, of which 4 were also positive (greater than 1:400) for antibody to thyroglobulin; 3 of the 19 had a slightly elevated basal TSH which rose excessively after TRH. Thus, although these euthyroid relatives had evidence of thyroid immunological defects, a thyroid-stimulating antibody was not found.

Triiodothyronine (T3) nuclear binding sites in human placenta and decidua.

We studied the binding of triiodothyronine (T3) to human placenta and decidua. Although the placenta effectively blocks transfer of thyroxine (T4) and T3 it may itself be a thyroid hormone-dependent tissue and may specifically bind T3. A single class of high-affinity binding sites was found (Ka 3.8 +/- 0.31 s.e.m., and 3.3 +/- 10(9) M-1) for both placenta and decidua. Limited capacity was also observed, viz., 0.117 +/- 0.01 and 0.102 +/- 0.018 fmoles/microgram deoxyribonucleic acid (DNA), respectively. Endogenous T3 nuclear saturation was 34 per cent. Our results are consistent with the proposal that placenta and decidua have similar T3 specific nuclear binding sites and that T3 may have a direct action in the placenta.

Morphologic and metabolic changes in rat osteoblast cultures during the dark reaction with 8-methoxypsoralen.

The dark reaction of 8-methoxypsoralen (8-MOP) with cultured rat osteoblasts did not cause significant changes in cellular replication rates or in the synthesis of RNA and proteins. Microscopic examination, however, revealed that the dark reaction resulted in massive accumulation of perinuclear lipids and in the statistically significant enhancement of alkaline phosphatase activity. A sharp, and statistically significant, upsurge of lipid synthesis in osteoblasts preceded microscopically detectable accumulation of lipids and occurred only during the initial, but not during the subsequent stages of the dark reaction. These results suggest that in the course of the dark reaction the plasma membrane of osteoblasts is a target of psoralen.

Gentamicin penetration into normal rabbit nucleus pulposus.

STUDY DESIGN: Radioactively labeled gentamicin was administered to 24 rabbits to assess the concentration of antibiotic in the nucleus pulposus. OBJECTIVES: The purpose of the study was to investigate the pharmacokinetics of gentamicin penetration into normal rabbit nucleus pulposus. SUMMARY OF BACKGROUND DATA: Disc space infection is a complication of spinal surgery that can be prevented by prophylactic antibiotics. Gentamicin can be used in conjunction with other antibiotics as a prophylactic agent. One previous study demonstrated that a similar antibiotic, tobramycin, penetrates the disc, but no data have been reported on the pharmacokinetics of disc penetration. METHODS: Twenty-four rabbits were given an intravenous injection of gentamicin labeled with iodine 125. Four rabbits were killed at hourly intervals 1 to 6 hours after injection. Specimens of nucleus pulposus, blood, whole liver, and saline-perfused liver were obtained and prepared. The radioactivity in the specimens was measured. RESULTS: The gentamicin concentration in the nucleus pulposus peaked at 2 hours and remained at this level for the duration of the experiment. Twenty percent of the gentamicin recovered from the nucleus pulposus was tissue bound. CONCLUSIONS: Gentamicin concentration in the rabbit nucleus pulposus does not peak until 2 hours after an intravenous bolus of drug. If gentamicin penetrates human nucleus pulposus in a similar fashion, this study could have implications for the timing of administration of this agent for prophylaxis.

Tissue distribution of antibiotics in the intervertebral disc.

STUDY DESIGN: This study analyzed the distribution of antibiotics within the intervertebral disc of rabbits. Specimens were tested with specific antibodies against antibiotics using an immunofluorescent technique. OBJECTIVES: The results were correlated to provide a rationale for perioperative prophylaxis of infection. SUMMARY OF BACKGROUND DATA: Several groups of investigators and the recent data from our laboratory showed quantitative changes in penetration of antibiotics into intervertebral disc. No previous study has assessed antibiotic distribution in anulus fibrosus and nucleus pulposus. METHODS: Discs were obtained from rabbits after intravenous injection of penicillin or gentamicin. Antibiotics were localized in tissue sections using specific antibodies with a immunofluorescent method. RESULTS: Penicillin (negatively charged) and gentamicin (positively charged) penetrated the neutrally charged anulus fibrosus, but penicillin had less ability than gentamicin to penetrate into the negatively charged nucleus pulposus. CONCLUSION: Our data suggest that penetration and distribution of antibiotics into avascular intervertebral disc is significantly influenced by the charge of antibiotics.

Penetration of glycopeptide antibiotics in nucleus pulposus.

The penetration of the glycopeptide antibiotics vancomycin and teicoplanin into the nucleus pulposus of rabbits was studied. Blood samples were obtained at 0.5, 1, 4, 8, and 24 hours after intravenous administration of 30 mg/kg vancomycin or 16 mg/kg teicoplanin. Concentrations of antibiotics were determined in tissue specimens and serum samples by fluorescence polarization immunoassays. Antimicrobial activity in the nucleus pulposus was determined with an agar diffusion method using a strain of Micrococcus luteus as the indicator organism. A peak concentration of vancomycin in the nucleus pulposus was attained 8 hours after drug administration. Teicoplanin reached its maximum level and plateaued 1 and 2 hours, respectively, after injection, and it remained unchanged for the rest of the study. This microbiologic analysis showed that the nucleus pulposus contained an antimicrobial level of glycopeptide antibiotics after administration. Because rabbit nucleus pulposus is similar anatomically to that of humans, these results may have implications regarding the timing and choice of antibiotic administration.

Evaluation of serum osteoblast mitogenic activity in spinal cord and head injury patients with acute heterotopic ossification.

STUDY DESIGN: This was a blind, prospective study of the effect of sera from patients with spinal cord and head injuries on osteoblast proliferation. OBJECTIVES: The authors studied whether a humoral factor that stimulates the formation of heterotopic bone is released into the circulation after a neural injury. BACKGROUND DATA: Other authors have shown that a humoral osteoinductive factor may be released after head and spinal cord injuries. METHODS: Serum was obtained at certain times throughout the first 12 weeks post-injury and from control subjects. It was incubated with osteoblasts harvested from fetal rats, as well as with fibroblast controls. RESULTS: There was a significant rise in serum mitogenic activity after injury in both groups. When patients that developed heterotopic ossification were compared to other patients and controls, no significant differences were seen. CONCLUSIONS: This in vitro study fails to support a humoral mechanism for heterotopic ossification after spinal cord or brain injuries.

Effect of nonsteroidal antiinflammatory drugs on fracture healing: a laboratory study in rats.

We studied the effects of two nonsteroidal antiinflammatory drugs (NSAIDs) on fracture healing in rats: ibuprofen (30 mg/kg/day) and indomethacin (1 mg/kg/day). Femoral fractures were induced via a three-point bending technique. NSAIDs were administered orally for 4 or 12 weeks. Control animals received no medication. In each group a minimum of six animals were killed at the following intervals: 2, 4, 6, 8, 10, and 12 weeks postfracture. Fracture healing was determined by mechanical testing and histologic evaluation. The bending strength of each fractured femur was expressed as a percentage of the strength of the intact, contralateral femur. Histologic evaluation was performed on serial longitudinal sections stained with hematoxylin and eosin using a qualitative score of maturity of the callus. Ibuprofen and indomethacin both retarded fracture healing, with significant differences in "mechanical healing" found between the control and experimental groups after 10 weeks of drug administration. Both drugs also induced qualitative histologic changes manifested by delayed maturation of callus, which was noticeable earlier than the difference found by mechanical testing of bone. Our data suggest that NSAIDs have an inhibitory effect on fracture repair that is reversible after cessation of indomethacin but not ibuprofen.

Fracture healing and mast cells.

We analyzed the morphology and localization of mast cells during the course of fracture repair in control rats and in animals with delayed healing of fractures induced by nonsteroidal antiinflammatory drugs (NSAIDs). In the first 2 weeks of fracture healing in control animals, mast cells were found either in the vicinity of blood vessels or in the vascularized tissue proliferating into the cartilaginous portion of subperiosteal callus. In the later stages (6-8 weeks), mast cells were seen in loose connective tissue in bone marrow surrounded with translucent ground substance. At this stage of healing, a hyperplasia of mast cells and cell degranulation was often seen in close proximity to osteoclasts and areas of bone resorption. Treatment with NSAIDs delayed fracture healing and the appearance of mast cell hyperplasia in bone marrow for approximately 4 weeks, suggesting that mast cells have specifically defined temporal and regional distribution during the process of bone repair. Histochemical studies documented a significant amount of chymase in the mast cells in callus. This enzyme was purified from mast cells by chromatography and was able to digest in vitro proteins extracted from bone. Our data suggest that mast cells in fracture healing are involved in digestion of extracellular matrix in callus tissue that could facilitate (a) angiogenesis in the early stages of healing, and (b) the replacement of provisional tissue with newly formed bone in the later stages of fracture healing.

The effect of etidronate on late development of heterotopic ossification after spinal cord injury.

Forty patients with spinal cord injury (SCI) and heterotopic ossification (HO) were treated with etidronate and followed after therapy to determine the effects of long-term medication on heterotopic bone formation. Eighteen patients had tetraplegia and 22 had paraplegia. Early diagnosis of HO (positive bone scintigraphy and negative radiographic findings of HO) was established by 3-phase bone scintigraphy using 99m technetium-labeled methylene diphosphonate. All patients underwent treatment with etidronate, first with intravenous administration of 300 mg/day for 3 days followed by an oral administration of 20 mg/kg/day for 6 months. Eleven patients (27.5%) developed radiographic evidence of HO from 1.5 to 6 years after therapy. A low degree of HO was found in these patients; 8 had grade I and 3 had grade II ectopic ossification (Brooker's scale). The analysis of data showed that 2 different types of ectopic bone may form in the later stages after SCI. In 5% of patients, HO was found in the same anatomical site initially and finally, suggesting a "rebound" in mineralization of bone matrix not prevented by the administration of etidronate. The other type of HO was found in the majority of patients (95%) where the localization of HO showed different involvement of joints than initially, indicating de novo appearance of HO following SCI. The data suggest that etidronate given for a prolonged period in higher doses has, in addition to an inhibitory effect on crystal formation, a cellular effect on bone-forming cells.

Treatment of heterotopic ossification after spinal cord injury.

A new protocol in management of heterotopic ossification (HO) was evaluated in 46 patients after spinal cord injury (SCI). A group of 24 paraplegic and 22 tetraplegic patients was involved in a prospective study. Diagnosis of HO was made by bone scintigraphy and radiographic evaluation. Patients were divided into two groups. Group I was made up of 33 patients with positive bone scintigraphy and negative evidence of HO and Group II was made up of 13 patients with positive bone scintigraphy and positive radiographic evidence of HO. Etidronate was started intravenously (300 mg/day) for three days followed by oral therapy for six months (20 mg/kg/day). Follow-up of patients was 15.7 +/- 8 months after SCI. In Group I, etidronate therapy prevented the development of HO in 79 percent of patients; in 21 percent of patients, a low degree of tissue ossification was found which was not clinically significant. In Group II, there was an inhibitory effect of etidronate on progression of soft tissue ossification in six patients. The remaining seven patients did not respond to therapy and showed an increased growth of HO. Our data indicate that etidronate may prevent HO in the majority of patients when administered at an early stage of HO development and in higher doses than are routinely recommended.

Determination of replacement and suppressive doses of thyroxine.

Suppression daily doses of thyroxine (T4) were determined and the daily amounts of T4 required to replace T4 were established in 217 hypothyroid patients. Patients with Hashimoto's thyroiditis treated daily with 2-3 micrograms/kg lean body mass or 1-2 micrograms/kg body weight T4 had normal serum thyrotrophin (TSH) concentrations, normal response to TSH-releasing hormone (TRH) and normal systolic time intervals but doses higher than 3 micrograms/kg lean body mass or 2 micrograms/kg body weight decreased serum TSH concentrations, with no response to TRH and systolic time intervals typical of hyperthyroidism. In 13/32 (41%) hypothyroid patients with Graves' disease following 131I and/or surgery, the daily T4 replacement dose was similar to that in Hashimoto's thyroiditis patients but in 12 (38%) patients daily doses of 2-3 micrograms/kg lean body mass or 1-2 micrograms/kg body weight T4 increased serum T4 and suppressed TSH levels, and in six (9%) lower doses were required to control hypothyroidism. The T4 suppression dose for patients with thyroid cancer was more than 3 micrograms/kg lean body mass or 2 micrograms/kg body weight, whereas approximately 30% of non-toxic nodular goitre patients required less than 3 micrograms/kg lean body mass. It is concluded that replacement or suppression doses of T4 should be individually determined and that different criteria should be applied for their calculation depending on the thyroid abnormality.

Relative increase of serum reverse T3 in patients with hypothyroidism.

In 17 hypothyroid patients serum T3: rT3 ratio was 7.5 /+- 1.1 which was significantly lower than in control subjects (12.2 /+- 0.6; p less than 0.001). The data suggest that in hypothyroidism the organism might shift conversion of T4 from biologically active T3 to biologically inactive rT3 which may not be a defense mechanism of the body, as it was found in chronic systemic illness.

Competitive ligand - binding assay for thyroxine binding globulin. Comparison with TBG radioimmunoassay and T3 uptake test.

A simple and reproducible competitive ligand binding assay has been utilized to measure serum TBG concentration. In euthyroid subjects TBG concentration (mean +/- SD, mg/l) was 33.7 +/- 4; hyperthyroid 24 -/+ 6; T3-thyrotoxicosis 20 +/- 7; hypothyroid 37 -/+ 7; pregnant 67 -/+ 18; post-partum period 59.8 -/+ 17; oral contraceptives 45 -/+ 7. The correlation of CLBA with RIA measurement of TBG was significant (p less than 0.001). The estimations of serum TBG by CLBA correlated significantly with T3 uptake test (p less than 0.001), but at higher concentration of TBG correlation was non-linear. T4 : TBG ration according to serum T4 and TBG concentration provided a reliable index in the assessment of thyroid function.

A study comparing sterile and nonsterile urethral catheterization in patients with spinal cord injury.

This study was designed to determine the effect of sterile and nonsterile intermittent catheterization on the incidence of urinary tract infection (UTI) in patients after spinal cord injury. The study included 29 patients with neurogenic bladder dysfunction treated with intermittent catheterization. One group of 14 patients was on sterile catheterization; another group of 15 patients was on nonsterile catheterization. On a weekly basis, urine samples were obtained and analyzed. A total of 122 urine samples were analyzed. The patients on sterile catheterization had a 28.6% UTI incidence; the group using a nonsterile catheterization technique had a UTI incidence of 42.4%. The most common urinary pathogen in both groups was E. coli (65%). The cost of antibiotics for patients on the sterile catheterization program was only 43% of the cost of antibiotics for those on the nonsterile program. However, the sterile kits cost 371% of the cost of the catheterization kits for the patients in the nonsterile program, so the total cost of managing neurogenic bladder on the sterile program was 277% of the cost of the nonsterile program.