Acute changes in thyroid volume and function following 131I therapy of multinodular goitre

OBJECTIVE

Many textbooks claim that radioiodine (131I) treatment should be given with care to a goitre with substernal extension, for fear of acute swelling of the gland and thus respiratory problems. Since 131I is used increasingly in the treatment of non-toxic as well as toxic goitre we have evaluated the acute changes in thyroid volume following 131I therapy.

DESIGN

Evaluation of potential acute changes in thyroid volume and function after 131I treatment in patients with non-toxic goitre treated because of compression symptoms or for cosmetic reasons, as well as in patients with toxic goitre.

PATIENTS

Out-patients with multinodular goitre, either non-toxic (n = 20) or toxic (n = 10). Excluded were patients with a substernal goitre.

MEASUREMENTS

Ultrasonically determined thyroid volume and standard thyroid function variables were investigated before and 2, 7, 14, 21, 28 and 35 days after treatment.

RESULTS

In non-toxic goitres the thyroid volume did not increase significantly, the maximum increase in the median volume being 4% on day 7. Serum levels of free T3 and free T4 indices increased by 20% (day 7) and 13% (day 14) (P = 0.002), respectively. Likewise thyroid volume in toxic nodular goitre did not change significantly after 131I treatment (maximum median increase was 2%). None of the patients presented symptoms of tracheal compression.

CONCLUSIONS

131I treatment of non-toxic as well as toxic multinodular goitre does not seem to increase thyroid volume.

Changes in bone mass during prolonged subclinical hyperthyroidism due to L-thyroxine treatment: a meta-analysis

L-Thyroxine (L-T4) in the treatment of thyroid disease resulting in reduced serum thyrotropin (TSH) has been associated with reduced bone mass and thus the potential risk of premature development of osteoporosis. However, several recent studies have failed to show such a detrimental effect. These disagreements are probably due to only a small number of patients taking part in each study, decreasing the change of finding significant differences and increasing the risk of missing a real difference (type 1 and 2 errors, respectively). We therefore performed a meta-analysis on the available papers (N = 13), in which bone mass was measured in the distal forearm, femoral neck or lumbar spine in a cross-sectional manner in women with suppressed serum TSH due to L-T4 treatment and in a control group. The women were divided according to their pre- and postmenopausal state, because preserved estrogen production plays a protective role against irreversible bone loss. Based on the number of measurements performed on the different sites of the skeleton, a theoretical bone composed of 30.4% distal forearm, 28.8% femoral neck and 40.8% lumbar spine could be constructed in premenopausal women (441 measurements). A premenopausal woman at an average age of 39.6 years and treated with 164 micrograms L-T4/day for 8.5 years, leading to suppressed serum TSH, had 2.67% less bone mass than controls (NS), corresponding to an excess annual bone loss of 0.31% after 8.5 years of treatment (NS). The risk of not detecting an excess bone loss of at least 1% per year (type 2 error) was p < 0.15.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone metabolism in premenopausal women with nontoxic goiter and reduced serum thyrotropin levels

OBJECTIVE

To study whether premenopausal women with nontoxic goiter, but reduced serum TSH as a sign of spontaneous subclinical hyperthyroidism have decreased bone mass or other indications of increased bone turnover.

DESIGN AND SUBJECTS

In a cross-sectional study, bone mass measurements were performed in the distal forearm and the lumbar spine in 11 premenopausal women with nontoxic goiter and a stable reduction in serum TSH (median (range) 8 months (6-108 months)), and in 22 matched controls. In a longitudinal study, measurements were repeated every 3 months for a maximum period of 2 years in 9 of the patients (6 completed 9 months, 4 completed 2 years follow-up).

RESULTS

Serum TSH in the patients were (median (range)) 0.025 mU/l (< 0.005-0.256 mU/l). Patients had a bone mineral content of the distal forearm and a bone mineral density of the lumbar spine similar to those of controls, medians of controls: 98.4% and 93.8%, respectively. The risk of a type 2 error for over-looking a 10% difference was 2% for the distal forearm and 20% for the spine. TSH correlated negatively with marginal significance (p < 0.10) with markers of bone turnover: plasma osteocalcin, serum alkaline phosphatase, and fasting urinary hydroxyproline corrected for creatinine, although all patients had absolute values of these parameters within normal range. During follow-up bone mass measurements did not tend to decrease, but serum alkaline phosphatase and fasting urinary hydroxyproline showed increasing trends (p < 0.05).

CONCLUSIONS

Premenopausal women with nontoxic goiter and reduced serum TSH do not seem to have reduced bone mass but seem to demonstrate signs of increased bone turnover.

Scintigraphic evaluation of esophageal transit and gastric emptying in familial dysautonomia

Gastroesophageal dysfunction is a major cause of morbidity and mortality in patients with familial dysautonomia (FD). Most studies evaluating esophageal and gastric function in FD patients are either insensitive or invasive. Thus we have used a "milk" scan to quantitate abnormalities in esophageal transit and gastric emptying, while searching for gastroesophageal reflux and aspiration in these patients. The quantitative scintigraphic evaluation was performed in 35 patients with FD, 10 of whom were studied after fundoplication, pyloroplasty and gastrostomy. A prolonged esophageal transit time, ranging from 8 s to more than 60 s duration, was demonstrated in 11 patients. Gastroesophageal reflux was detected in 26 patients. In 16 patients delayed gastric emptying ranging from 63-94% was detected at 30 min, and in 13 patients delayed emptying ranging from 37-86% was observed at 120 min. Pulmonary aspiration was detected in 8 non-operated patients, four of whom had abnormal gastric emptying. The scintigraphic analysis of both esophageal transit and gastric emptying in familial dysautonomia is presented, and its role in evaluation and management of these patients discussed.

Free thyroxine measured in undiluted serum by dialysis and ultrafiltration: effects of non-thyroidal illness, and an acute load of salicylate or heparin

In vitro dilution of serum during processing of a free T4 assay explains to some extent the divergent results obtained in non-thyroidal illness. If serum from such patients contains low affinity T4 protein binding inhibitors, as has been suggested, in vitro dilution will result in spuriously reduced serum free T4 measurements. If these inhibitors cross the dialysis membrane in an equilibrium dialysis assay, their inhibitory effect will be weakened, and in vitro free T4 levels will decrease, even in undiluted serum. In contrast, ultrafiltration methods on undiluted serum seem accurate. We have compared a new, commercially available dialysis technique with an in-house ultrafiltration method for free T4 measurements in undiluted serum. Control subjects (n = 41) had 14% higher free T4 (P < 0.02) by ultrafiltration. Non-thyroidally ill patients not receiving glucocorticoids or dopamine (n = 54) had unaltered free T4 levels, 28.4 +/- 10.3 pmol/l (dialysis) and 31.0 +/- 10.3 pmol/l (ultrafiltration). Dopamine infusion in somatic ill patients (n = 11) resulted in reduced free T4 in both assays but only significantly for dialysis, and subjects with familial dysalbuminemic hyperthyroxinemia (n = 8) had unaltered free T4 levels in both assays. Salicylate (1.5 g) given orally 09:00 h. (n = 5) resulted within 30 min, in increased (P < 0.01) free T4 as measured by both techniques, although more pronounced and sustained as measured by ultrafiltration. Serum TSH decreased concomitantly (P < 0.01). These findings were confirmed when salicylate was administered at 13:00 h. (n = 8). The dialysis procedure resulted in a decrease in serum salicylate of 14% (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Nuclear 3,5,3'-triiodothyronine receptor binding in mononuclear blood cells from patients with malignant blood diseases and small cell carcinoma of the lung

We have previously demonstrated enhanced daily turnover of thyroid hormones in patients with hypermetabolic symptoms due to malignant haematologic disorders or small cell carcinoma of the lung. We hypothesized that some of these symptoms might be due to enhanced peripheral effects of T3. We therefore studied the nuclear T3 receptor binding in circulating mononuclear blood cells in 5 patients with malignant haematologic disorders, 5 with untreated small cell carcinoma of the lung, and 11 healthy controls. Maximal binding capacity of T3 (MBC) was increased 2.5 times in the diseased patients, (median (range)) 110 fmol/mg DNA (75-519) in the haematologic group (p < 0.01), 106 fmol/mg DNA (47-490) (p < 0.10) in small cell carcinoma patients, as compared to 43 fmol/mg DNA (26-94) in controls. The affinity constant Ka of bound T3 was reduced to one-third in the diseased patients. No differences were found between serum thyroid hormone or TSH levels. It is hypothesized, that previously demonstrated enhanced turnover of thyroid hormones in these states of disease might in part be due to increased peripheral consumption of thyroid hormones, including enhanced receptor binding of T3.

Calcitonin gene-related peptide in small cell lung carcinomas

OBJECTIVE

Calcitonin gene-related peptide (CGRP) is a regulatory peptide encoded by the calcitonin gene. CGRP is expressed in increased amounts by the cells of medullary thyroid carcinomas and has been demonstrated by immunohistochemistry to occur in neuroendocrine cells and nerve fibres of lung tissue.

MEASUREMENTS

Serum CGRP levels were measured in patients with small cell lung carcinomas before treatment (n = 74) and immediately before the second course of chemotherapy (n = 30). In-situ hybridization and immunohistochemistry were performed on tumour tissue and CGRP was extracted from two tumours and characterized by gel chromatography and high pressure liquid chromatography.

RESULTS

Serum CGRP levels were elevated in small cell lung carcinomas when compared with healthy controls of similar age and sex (median values 55.0 vs 36.6 pmol/l, P < 0.001), and 27% had levels above the upper normal range. Serum CGRP levels decreased following the initial course of chemotherapy (P < 0.05) but remained elevated when compared to the controls (P < 0.001). In-situ hybridization for CGRP mRNA was positive in three of 17 tumours and immunohistochemistry was positive in seven of 31 tumours investigated. CGRP immunoreactivity extracted from two tumours was characterized by gel chromatography and high pressure liquid chromatography. A major part of the immunoreactivity was demonstrated to represent the intact molecule.

CONCLUSIONS

We found that patients with small cell lung carcinomas had elevated concentration of serum calcitonin gene-related peptide but only 27% had values above the upper normal range. Serum CGRP is therefore of limited value as a tumour marker. Intact CGRP can be extracted from tumour tissue, but in-situ hybridization and immunohistochemistry showed positive reactions in only a few of the tumours investigated. The elevated serum CGRP levels are therefore likely to be largely of extratumoral origin.

[Detection of cerebropathy in neurologic and psychiatric diseases]

The authors made a comprehensive examination of 16 patients--epileptics, alcoholics, psychotic subjects and patients after cerebral contusion. The patients were subjected to a neurological, psychiatric, psychological examination as well as to a morphological examination (X-ray, CT, NMR), physiological examination (EEG, polysomnography, evoked potentials), immunological examination and SPECT. The majority of patients had positive CT and SPECT findings suggesting focal brain damage. These results could be explained only in exceptional cases by injury, the majority was of unknown aetiology. With this corresponded focal EEG abnormalities and in particular sleep disorders, sometimes subjective but always detectable by objective methods. There was always a shortage of REM, sometimes also NONREM sleep. Half the patients were subjected to an immunological examination which was always positive and comprised elevated acute stage proteins and proteins associated with the stress reaction. Numerous data in the literature and the authors' experience indicate that the mentioned pathological findings are not incidental and form, independently on the aetiology, an integrated unit for which the term cerebropathy can be used. A primary role is played by the epileptic focus and its quality, i.e. above all the rate of discharge and site and humoroergic systems of the brain stem, in particular their efficiency and mutual balance. The events have a programmed sequence. At the beginning an epileptic focus develops which influences the surrounding area, secondary and tertiary foci are formed and the thalamo-cortical system is affected. Soon this is followed by an apparent influence of the epileptic activity on structures of the brain-stem. The consequence are changes affecting sleep, mood, mental performance, immunity, endosecretion and paroxysms. Subsequently individual symptoms are already prepared but have a different latency of manifestation and the latter depends also on external provoking influences. The thalamo-cortical reaction is characterized by the manifestation of epileptic paroxysms and sets in after a different interindividual incubation following injury. The same applies to the hippocampal reaction manifested by the organic psychosyndrome. Some symptoms such as changes of immunity, sleep or endosecretory function are not necessarily manifested if the influence of the focus on structures of the brain-stem is not sufficiently intense. Conversely if the effect on the brain-stem and limbic structures is greater and the effect on the thalamo-cortical system smaller, psychotiform behaviour develops. Then there are marked changes of phoria, dynamogeny, rate, affectivity, sleep and hormonal secretion and its equilibrium.

Neurohumoral relations in neurological and psychiatric patients

Sixteen patients-epileptics, alcoholics, psychotics and post-contusion cases-were subjected to neurological, psychiatric, psychological, morphological (X-ray, CT, NMR), physiological (EEG, polysomnography, evoked potentials), immunological and SPECT examination. Most had CT and SPECT signs of focal brain damage. The results were but exceptionally due to injury, most were of unknown etiology. This tallied with EEG focal abnormalities, mainly sleep disorders, sometimes subjective ones, but invariably detectable objectively. In each case there was REM, in some also NONREM sleep deficiency. Half of the cases were tested immunologically, each time with positive results: increased levels of acute-phase protein and stress-reaction proteins. As copious literature and our experience show, the above pathological condition, rather than being accidental, constitute regardless of etiology, an integrated entity which could be called "programme cerebropathy". The primary role is played there by the epileptic focus and its properties, in particular, the speed of discharge and localization and brain stem humoroergic systems, i.e., their performance and mutual balance. There is a program sequence of events, first, and epileptic focus acting on the neighborhood, the rise of secondary and tertiary foci, and influence over the thalamocortical system. Soon afterwards, epileptic activity begins to act on brain-stem structures. This results in changes in sleep, mood, psychic output, immunity, endosecretion, and in paroxysms.

[Intraplacental hematoma following chorionic villi biopsy]

One of the most typical complications following chorionic villae sampling (CVS) is vaginal bleeding shortly or some days after the intervention, resulting in abortion in some cases. We report on a case of intraplacental haematoma (pathology: massive subtotal acute haemorrhagic placental infarct), followed by acute placental insufficiency in the 29th week of pregnancy. Therefore, we decided on an emergency caesarean section.

[Pulmonary embolism: which diagnostic approach?]

The recent literature dealing with the diagnosis of pulmonary embolism is reviewed. Clinical signs, electrocardiogram and arterial blood gases analysis are not very helpful whereas a normal level of blood D-dimers makes the diagnosis of pulmonary embolism very unlikely. Lung scanning must be interpreted carefully in parallel with chest radiography. It is most useful if the pattern is either normal or of high probability. All intermediate scans are inconclusive and need a pulmonary arteriogram. Another option in patients with good cardiorespiratory reserve is the use of repeated non-invasive investigations of the lower limbs.

Subtle changes in serum thyrotrophin (TSH) and sex-hormone-binding globulin (SHBG) levels during long-term follow-up after radioactive iodine in multinodular non-toxic goitre

OBJECTIVE

We investigated possible changes in the pituitary-thyroid axis after radioactive iodine (RAI) treatment of multinodular non-toxic goitre.

DESIGN

Consecutive patients with multinodular non-toxic goitre, who remained euthyroid after radioactive iodine (RAI) treatment.

PATIENTS

Twenty-three women with multinodular non-toxic goitre were followed after treatment with RAI.

MEASUREMENTS

Free T4 index (FT4I), FT3I, free T4, SHBG (immunoradiometric assay), and a third-generation TSH assay (chemiluminetric assay) TSH were measured.

RESULTS

Three weeks after RAI treatment TSH had decreased and SHBG increased (P < 0.05). Only 2/18 patients actually had suppressed TSH values, while 12/18 had values in between euthyroid and toxic levels. Trend analysis from 1.5 to 24 months after RAI treatment demonstrated a progressive increase in TSH (P < 0.01) and gradual decrease in SHBG (P < 0.02). No changes in FT4I, FT3I, or free T4 were found.

CONCLUSION

A third-generation TSH assay gave detailed information about changes in thyroid status when TSH was below normal values. FT4I, FT3I, and free T4 seem to be less sensitive parameters than TSH and SHBG for recording subtle changes in thyroid status after RAI treatment of nodular non-toxic goitre. We demonstrated that changes in the pituitary-thyroid axis continue for a long time after RAI treatment of multinodular non-toxic goitre. These patients should be followed up in order to detect possible late hypothyroidism.

Effect of occupational exposure to cobalt blue dyes on the thyroid volume and function of female plate painters

It has previously been shown that long-term oral exposure to cobalt can cause goiter and myxedema. The effect of industrial cobalt exposure on thyroid volume and function was determined for 61 female plate painters exposed to cobalt blue dyes in two Danish porcelain factories and 48 unexposed referents. Thyroid volume was determined by ultrasonography. The cobalt blue dyes were used in one of two forms, cobalt aluminate (insoluble) and cobalt-zinc silicate (semisoluble). Only the subjects exposed to semisoluble cobalt had a significantly increased urinary cobalt content (1.17 micrograms.mmol-1 versus 0.13 micrograms.mmol-1, P less than 0.0001). These subjects also had increased levels of serum thyroxine (T4) and free thyroxine (FT4I) (P = 0.0001 and 0.0029, respectively), unaltered serum thyroid stimulating hormone (TSH), and marginally reduced 3,5,3'-triiodothyronine (T3), whereas thyroid volume tended to be lower (P = 0.14). The group exposed to insoluble cobalt did not differ significantly in any thyroid-related parameters. No correlation between urinary cobalt and FT4I or thyroid volume was found. The study demonstrates an effect of cobalt on thyroid hormone metabolism.

[Nonstandard therapy of epileptics and psychotics]

The authors present their experience with a number of drugs which are not antiepileptics nor antipsychotic drugs but influence the cholinergic and noradrenergic system and glucose and protein metabolism of neurons. Their efficiency in severe epileptics with psychic changes is about 60%. Standard epileptic treatment, mono- and polytherapy, failed completely in these patients. To the authors' "modulating" and "nootropic" therapy applies the same what applies to stereotactic treatment of epilepsy, i.e. that treatment must be started before the epileptic or psychotic process becomes chronic. Epileptogenesis is divided into the following stages: 1. insulation of the brain and development of a lesion (trauma, asphyxia, infection), 2. A. latency, an epileptic focus develops in the lesion, 2. B. latency, secondary and tertiary epileptic foci develop, in particular in the corpus amygdaloideum, hippocampus and fronto-orbital area and from there frequently also psychic changes arise, 2. C. the focus acts also on the thalamo-cortical reverbation circle and gradually "teaches" it epileptic discharges which sometimes can be followed on the EEG, although this stage is still in the latent period, i.e. clinically inapparent. 2. D. modulating structures of the stem fail, REM, i.e. paradox sleep, diminishes. Because these stages resemble those in the development of some psychoses, the psychogenesis of this epileptogenesis is similar; in schizophrenia the deepest stage of NONREM sleep declines. In this stage of epilepsy the inhibitory protective influence of noradrenergic, serotoninergic and dopaminergic (?) systems disappears. The 3rd stage is manifestation of clinical attacks or psychotic behaviour which may be enhanced by some provocation, e.g. alcohol, sleep deprivation, psychic stress, which influence emotivity and the sleep profile. With regard to these stages (insulation, latency, manifestation) treatment should be provided. In the 1st and 2nd stage "nootropic and modulating" treatment should be administered to a greater extent.

[Consciousness and the electroencephalogram]

In the course of 12 years the authors subjected to clinical EEG and stereo-EEG (SEEG) 72 patients (66 epileptics with the diagnosis of psychomotor epilepsy and grand mal) and six psychotic patients suffering from schizophrenia. With the exception of five epileptics and two psychotic patients all subjects had epileptic foci in the amygdalohippocampal complex (AHK). After coagulation of these foci marked improvement of the fits and the mental state occurred in half the patients. During EEG and SEEG recording the authors used different activation methods (hyperventilation through the nose and mouth, sleep, listening to music) and above all direct electric stimulation (ES) of one of the AHK. Secondary epileptic foci had, as a rule, more spikes and a lower threshold for ES than primary ones which contained more delta and slow theta waves. The ES led as a rule to an emotional response, such as anxiety and fear, more rarely to illusions, depersonalization and oneiroid hallucinations and twice to a hedonic response of non-sexual character. The purpose of ES was to assess the site from where it is possible to start the original aura or typical parox. The authors considered these foci, consistent with data in the literature, as the leading focus and it was subsequently coagulated. The authors investigated the reactivity and vigility by the patient's response to sound (the patient had to press a button) and by an interview with the patient. It was revealed that in isolated discharges of the spikes and waves in the scalp electrodes, i.e. in the neocortex, reactivity is lacking. In isolated discharges in the AHK the reactivity was satisfactory, but as a rule anxiety developed. It is thus possible to divide consciousness into emotional consciousness with its site in the AHK, i.e. in the limbic system, and rational consciousness which is a function of the neocrotical system. Congenital changes of consciousness such as vigility or sleep are described as "states" of consciousness. The rational or emotional aspect of behaviour is described as "type" of consciousness. Under normal conditions the states of consciousness alternate periodically and are sharply defined, the types of consciousness are closely linked and are difficult to separate. Under pathological conditions the "states" of consciousness differ less markedly and the "types" of consciousness are in dissociation. Thus obnubilation, depersonalization, illusions, pathic affects etc. develop, as a rule as part of the epileptiform or psychotiform syndrome.

Serum bone Gla protein (BGP) during treatment of hyperthyroidism and hypothyroidism. A longitudinal study

Serum bone gamma-carboxyglutamic acid-containing (Gla) protein (BGP) was measured before and with initially 2 weeks, later 4-8 weeks intervals for 20-58 weeks during treatment of patients with hyperthyroidism (n = 10) and hypothyroidism (n = 4). Biochemical euthyroidism was obtained in the hyperthyroid patients after a median of 3 weeks (range 1-8 weeks), and in the hypothyroid patients after a median of 17 weeks (range 10-27 weeks). Serum BGP levels closely followed the thyroid state, being high respectively low in the hyperthyroid and hypothyroid state and reaching a stable plateau just at the time biochemical euthyroidism was obtained. These data suggest that osteoblastic activity is enhanced in hyperthyroidism and reduced in hypothyroidism, and that normalization occurs in close conjunction with the normalization of the thyroid state, without any delay, indicating a direct effect on the function of the excisting osteoblasts by the thyroid hormones.

Hazardous exposure of ground-living small mammals to cadmium and lead in contaminated terrestrial ecosystems

The dietary exposure to cadmium and lead of two ground-living species of small mammals, i.e., shrews Sorex araneus (Insectivora) and voles Microtus agrestis (Rodentia), was investigated and related to metal loads in target organs (kidneys and liver). The study was done in two natural areas polluted with cadmium and lead originating from urban and industrial metal sources. The average intake of cadmium by the herbivorous voles varied between 0.1 and 0.4 micrograms/g/day and of lead between 2 and 10 micrograms/g/day. The carnivorous shrews showed a considerably higher metal intake rates, i.e., cadmium 3 to 16 micrograms/g/day and lead 19 to 53 micrograms/g/day, which was largely due to the consumption of contaminated earthworms (Oligochaeta). An average cadmium intake of 15 micrograms/g/day or a lead intake of 20 micrograms/g/day corresponded with critical renal metal loads of 120 micrograms/g for cadmium and 25 micrograms/g for lead, which are indicative of adverse health effects. The renal metal loads in shrews reached the critical level, but they remained far below this level in voles. The results indicate a greater risk of toxic exposure to cadmium and lead in soricine shrews than in microtine rodents.

Free thyroxine and 3,3',5'-triiodothyronine levels in cerebrospinal fluid in patients with endogenous depression

Total and free concentrations of T4 and rT3 in serum and cerebrospinal fluid were estimated by ultrafiltration in 12 patients with unipolar endogenous depression before and after electroconvulsive treatment. Recovery from depression resulted in a decrease in CSF concentrations of free T4 (median) (26.2 to 21.4 pmol/l, p less than 0.02) and free rT3 (14.1 to 12.3 pmol/l, p less than 0.05). Concentrations of free T4 in the cerebrospinal fluid were lower than those in serum (p less than 0.02), the ratio being 0.6. In contrast, levels of free rT3 in the cerebrospinal fluid were considerably higher than those found in serum (p less than 0.01), the ratio being 25. These ratios did not change following recovery from depression. In 9 patients with nonthyroidal somatic illness, concentrations of free T4 and rT3 in the cerebrospinal fluid were similar to those found in patients with endogenous depression, whereas 4 hypothyroid patients and one hyperthyroid patient had considerably lower and higher, respectively, concentrations of both free T4 and rT3. In conclusion, levels of free T4 and free rT3 in the cerebrospinal fluid are increased during depression compared with levels after recovery, probably reflecting an increased supply of T4 from serum and an increased production of rT3 from T4 in the brain. The data also suggest that the transport of iodothyronines between serum and the cerebrospinal fluid is restricted.