Incidence of hypothyroidism after radioactive iodine therapy for thyrotoxicosis in Hong Kong Chinese

The incidence of hypothyroidism in 1396 Chinese patients in Hong Kong treated for hyperthyroidism with 131I therapy is presented using the life-table method of analysis. One year after therapy only 6% of patients were hypothyroid, but the subsequent annual incidence was 3.5%, emphasising the need for life-time surveillance of these patients. A higher incidence of subsequent hypothyroidism was found in patients with diffuse surgical treatment, the total dose or number of doses of 131I, the severity of thyrotoxicosis and the age of the patient did not influence the rate of onset of hypothyroidism. The data suggest that in order to minimise the occurrence of hypothyroidism a lower dose of 131I per gram of thyroid mass should be used for patients with small diffuse glands.

Deep vein thrombosis and changes in coagulation and fibrinolysis after gynaecological operations in Chinese: the effect of oral contraceptives and malignant disease

Of 154 Chinese patients who underwent gynaecological operations, four showed a positive 125I fibrinogen leg scan for venous thrombosis, and overall incidence of 2 . 6%. In those who were on oral contraceptives and had major pelvic surgery for benign conditions, the incidence was 10 . 5%; in those who had Wertheim hysterectomy for carcinoma of cervix, it was 6 . 7%. This confirms the rarity of post-operative thromboembolism in the Chinese. Fragment E showed a biphasic rise after major operation due to tissue injury and venous thrombosis. In patients with malignancy, the postoperative 'fibrinolytic shutdown', represented by decreased plasminogen activator together with increased alpha 1 antitrypsin and C1- inhibitor levels, was more marked. In addition, alpha 2 macroglobulin level was lower and fell significantly after operation. In patients on oral contraceptives, fragment E levels were higher after surgery and there was no decrease in plasminogen activator levels. Antithrombin III levels did not fall except in three of the four patients with venous thrombosis. A marked increase in fragment E level and a decrease in antithrombin III level might be useful diagnostic markers for postoperative venous thrombosis.

Globin chain synthesis in haemoglobin New York (beta 113 replaced by glutamic acid)

The presence of Hb New York was confirmed in a Chinese family in which affected members have occasional red cells with Hb-H-like inclusions and a relative decrease in alpha chain synthesis, suggestive of a coexisting alpha thalassaemia trait. However, globin gene mapping and DNA hybridization revealed no deletion of the alpha genome. Timed-incubation experiments showed that the rate of synthesis of beta NY chain was greater than that of normal beta chain in the early periods. Chromatographic separation of Hb NY and Hb A before chain analysis revealed preferential binding of newly synthesized alpha chains to beta NY, with a four-fold increase in specific activity of the alpha Hb NY chains. It is concluded that beta NY chain is being synthesized more rapidly and its increased turnover may account for this presentation of apparent alpha chain deficiency.

Two different molecular organizations account for the single alpha-globin gene of the alpha-thalassemia-2 genotype

The alpha-thalassemia-2 (alpha-thal-2) genotype or mild alpha-thalassemia gene consists of a single structural alpha-globin gene on the chromosome that normally bears two alpha-globin genes. We used blot hybridization to investigate variation in the molecular organization of this genotype and to determine the distributions of these variations in the world population. Two different patterns of gene organization responsible for the alpha-thal-2 genotype were found: the first was the result of a 4.2-kilobase pair deletion involving the normal 5' alpha-globin gene (leftward deletion alpha-thal-2 genotype), and the second probably the result of a crossover deletion of a DNA fragment bridging the two normal alpha-globin genes (rightward deletion alpha-thal-2- genotype). The rightward deletion was found in all 9 Black subjects, all 8 Mediterranean subjects, and 4 of 13 Chinese subjects. The leftward deletion was found in four and the nondeletion alpha-thalassemia lesion was found in five of the nine remaining Chinese subjects. It is likely that these deletions are related to specific DNA sequences that determine DNA recombinational events.

Direct inhibition of testicular function by gonadotropin-releasing hormone: mediation by specific gonadotropin-releasing hormone receptors in interstitial cells

Agonist analogs of gonadotropin-releasing hormone (GnRH) have been shown to exert antigonadal effects in male and female animals. In hypophysectomized male rats treated with follicle-stimulating hormone, administration of a potent GnRH agonist caused depletion of luteinizing hormone and prolactin receptors and marked suppression of serum testosterone levels. The possibility that such direct effects of GnRH agonists on testicular function could be expressed through specific receptors located in the interstitial cells of the testis was supported by the selective concentration of a 125I-labeled GnRH agonist by the testis in vivo. Specific receptors for the releasing hormone were demonstrated in testis particles and dispersed interstitial cells by direct binding analysis with the 125I-labeled GnRH agonist. The binding affinity (Ka = G X 10(9) M-1) and peptide specificity of the testicular GnRH binding sites were similar to those of anterior pituitary and ovarian GnRH receptors. The presence of GnRH receptors in the testis indicates that these sites mediate the direct inhibitory actions of GnRH agonists upon testicular endocrine function.

Lactogenic receptor regulation in hormone-stimulated steroidogenic cells

Receptor sites for lactogenic hormones such as prolactin (PRL), human growth hormone (HGH), and placental lactogens, are widely distributed in mammalian tissues, including mammary glands, steroid-secreting cells of the adrenal, testis, and ovary, and target cells of steroid hormone action such as liver, prostrate, and kidney. Although the biological functions of lactogen binding sites remain uncertain, a relationship between prolactin and lipoprotein metabolism is implied by the occurrence of prolactin receptors in steroidogenic cells of the gonads and adrenal, and by the ability of prolactin to increase esterified cholesterol in the testis. Recently, loss of testicular prolactin receptors has been observed following elevation of circulating luteinising hormone (LH) concentrations by the gonadotropin releasing hormone (GnRH) and its agonist analogues. The hormone dependence of lactogen receptor sites in steroid-secreting cells was further analysed in rat testis, ovary, and adrenal glands after treatment with the respective trophic hormones, gonadotropin and ACTH. In each of these tissues, rapid and transient loss of lactogen receptors was observed after trophic hormone stimulation. These findings indicate that increased turnover of lactogen receptors is an important component of the target-cell response, and suggest that prolactin receptors might be involved in the transport of lipoprotein precursors for steroid biosynthesis.

Dissociated thyroxine, triiodothyronine and reverse triiodothyronine levels in patients with familial goitre due to iodide organification defects

The thyroid function of patients with three different types of organification defect was studied. All patients were characterized by a high thyroidal 131I uptake and a positive perchlorate discharge. Patients with Pendred's syndrome who had goitre and congenital nerve deafness were mostly euthyroid with normal circulating thyroid hormone levels. Only two of them had compensated euthyroidism with elevated total T3, high basal TSH and delayed return to basal value with TRH. The patients who were euthyroid with large goitres and normal hearing had elevated total T3 and an exaggerated TSH response to TRH. The thyroid function of these two groups of patients contrasted with that of goitrous cretins, who were clinically hypothyroid with low circulating total T4, increased T3 and decreased rT3 levels. The data suggest that in patients with intrathyroidal iodine deficiency secondary to organification defect, there is preferential T3 production in an effort to maintain euthyroid state, and this is further substantiated in the case of gross thyroid insufficiency either by enhanced peripheral conversion of T4 to T3, or reduced metabolic clearance of T3 and increased clearance of rT3, resulting in elevated T3 and decreased rT3 levels.

Treatment of acromegaly with bromocriptine

Five men and three women with active acromegaly were treated with bromocriptine. After three months' therapy (30 mg/day) mean GH during the day decreased by 50% in six out of eight subjects. In the remaining two subjects (non-responders) GH was persistently over 100 micrograms/l. Mean GH during glucose tolerance test were not significantly decreased in three out of the eight subjects, of whom two were the nonresponders. The minimum dose of bromocriptine required to achieve maximum GH suppression ranged from 7.5 to 20 mg/day. In contrast, serum prolactin (PRL) throughout the day suppressed significantly in all subjects after 5 mg/day bromocriptine. Decreases in clinical symptoms, hand volume, urinary hydroxyproline and calcium excretion were seen in about half of the subjects. Three of the four subjects with diabetes mellitus showed improvement in glucose tolerance. Although minor side effects were uncommon, one patient died because of massive gastrointestinal haemorrhage from a duodenal ulcer.

Effects of heroin addiction on thyrotrophin, thyroid hormones and porlactin secretion in men

Pituitary-thyroid function in male heroin addicts and addicts after abstinence (ex-addicts) was studied and compared with that of healthy euthyroid men. In heroin addicts the increases in circulating total thyroxine and triiodothyronine levels were accompanied by an increase in the thyroid hormone uptake test. These changes may reflect a quantitative increase in thyroxine binding globulin. Reverse triiodothyronine concentrations in heroin addicts were normal. The thyrotrophin-releasing hormone elicited a diminished thyrotrophin response in heroin addicts which was significantly different from that in control subjects and ex-addicts. An elevation of serum prolactin was noted in heroin addicts, while ex-addicts had normal levels. Gradual recovery of pituitary-thyroid function occurred after heroin withdrawal.

The determination of antithrombin III by radioimmunoassay and its clinical application

A radioimmunoassay (RIA) had been developed for the determination of antithrombin III (AT III) in man. The detection limit was 25 microgram/dl. AT III-RIA level and biological activity (anti-Xa) was significantly correlated (r = 0.737, P less than 0.001). Plasma levels in 36 healthy males (mean +/- SD, 19.9 +/- 2.5 mg/dl) and 21 healthy females (19.1 +/- 2.4 mg/dl) were similar. Serial AT III measurements in normal menstruating females showed lower levels during midcycle and higher concentrations during menstruation. In carcinomas, the AT III levels were lower than normal, particularly in hepatocellular carcinoma. In cirrhosis of liver, the levels were markedly decreased and in some patients were below that found in congenital AT III deficiency. Patients with deep vein thrombosis and patients with heart valve replacement had lower levels than normal, while patients with cerebral vascular occlusion had normal levels. The possible use of AT III as a diagnostic tool of post-operative deep vein thrombosis was demonstrated in one patient after hysterectomy. The increased sensitivity, specificity and precision of this type of assay offer distinct advantages over existing methods of AT III estimation.

Heparin-antithrombin III binding. In vitro and in vivo studies

Heparin antithrombin III binding was studied by crossed immunoelectrophoresis. In plasma and purified antithrombin III standard, multicomponent patterns were obtained with low concentrations of mucosal heparin. There is evidence that antithrombin III may bind more than one heparin molecule. At high heparin concentration (greater than 16 U/ml), single symmetrical peaks were obtained. Serum samples showed two antithrombin III peaks due to a decreased heparin binding of the slower peak (2.1-3.9 times), which was probably antithrombin III-activated procoagulant complexes. Heparin analogue (A 73025) also bound antithrombin III in vitro but the mobility of the peak was slower than with mucosal heparin and only a single peak was obtained in serum samples. Radioimmunoassay showed a decreased binding of antithrombin III antibody to heparin-antithrombin III complex. Venous occlusion to the forearm resulted in a slow second peak in the plasma. Heparin therapy gave rise to a double peak in the plasma antithrombin III profile and with continuous infusion, quantitative decreases were noted in all subjects studied, two of whom rethrombosed at the end of 7 days therapy.

The effect of heroin addiction on pituitary-testicular function

The effect of heroin addiction on pituitary-testicular function was studied in 54 active and 19 abstinent addicts and their results were compared with those of 43 age-matched controls. Abnormal sexual function was frequently found in heroin addicts and this persisted after drug withdrawal. The mean total (mean +/- SE, 18.1 +/- 1.0 nmol/1) and free (0.17 +/- 0.03 nmol/1) testosterone (T) levels in heroin addicts were significantly lower than those in healthy controls (total T 22.8 +/- 1.1 nmol/1), P less than 0.005; free T 0.30 +/- 0.03 nmol/1, P less than 0.005). The mean sex hormone binding globulin binding capacity was higher in heroin addicts (60.1 +/- 5.2 mM) than in healthy controls (35.5 +/- 2.1 mM). These hormonal changes returned promptly to normal after withdrawal. The basal LH and FSH and the responses to LHRH were comparable in the three groups studied. The finding of significantly lower total and free T together with higher SHBG indicates an abnormal testicular function in heroin addiction. Normal basal and LHRH-stimulated LH and FSH levels suggest that chronic heroin abuse depressed testicular function via the hypothalamus or higher centres.

The relationship between circadian variations in circulating thyrotrophin, thyroid hormones and prolactin

Half-hourly blood samples were taken from six clinically euthyroid men over a continuous period of 24 h. Their concentrations of total thyroxine (T4), total triiodothyronine (T3), thyrotrophin (TSH) and prolactin (PRL) were assessed together with the degree of unsaturation of thyroid hormone binding proteins as determined by the thyroid hormone uptake test (THUT). Both T3 and T4 were also measured in urine samples collected serially during the same 24 h period. Significant circadian changes in serum TSH, THUT, serum and urine T4 and serum PRL were demonstrated in all subjects. TSH showed a reciprocal pattern to serum T4, with higher levels during the evening and at night than the daytime. This TSH pattern did not coincide with PRL secretion. Further studies on the same subjects did not show any significant effect of posture, corticosteroid or T4 administration upon circadian changes in TSH. There appeared to be no consistent circadian changes in serum or urinary T3. It seems likely that the TSH circadian rhythm is centrally determined and that free T3 levels are maintained more or less constant by variation in peripheral conversion from T4.

Effect of acute myocardial infarction on pituitary-testicular function

The effect of acute myocardial infarction on the secretions of LH, FSH and testosterone was studied in thirteen male patients. Plasma testosterone fell transiently on the fourth day after acute myocardial infarction. This was accompanied by a rise in LH on the same day which persisted for a week after infarction. Serum FSH showed no significant change. The data suggest that following the medical stress of myocardial infarction, testosterone concentration was suppressed resulting in a compensatory rise in LH.

Effect of surgical stress on pituitary-testicular function

The effect of surgical stress on the secretions of LH, FSH, testosterone (T) and oestradiol (E2) were studied in twelve male patients. During surgery LH rose significantly; post-operatively, LH fell but remained persistently elevated a week after operation. However, T and E2 fell progressively to a nadir on the second and fifth post-operative day respectively and remained suppressed. Serum FSH showed no significant change. Despite a post-operative decrease in sex hormone binding globulin (SHBG) binding capacity, non-SHBG bound T showed a decrease parallel to T. Multiple sampling studies showed that the secretions of LH were increased and that of T were decreased post-operatively. Following surgery, LH responses to LHRH were magnified, FSH and T responses showed no significant change when compared with the pre-operative responses. These data suggest that secretions of LH were increased during surgery. Following surgical stress, T and E2 concentrations were suppressed resulting in a compensatory elevation of LH concentrations.

Transfer of digoxin across the placenta and into breast milk

Eleven mothers given digoxin throughout pregnancy because of rheumatic heart disease were studied. Digoxin was identified in the placenta and, for the first time, in milk. Paired cord and maternal blood samples obtained at parturition showed lower digoxin levels in cord blood than in maternal blood. The total tissue-bound digoxin level in the placenta correlated closely with maternal digoxin levels. These findings suggest strongly the presence of a placental barrier for digoxin. Similar digoxin concentrations (0.825 +/- 0.015 nmol/l) were found in milk samples obtained daily between the third and seventh days post partum. The half-life of digoxin in the newborn was 36.2 +/- 5.43 hours (Mean +/- SEM); thus all the digoxin present at birth would be excreted within 10 to 11 days.

Pituitary-thyroid responses to surgical stress

The effect of surgery on pituitary-thyroid function was studied in 12 euthyroid patients. There was a sharp early increase in total thyroxine level, causing displacement of triiodothyronine from thyroid hormone binding proteins resulting in the elevation of the biologically more potent free triiodothyronine fraction. The serum triiodothyronine concentration fell rapidly during and after the operation, with a concomitant rise in reverse triiodothyronine level. Increased prolactin levels were found during and after surgery. With no post-operative complication, recovery of normal pituitary-thyroid function occurred after 4 to 7 days of convalescence.

Thyrotoxicosis: relations between clinical state and biochemical changes during carbimazole treatment

The relation between clinical and biochemical changes in thyrotoxicosis were studied in 12 patients with Graves's disease who were being treated with carbimazole. Clinical assessment (using the Crooks-Wayne index) was combined with the measurement of free thyroxine and triiodothyronine indices (FT4I and FT3I) and the assessment of two tissue markers of thyroid hormone action--sex-hormone-binding globulin (SHBG) levels and the thyrotrophin responses to TRH. In general the FT4I and FT3I fell rapidly once treatment was started, and returned to normal in one to four weeks, followed shortly by SHBG levels. The thyrotrophin response returned at this time in two patients, who still had borderline high levels of FT3I and SHBG. The clinical score fell more slowly and variably and was less closely related to any of the biochemical indices than these were to each other. During the early phase of treatment with antithyroid drug the clinical evaluation may be an unreliable indicator of persisting thyroid hormone excess, and when the patient seems clinically but not biochemically thyrotoxic the symptoms should be treated on their own merits with beta-blocking drugs and not with increased doses of antithyroid drugs.

Stability of thyroxine and triiodothyronine in biological fluids

The stability of thyroxine and triiodothyronine in serum has been investigated. Apparent levels of total thryroxine, as determined by two different protein-binding assays employing thyroxine-binding globulin as the binding protein, increased significantly in serum and plasma samples stored at room temperature and were signficantly lower in haemolysed samples. Values did not change significantly in samples stored at 4 degrees C, nor in samples stored at room temperature when determined by radioimmunoassay. Total triiodothyronine levels, as determined by radioimmunoassay, fell slightly on storage. Failure to appreciate the effect of storing samples at room temperature on apparent levels of total thyroxine, as determined by some protein-binding assays, could lead to an incorrect assessment of thyroid status.

Assessment of thyroid function during pregnancy

Serum levels of thyroid stimulating hormone and of the two thyroid hormones were compared in pregnant women and in non-pregnant control subjects. Circulating levels of thyroid stimulating hormone did not alter significantly throughout pregnancy. Total thyroxine and triiodothyronine concentrations increased markedly during the first and second trimesters, associated with a progressive increase in the thyroid binding capacity of serum proteins. Urinary triiodothyronine and thyroxine excretion during the third trimester of pregnancy was comparable to that found in non-pregnant euthyroid females and, it is concluded, provides the simplest method of assessing thyroid function during pregnancy.

The assay of urinary thyroid hormones for assessing thyroid function

A competitive protein binding assay for thyroxine (T-4) and a radioimmunoassay for tri-iodothyronine (T-3) were applied to determine the urinary concentrations of these hormones. These measurements were shown to offer excellent diagnostic discrimination between euthyroid, hypothyroid, and hyperthyroid subjects. Urinary T-3 and T-4 levels were not affected by changes in the concentration of thyroxine binding globulin (TBG) or by changes in binding capacity; and therefore, remained normal during pregnancy, oestrogen, and phenytoin therapy. There was no significant circadian variation in urine T-3 excretion. Thus T-3 assays of overnight urine samples could be used in conjunction with dynamic test procedures, such as thyrotrophin (TSH) stimulation test, to enable the rapid assessment of the integrity of the hypothalamic-pituitary-thyroid axis.

Effects of oestrogen on urinary thyrosine excretion

The day to day variation and the effects of oestrogen on the urinary excretion of thyroxine (T-4) were studied in euthyroid women and men. Serial urinary T-4 values over a period of 28 consecutive days were found to lie within relatively narrow limits except for a transient increase during menstruation in women. During oestrogen therapy urinary T-4 was unchanged, but an appreciable rise was seen after stopping oral ovulation inhibitors in women. A similar effect was seen in men after three days' treatment with 20 mug/day of ethinyloestradiol. The increased urinary T-4 excretion on oestrogen withdrawal reached a maximum in one to three days. This response contrasted with that produced by phenytoin, a drug known to bind to thyroxine binding globulin, and which resulted in increased urinary T-4 excretion during the period that it was being administered.

Comparison of two triiodothyronine uptake techniques for the assessment of thyroid function

The present study was designed to compare the Thyopac and Triosorb triiodothyronine uptake tests. A normal range was established for the two procedures. Neither test was affected by iodine-containing drugs or contrast media but abnormal results were obtained during pregnancy and in subjects receiving oestrogens. Both tests proved satisfactory in the diagnosis of hypo- and hyperthyroidism, giving results consistent with clinical assessment and with serum protein-bound iodine determinations. The Thyopac procedure was preferred for a number of reasons. It requires less plasma; it is slightly simpler and quicker and it is not time dependent.