Drugs and thyroid function

Endocrine Heart Disease

With the increasing prevalence of obesity and diabetes mellitus in the United States, associated cardiovascular disease is reaching epidemic proportions with staggering economic and societal impact. Numerous studies have demonstrated the poorer prognosis associated with chronic coronary artery disease and acute coronary syndromes in patients with diabetes compared with nondiabetic patients. Although the therapeutic strategy is largely the same for the two populations, proper management of the diabetic patient with cardiovascular disease must account for the associated metabolic disturbances. Thyroid disease is the next most common endocrine disorder that affects proper function of cardiovascular patients; all patients presenting with coronary artery disease or cardiac arrhythmias should undergo screening with a sensitive thyroid-stimulating hormone assay and appropriate treatment when necessary. Though these areas are the most common points of intersection between the cardiologist and endocrinologist, a thorough understanding of the impacts of each endocrine system on cardiac function is essential to recognize disease entities that often present with a cardiovascular manifestation or affect patients with a primary cardiovascular disease.

Nonthyroidal illness syndrome: evaluation of thyroid function in sick patients

Altered thyroid function tests as a consequence of illness have been recognized for many years, yet the cause and clinical implications remains uncertain. The routine testing of thyroid function in hospitalized patients should be discouraged, as the results are less predictive of primary thyroid disease than in ambulatory patients. Clinicians should be aware of the methods used for thyroid function testing, as the effect of illness on thyroid function varies among the different tests. The most commonly used free T4 assays likely are influenced significantly by nonthyroidal illness. Advances in understanding the basic mechanisms of thyroid hormone metabolism and thyroid hormone action have given insights into the changes in thyroid function tests as a consequence of nonthyroidal illness. In the future, thyroid hormone receptor isoform-specific agonists and antagonists may allow for more specific treatment of select patients with nonthyroidal illness syndrome.

Case finding and screening strategies for thyroid dysfunction

BACKGROUND

A case can be made for routine testing for thyroid dysfunction (TD) in women aged over 50 years once every 5 years when they present for medical care (case finding). This recommendation is based on: (i) the prevalence of TD, predominantly hypothyroidism, (ii) the insensitivity of standard clinical assessment in detecting even overt TD, (iii) the sensitivity of a single test, serum thyroid stimulating hormone (TSH), in identifying both over- and under-function, (iv) the probable adverse consequences of failure to recognize even mild TD, (v) the safety and effectiveness of treatment, and (vi) presumed lack of adverse effect from the testing program.

METHODS

A normal serum TSH value has a high negative predictive value in ruling out primary TD; if TSH is abnormal, measurement of serum free thyroxine (T(4)) and further clinical assessment are both required to establish the degree of TD.

RESULTS

Case finding identifies more "subclinical" or mild TD (abnormal TSH, normal T(4) and triiodothyronine (T(3))), than overt disease, but a major benefit of widespread testing is the earlier detection and treatment of unsuspected overt disease. There is now evidence that mild TD has adverse consequences and should not merely be regarded as a prognostic indicator, but there is still no consensus whether there is a causal relationship between mild thyroid failure and dyslipidemia.

CONCLUSIONS

A case can be made for treatment of both mild thyrotoxicosis and hypothyroidism, but the therapeutic decision is generally simpler for hypothyroidism.

The acute effect of calcium carbonate on the intestinal absorption of levothyroxine

To determine the acute effect of calcium, we measured levothyroxine absorption after ingestion of thyroxine (T4) with and without simultaneous ingestion of calcium (as calcium carbonate) in seven volunteers without thyroid disease. Serum total T4, total triiodothyronine (T3), free T4, and thyrotropin (TSH) levels were measured after ingestion of 1,000 microg of levothyroxine on two separate visits at 4-week intervals: (1) levothyroxine alone and (2) levothyroxine together with 2.0 g of calcium as calcium carbonate. The amount of absorbed levothyroxine was calculated as the incremental rise in serum T4 level during the first 6 hours multiplied by the volume of distribution for the hormone. When 1,000 microg of levothyroxine alone was given to subjects, the maximum average total T4 absorption was 837 microg (83.7% of the dose ingested) at 120 minutes. When levothyroxine was coadministered with 2.0 g of calcium (as calcium carbonate), the maximum average T4 absorption decreased to 579 microg (57.9% of the dose ingested) at 240 minutes. The total levothyroxine absorption over 6 hours was significantly greater with thyroxine than that with thyroxine and calcium (p = 0.02). The administration of calcium and levothyroxine in these subjects was associated with a significant reduction in the peak increment in serum total T4 (p = 0.02) and free T4 levels (p = 0.03), as well as a significant reduction in the overall increment in serum total T4 (p = 0.003), free T4 (p = 0.002), and total T3 levels (p = 0.01) over four time points (120 minutes, 240 minutes, 360 minutes, 1,440 minutes). In summary, this pharmacokinetic study in seven volunteers indicates that calcium carbonate acutely reduces T4 absorption.

Free thyroid hormone measurement. A critical appraisal

The main purpose of free T4 and free T3 assays is to distinguish reliably between thyrotoxicosis, hypothyroidism, and the euthyroid state, an objective that cannot be attained with assays of total T4 and T3 because of hereditary and acquired variations in the concentrations of binding proteins. Effective correction for changes in the serum concentration of TBG can be achieved with numerous types of free hormone estimate, but other changes in binding are not well accommodated. Despite remarkable methodologic ingenuity, no current method reflects the free T4 concentration in undiluted serum under in vivo conditions. Equilibrium dialysis, widely considered the reference method for free T4 measurement, is also subject to error, either preanalytic, owing to generation of NEFA in the sample leading to an overestimate of free T4, or analytic with underestimation of the effect of competitors to increase free T4. Current approaches to free T4 measurement are vulnerable to several method-dependent artifacts: abnormal albumin binding of T4 or of the assay tracer, the inhibition of T4 binding to TBG by medications, and the effects of critical illness, especially in heparin-treated patients, pregnancy, and the abnormalities in sick premature infants. Because of systematic variation between methods (i.e., whether a technique is albumin dependent or prone to incubation or dilution artifacts), it is essential to consider methodologic details in evaluating free T4 estimates in these situations and whenever estimates of free T4 are clinically discordant. False-positive abnormalities are more frequent than false-negative results. When free T4 results are correlated with the serum TSH concentration with attention to the assumptions that define this relationship, the majority of false-positive results can be readily identified. If a free T4 anomaly remains unexplained on repeat sampling, it is appropriate to use an alternative free T4 method that depends on a different assay principle and to correlate the result with an authentic total T4 measurement.

Hydroxypropyl-beta-cyclodextrin as delivery system for thyroid hormones, regulating glutathione S-transferase expression in rat hepatocyte co-cultures

Thyroid hormones play a role in the regulation of glutathione S-transferase (GST) expression. Here, co-cultures of rat hepatocytes with bile duct epithelial cells have been used to study the direct effects of both triiodothyronine (T3) and thyroxine (T4) on GST activities and proteins. Because T3 and T4 are poorly water soluble and organic solvents used to dissolve them often interfere with biotransformation pathways, an alternative delivery system namely hydroxypropyl-beta-cyclodextrin (HPBC) has been applied. Appropriate control cultures contained either 0.02 or 0.10% (w/v) HPBC, the concentrations necessary to supply T3 and T4 (10(-9) to 10(-5) M) to the cells, respectively. No effect of the vehicle HPBC on the different GST isoenzyme activities and proteins could be observed. On the contrary, after 10 days of co-culture, T3 and T4 decreased GST protein concentrations as well as GST activities measured by 1-chloro-2,4-dinitrobenzene (broad spectrum), 1,2-dichloro-4-nitrobenzene (Mu class M1/M2-specific) and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (Alpha class A1/2-specific) in a concentration-dependent manner. The Alpha class subunits A1/2 and A3, and the Mu class subunit M2 were mostly affected. No effect was observed on the Pi class enzyme. These findings indicate that a combination of co-cultured hepatocytes with an HPBC-based delivery system for hydrophobic compounds represents a powerful in vitro tool in drug development.

Minor alterations in thyroid-function tests associated with diabetes mellitus and obesity in outpatients without known thyroid illness

Thyroid function tests might be affected by diabetes and obesity. To evaluate the influence of these parameters in routine conditions, 72 diabetic and 53 non-diabetic outpatients without known thyroid diseases or severe chronic illness were recruited over a 7-month period. For each patient, dosages of thyrotropin (TSH), total and free thyroxine (TT4 and FT4, respectively), total and free triiodothyronine (TT3 and FT3) and T3 resin uptake (T3RU) were performed by radioimmunoassays. The simultaneous influence of various parameters known to affect thyroid-function tests was evaluated by multivariate linear regression. The studied variables included gender, age, glucosteroids, estrogens, tobacco habits, iodine contacts, body mass index (BMI) and diabetes mellitus. Tobacco habits and iodine contacts did not influence any tests. As expected, estrogens induced an increase in TT4 and TT3 values (p < 0.001 and 0.020, respectively) associated with a decrease in T3RU (p < 0.001). Consequently, females had lower T3RU than males (p < 0.0001). Corticotherapy was associated with decreased TSH values (p = 0.022). TT3 and FT3 decreased with age (p < 0.001), whereas T3RU and FT4 increased (p = 0.020 and 0.004, respectively). In contrast to an increase in TSH (p = 0.006), TT4 and FT4 decreased at higher BMI levels (p = 0.018 and 0.004, respectively), which is consistent with subclinical hypothyroidism. In diabetic patients, TSH was lower than in nondiabetic subjects (p = 0.039). Thus, the present study indicates that besides known parameters such as age and drugs, thyroid-function tests can also be altered by diabetes mellitus and obesity.

An audit of total and free thyroxine measurements in screening for hypo and hyperthyroidism in patients using chemiluminescence immunoassay

An audit of 2509 patient specimens analyzed for both total thyroxine (TT4) and free thyroxine (FT4) by the ACS-180 automated chemiluminescence immunoassay analyzer revealed that there were 219 discrepancies (8.7% of the total). A discrepancy was defined as one analyte within its reference range and the other outside. The discrepant results were divided into 4 groups: group A: normal TT4, but decreased FT4, 101 patients (4.0%); group B: increased TT4, normal FT4, 78 patients (3.1%); group C: decreased TT4, normal FT4, 34 patients (1.4%); and group D: normal TT4, increased FT4, 6 patients (0.2%). TSH measurements were available, by a 3(rd) generation chemiluminescent assay, in 142 of these patients, and were consistent with the FT4 result in 72 patients, with TT4 in 61 cases and with neither in 9 patients. The clinical diagnosis was investigated in a subgroup of 43 endocrine patients. Thirteen of the 20 endocrine patients in group A were diagnosed as hypothyroid, with a measured serum TSH, in 11 of them, of median 14.6, range 1.2 to 46.2 μlU/ml. Eleven of the 19 endocrine patients in group B were on thyroid replacement, with a measured serum TSH, in 7 of them of <0.01 μlU/ml. The audit of current laboratory practice led to a suggestion to replace the current thyroid function screening strategy of measuring both TT4 and FT4 by the combination of FT4 and TSH. The reasons for the discrepancies and the alternative strategies for screening of thyroid function are discussed.

Reminders of Drug Effects on Laboratory Test Results

Drug effects on laboratory test results are difficult to take into account without an online decision support system. In this study, drug effects on hormone test results were coded using a drug-laboratory effect (DLE) code. The criteria that trigger the reminders were defined. To issue reminders, it was necessary to write a computer program linking the DLE knowledge base with databases containing individual patient medication and laboratory test results. During the first 10 months, 11% of the results from hormone samples were accompanied by one or more DLE reminders. The most common drugs to trigger reminders were glucocorticoids, furosemide, and metoclopramide. Physicians facing the reminders completed a questionnaire on the usefulness of the reminders. All respondents considered them useful. In addition, DLE reminders had caused 74% of respondents to refrain from additional, usually performed examinations. In conclusion, drug effects on laboratory tests should always be considered when interpreting laboratory results. An online reminder system is useful in displaying potential drug effects alongside test results.

Changes in thyroid function tests during short-term salsalate use

Although long-term administration of salsalate depresses blood levels of both total thyroxine (T4) and total triiodothyronine (T3) and at least transiently decreases serum thyrotropin (TSH), changes in thyroid function tests have not been fully characterized during its short-term use. It is also unclear if the observed changes are solely the result of decreased hormone binding to carrier proteins or if reduced hepatic 5'-monodeiodinase activity is important. Blood was sampled at baseline (day 0) and after 24 hours (day 1) and 72 hours (day 3) in eight subjects taking a therapeutic dose of salsalate 1,500 mg twice daily. Total T4 decreased from 90.1+/-7.7 nmol/L (mean+/-SD) on day 0 to 82.9+/-8.6 nmol/L on day 1 (P=.1 v baseline) and 68.6+/-8.7 nmol/L on day 3 (P=.0001). Total T3 decreased from 1.76+/-0.20 nmol/L to 1.61+/-0.16 nmol/L on day 1 (P<.05) and 1.31+/-0.27 nmol/L on day 3 (P=.002). The T4/T3 ratio was 51.7+/-7.7 at baseline and remained unchanged after 3 days. Levels of reverse T3 (rT3) were reduced from 0.24+/-0.05 nmol/L to 0.18+/-0.02 nmol/L on day 3 (P<.05). While the free T4 index (FTI) declined in parallel with total T4, the free T4 level by direct equilibrium dialysis (FTD) was unchanged after 3 days. Serum TSH decreased from 1.47+/-0.47 mU/L to 0.91+/-0.27 mU/L after 1 day (P<.05) and remained suppressed after 3 days (0.95+/-0.49 mU/L, P<.05). In conclusion, (1) therapeutic doses of salsalate significantly decrease serum concentrations of total T4, total T3, and rT3 to about 75% of baseline levels after 3 days without altering the T4/T3 ratio; (2) although the FTD does not change, serum TSH concentrations remain suppressed; and (3) the proportionate decrease in total thyroid hormone levels suggests that inhibition of hormone binding to serum proteins is more important in producing these changes than reduced hepatic 5'-monodeiodinase activity.

Salsalate and salicylate binding to and their displacement of thyroxine from thyroxine-binding globulin, transthyrin, and albumin

Salsalate and its metabolite salicylate are inhibitors of thyroid hormone binding to serum transport proteins and reduce serum total thyroxine (T4) and triiodothyronine (T3) in vivo. The present study is the first to examine and compare salsalate and salicylate binding to human thyroxine-binding globulin (TBG), transthyretin (TTR), albumin (ALB), and whole human serum, and displacement by salsalate and salicylate of T4 from isolated TBG, TTR, ALB. Salsalate and salicylate binding were studied by ultrafiltration at salsalate concentrations of 0.24-1.16 mM (62-300 microg/mL) and salicylate concentrations of 0.0375-2.25 mM (6.0-360 microg/mL). T4 displacement by salsalate and salicylate from TBG, TTR, and ALB was studied by equilibrium dialysis at salsalate concentrations of 0 to 1.52 mM (0-393 microg/mL) and salicylate concentrations of 0 to 60 mM (0-9600 microg/mL). In normal human serum, 95% of salsalate and 76% of salicylate were protein-bound. In the presence of isolated ALB, 89% of salsalate and 64% of salicylate were ALB-bound. Both salsalate and salicylate inhibited T4 binding to all 3 major T4 binding proteins. Both displaced proportionately more T4 from TBG compared with TTR and ALB. The principal site to which both salsalate and salicylate in serum is bound (ALB) is different from the principal site from which they displace T4 (TBG). Salsalate potency in displacing T4 from TBG and ALB was approximately 100-fold greater than salicylate potency.

Thyroid functions in lithium-treated psychiatric patients: a cross-sectional study

In the present cross-sectional study, thyroid functions (viz. thyroid radioiodine uptake [RAIU] and serum T3, T4, and thyroid-stimulating hormone [TSH]) were evaluated in 24 healthy controls and 132 outdoor affective disorder patients. Eleven of these patients were to receive lithium (Li) and the remaining 121 patients were at different stages of Li treatment ranging from 0.7 to 240 mo. RAIU was found to increase significantly throughout the Li therapy and was associated with the corresponding rise in TSH levels. In totality, Li treatment induced subclinical hypothyroidism in 51/132 (39%) of patients. However, 8/51 patients who belonged to known iodine-deficient belt had abnormally high TSH (range 15.2-76.0 microIU/mL), low T4 (5.3+/-2.5 microg/dL), and normal T3 and at least 4 of these 8 patients were clinically hypothyroid. T4 levels declined significantly (p < 0.05) with Li treatment ranging from 61 to 240 mo as compared to the corresponding values in the pre-Li group. The T3/T4 ratio was found to be significantly higher with Li treatment ranging from 0.7 to 6 mo in comparison with the pre-Li group and this value returned to base levels after long-term Li therapy. High T3 and T4 were observed in 13% and 12% of the patients, respectively, as compared to the corresponding control values.

Role of colestipol in the treatment of hyperthyroidism

The enterohepatic circulation of thyroxine (T4) and triiodothyronine (T3) is higher in thyrotoxicosis. Bile-salt sequestrants bind iodothyronines and thereby increase their fecal excretion. We, therefore, evaluated the effect of colestipol-hydrochloride administration on clinical and biochemical indices of patients with hyperthyroidism. In a prospective, controlled trial, ninety-two adult volunteers with Graves' disease, toxic autonomous nodule or toxic multinodular goiter were randomly assigned into the following treatment protocols: Group 1, 30 mg of methimazole (MMI) and 20 g of colestipol-hydrochloride (COL) daily; Group 2, 30 mg of MMI daily; and Group 3, 15 mg of MMI 20 g of COL daily. The patients were further classified into Group A, severe hyperthyroidism (baseline levels of total T3 (TT3) > or =5 nmol/l) and Group B, mild to moderate thyrotoxicosis (baseline levels of TT-3<5 nmol/l). Crook's clinical index, serum free T4 (FT4), TT3 and thyroid stimulating hormone (TSH) levels were determined before (WO), following one week (W1) and two weeks (W2) of treatment. Serum TT3 level decreased (mean+/-SE) at W1 by 40.8+/-2.6% of WO in Group1 and by 29.2+/-2.4% in Group 2 (p<0.001), and down further to 47.8+/-3.0% at W2 in Group 1, and 40.6+/-2.8% in Group 2 (p=0.01). Serum FT4 level decreased (mean+/-SE) from WO to W1 by 31.7+/-2.7% in Group 1 and by 16.2+/-3.1% in Group 2 (p=0.005), and down to 49.1+/-2.8% of WO at W2 in Group 1 and to 38.7+/-3.5% in Group 2 (p=0.07). In sub groups B COL was not effective in reducing thyroid hormone levels nor in ameliorating the clinical status of the patients. However, in Group A3 COL lowered FT4 (p=0.001) and TT3 (p=0.05) levels as compared to group A2. At W2 the clinical hyperthyroidism score improved faster in Group A1 (p<0.001) and Group A3 (p=0.012) as compared to the control Group A2. In conclusion, COL is an effective and well tolerated adjunctive agent in the treatment of hyperthyroidism. Its main effect is in severe cases of thyrotoxicosis, and in the first phase of treatment. As adjunctive COL treatment in hyperthyroidism allows reducing MMI dosage it may decrease the rate of dose dependent MMI side effects.

Subclinical thyroid disease in the elderly

The development of sensitive assays for thyrotropin (TSH) has led to the discovery that many older patients have abnormal TSH levels without other alterations in serum thyroid hormone levels, conditions termed subclinical hypothyroidism (isolated elevation of TSH levels) and subclinical hyperthyroidism (isolated suppression of TSH levels). Subclinical hypothyroidism occurs in 5% to 10% of elderly subjects, and is especially prevalent in elderly women. Subclinical hyperthyroidism is less common, affecting less than 2% of the elderly population. The causes of subclinical thyroid disease in the elderly are similar to those of thyroid disease in the general population, although medications and iodine-containing compounds may play an increased role. Potential risks of subclinical hypothyroidism in the elderly include progression to overt hypothyroidism, cardiovascular effects, hyperlipidemia, and neurological and neuropsychiatric effects. Potential risks of subclinical hyperthyroidism in the elderly include progression to overt hyperthyroidism, cardiovascular effects (especially atrial fibrillation), and osteoporosis. Decisions to treat elderly subjects with subclinical thyroid disease should be based on a careful assessment of these risks in the individual patient.

Psychoneuroendocrinology of mood disorders. The hypothalamic-pituitary-thyroid axis

Abnormal thyroid functioning can affect mood and influence the course of unipolar and bipolar disorder. Even mild thyroid dysfunction has been associated with changes in mood and cognitive functioning. Thyroid hormone supplementation may have role in the treatment of certain mood disorders, particularly rapid-cycling bipolar disorder. Women are more vulnerable to thyroid dysfunction than men and also respond better to thyroid augmentation. This article reviews the relationship between thyroid function and mood, and the use of thyroid hormones in the treatment of mood disorders. The impact of gender on these issues is also discussed.

Iodine-induced hyperthyroidism: occurrence and epidemiology

We have critically reviewed the available information on iodine-induced hyperthyroidism (IIH) from published sources and other reports as well as the experience of the authors in Tasmania, Zaire, Zimbabwe, and Brazil. Administration of iodine in almost any chemical form may induce an episode of thyrotoxicosis (IIH). This has been observed in epidemic incidence in several countries when iodine has been given as prophylaxis in a variety of vehicles, but the attack rate as recorded has been low. IIH is most commonly encountered in older persons with long standing nodular goiter and in regions of chronic iodine deficiency, but instances in the young have been recorded. It customarily occurs after an incremental rise in mean iodine intake in the course of programs for the prevention of iodine deficiency, or when iodine-containing drugs such as radiocontrast media or amiodarone are administered. The biological basis for IIH appears most often to be mutational events in thyroid cells that lead to autonomy of function. When the mass of cells with such an event becomes sufficient and iodine supply is increased, the subject may become thyrotoxic. These changes may occur in localized foci within the gland or in the process of nodule formation. IIH may also occur with an increase in iodine intake in those whose hyperthyroidism (Graves' disease) is not expressed because of iodine deficiency. The risks of IIH are principally to the elderly who may have heart disease, and to those who live in regions where there is limited access to medical care. More information is needed on the long-term health impact of IIH or "subclinical" IIH, especially in the course of prophylaxis programs with iodized salt or iodinated oil in regions where access to health care is limited.

Computerized monitoring of potentially interfering medication in thyroid function diagnostics

OBJECTIVE

Many drugs are known to affect the results of laboratory tests. This may cause problems in the interpretation of clinical laboratory data and lead to wrong diagnoses, unnecessary further tests and additional costs. A computerized monitoring system of potential drug effects on laboratory tests was developed in Turku University Central Hospital. In the present study the incidence and nature of potentially interfering drug effects in thyroid function diagnostics was examined in order to ease the clinical implementation of the system.

METHODS

Computerized medication data of 754 hospital in-patients whose thyroid function was tested were combined with a knowledge base of drug effects on laboratory tests. All medications that potentially affected the levels of serum thyrotropin or free thyroxin in study patients were detected.

RESULTS

40% (292 of 735) of the patients tested for thyrotropin and 32% (107 of 333) of the patients tested for free thyroxin received potentially interfering medication during the tests. The most common potentially interfering medication was acetylsalicylic acid, but the daily dose was usually low, 100 mg.

CONCLUSIONS

The coincidence of potentially interfering medication and thyroid function tests was substantial. On-line hints of drug effects on thyroid function tests might offer valuable decision support to clinicians, but further development of the system is needed to regulate the prevalence of warnings into a clinically optimal level.

The diagnosis and treatment of subclinical hypothyroid states in depressed patients

The diagnosis and treatment of subclinical hypothyroidism in mood-disordered patients is complex and somewhat controversial. The psychiatrist must recognize that such subclinical states may contribute to depression, mood cycling, or delayed response to treatment if undetected. Autoimmune thyroiditis, which may ultimately lead to various grades of hypothyroidism, may also be seen in depressed populations, particularly in postpartum females. The author discusses these issues by means of a clinical vignette, then proposes an algorithm for the diagnosis and treatment of hypothyroid states in mood disordered populations.

Multiple fixed doses of "Seroquel" (quetiapine) in patients with acute exacerbation of schizophrenia: a comparison with haloperidol and placebo. The Seroquel Trial 13 Study Group

Five fixed doses of the atypical antipsychotic "Seroquel" (quetiapine) were evaluated to delineate a dose-response relationship, as measured by changes from baseline in Brief Psychiatric Rating Scale (BPRS), Clinical Global Impression (CGI), and Modified Scale for the Assessment of Negative Symptoms (SANS) summary scores, and to compare efficacy and tolerability opposite placebo and haloperidol. Three hundred sixty-one patients from 26 North American centers entered this double-blind, placebo-controlled trial with acute exacerbation of chronic schizophrenia (DSM-III-R). Patients who completed a single-blind, placebo washout phase were randomized to double-blind treatment with quetiapine (75, 150, 300, 600, or 750 mg daily), haloperidol (12 mg daily), or placebo and evaluated weekly for 6 weeks. At end point, significant differences (p < 0.05, analysis of covariance) in adjusted mean changes from baseline were identified between the four highest doses of quetiapine and placebo for BPRS total, BPRS positive-symptom cluster, and CGI Severity of Illness item scores and between quetiapine 300 mg and placebo for SANS summary score. Differences between quetiapine and haloperidol were not significant. Dose-response modeling showed significant linear and quadratic functions of quetiapine dose for all primary efficacy variables. Notably, no significant safety concerns were identified as dose increased. Quetiapine was no different from placebo across the dose range studied regarding incidence of extrapyramidal symptoms or change in prolactin concentrations. Quetiapine is well tolerated and clinically effective in the treatment of schizophrenia. It is both superior to placebo and comparable to haloperidol in reducing positive symptoms at doses ranging from 150 to 750 mg/day and in reducing negative symptoms at a dose of 300 mg/day.

Thyroid diseases in the elderly

The ageing thyroid is associated with a number of morphological and functional changes, such as decreased serum T3 and mean thyroid-stimulating hormone concentrations, that are to some extent independent of intercurrent non-thyroidal illnesses. All thyroid diseases, including clinical and subclinical hypo- and hyperthyroidism, non-toxic nodular goitre and thyroid cancer, are encountered in the elderly, but their prevalence and clinical expression differ from those observed in younger patients. In the elderly, autoimmune hypothyroidism is particularly prevalent, hyperthyroidism is mainly characterized by cardiovascular symptoms and is frequently due to toxic nodular goitres, and differentiated thyroid carcinoma is more aggressive. The interpretation of thyroid function tests is difficult in old individuals, because of age-associated changes in thyroid function and frequent alterations secondary to non-thyroidal illnesses and/or drugs. Treatment of thyroid disease deserves special attention in old patients because of the increased risk of complications.

Effects of ramipril on the hormone concentrations in serum of hypertensive patients

The effects of the angiotensin-converting enzyme inhibitor ramipril on thirteen endocrinological tests were evaluated. These tests comprised serum follitropin, lutropin, prolactin, thyrotropin, free thyroxine, total thyroxine, free triiodothyronine, parathyrin, cortisol, testosterone, sex hormone binding globulin, androstenedione and dehydroepiandrosterone sulphate. Eleven hypertensive outpatients, 9 men and 2 women, treated at the department of internal medicine in Turku University Central Hospital, received 5 mg of ramipril once a day for the study period of four weeks. The above mentioned endocrinological tests were performed before and at the end of the ramipril treatment. Ramipril decreased the value of free thyroxine statistically significantly, p = 0.011, from the mean value of 17.1 pmol/l to the mean value of 16.0 pmol/l when measured with Amerlex-MAB* free thyroxine kit. The mean within-subject difference was -1.10 pmol/l with a 95% confidence interval of -1.87 - -0.33 pmol/l. With the AutoDELFIA free thyroxine kit and with the reference method dialysis+RIA no effect was detected. Other endocrinological tests examined were not affected by ramipril. Since the decreasing effect of ramipril on free thyroxine was detected only with Amerlex-MAB* but neither with AutoDELFIA nor with dialysis+RIA, the effect was concluded to be analytical. The underlying mechanism and the component ultimately interfering with the analysis is unknown.

Maternal thyroid function: interpretation of thyroid function tests in pregnancy

Thyroid status is frequently assessed during pregnancy, both to evaluate suspected thyroid abnormalities, and to monitor the status, of pre-existing thyroid disease. However, the production, circulation, and disposal of thyroid hormone are all altered in pregnancy. Interpretation of thyroid function studies in the pregnant patient must be performed based on an understanding of the normal physiologic changes at each stage of pregnancy. Examples of pregnancy-associated changes include, estrogen-stimulated increase in serum thyroxine binding globulin, chorionic gonadotropin stimulated T4 and T3 production from the thyroid gland, and accelerated degradation of thyroid hormone by the placenta. The serum-TSH alone is usually not adequate to assess thyroid status in pregnancy, and the various conditions that can effect this measurement are described. The pattern of thyroid studies in pregnancy is important in diagnosing thyroid disease, and it may indicate physiologic adaptations to optimize maternal thyroid status for fetal development.

Fetal thyroid function: diagnosis and management of fetal thyroid disorders

The fetal hypothalamic-pituitary-thyroid axis develops independently of the maternal axis, but it is dependent on the maternal-placental system for adequate supply of iodide substrate. This iodide is supplied by direct transfer of maternal plasma iodide and by placental deiodination of T4. In addition, although placental transport of iodothyronines is limited, significant maternal-fetal transfer of T4 occurs, accounting for approximately 30% of the average 10 ug/dL serum-T4 concentration in fetal-cord blood at term. Current information suggests that this maternal contribution to the fetal-T4 levels is important for normal fetal maturation, particularly of the central nervous system. Combined maternal-fetal hypothyroxinemia can lead to irreversible fetal central nervous system damage. The timing of this fetal T4 dependency is not clear. It may be important in the first half of gestation, before the fetal thyroid gland is capable of T4 production, as well as the latter half of gestation when thyroid hormone effects on multiple organ systems are developing. Management of fetal thyroid dysfunction requires normalization of maternal serum T4 concentrations, avoidance or careful monitoring of potentially goitrogenic drug effects in the fetus, and in some instances, direct or indirect fetal therapy. In most cases fetal hypothyroidism is sporadic and undetected, and prognosis for normal growth and development is excellent if the mother is euthyroid and the hypothyroid state is detected and adequately treated at birth. Fetal treatment by intraamniotic thyroxine injection has been provided in cases of inadvertent maternal radioiodine treatment of Graves' disease between 10 and 20 weeks gestation and for fetal goiter detected by ultrasound. Effective treatment of fetal hyperthyroidism in pregnant women with high titers of thyroid stimulating autoantibody is possible by judicious administration of antithyroid drugs to the mother. Management of the hyperthyroid state in the neonate also is essential.

The direct effects of thyroid hormones on rat mesenteric resistance arteries

The direct relaxant effects of thyroid hormones on mesenteric resistance vessels were investigated using an isometric wire myograph. Both the L- and the D-isomers of thyroxine (T4) and triiodothyronine (T3) were studied. In contrast with the long-term effects of thyroid hormones, both T4 enantiomers proved more potent in inducing vascular relaxation than the two T3 enantiomers. The interaction between thyroid hormones and calcium-induced contractions was studied. T4 concentration dependently inhibited the Ca2+ induced contractions, showing noncompetitive interaction. Furthermore, we investigated whether the endothelium was involved in the relaxant effect to L-T4. The T4 induced relaxation proved impaired by prior incubation with the nitric oxide (NO) inhibitor N-omega-nitro-L-arginine methylester HCl (L-NAME, 0.1 microM), indicating that T4 is able to stimulate the production of endothelium-derived NO. L-T4-induced relaxation was enhanced by prior incubation with indomethacin (10 microM), whereas in endothelium-denuded preparations an unaltered response was found. The present results indicate that L-T4-induced relaxation is established by an indirect effect via the endothelium and by a direct effect on vascular smooth muscle cells, possibly by influencing calcium fluxes. Because vascular relaxation is established at supraphysiologic concentrations (approximately 100 times the basal level) of thyroid hormone, it is concluded that the direct effect of thyroid hormone on mesenteric vascular smooth muscle cells are not relevant for the in vivo situation.

Endocrinologic complications of HIV infection

A variety of endocrine disorders occur in HIV-infected patients. The abnormalities may be a consequence of HIV infection, or may result from opportunistic infections, associated malignancies, illness-associated cytokine production, or use of therapeutic agents. Observations and controversies concerning adrenal, gonadal, thyroidal, and metabolic abnormalities are discussed. Heightened awareness of problems that might otherwise be overlooked will permit timely diagnosis and treatment of identified problems, which will enhance and potentially prolong the lives of people infected with HIV.

Medication use in the hypothyroid patient

Hormones produced by the thyroid gland are essential for normal growth, maturation, and regulation of all organ systems. In hypothyroidism, the thyroid gland fails to secrete adequate amounts of thyroid hormone. As a consequence there is a slowing of all body processes. Hypothyroidism occurs in 2% of women and 0.2% of men. The incidence increases with age; among people older than 60 years of age, 6% of women and 2.5% of men have abnormal thyroid function test values indicative of the condition. The incidence of subclinical hypothyroidism may approach 15% in persons 60 years of age or older. This finding is significant because within 4 years of diagnosis, subclinical hypothyroidism progresses to overt hypothyroidism in 20% to 40% of patients.