Lithium-induced Hypothyroidism Research Articles

Unraveling the Diagnostic Implications of Elevated Prealbumin Levels in Lithium-Induced Hypothyroidism: A Case Report

Prealbumin, a multifunctional protein synthesized primarily in the liver, serves as a critical biomarker in clinical practice, offering insights into nutritional status and prognostic outcomes. While its precise physiological role remains incompletely understood, prealbumin is known to facilitate hormone transport, particularly of thyroxine, and contribute to neuroprotection. Clinically, prealbumin levels are sensitive indicators of recent changes in protein intake and absorption, making them invaluable in guiding therapeutic interventions. Alterations in prealbumin levels have been associated with various medical conditions, including chronic kidney disease, liver disease, and cancer, emphasizing its prognostic significance across diverse clinical contexts. we report a case of a 42-year-old male with bipolar disorder managed on lithium therapy, presenting with depressive symptoms and unexpected hyperprealbuminemia. Subsequent investigation revealed primary hypothyroidism secondary to lithium intoxication, highlighting the intricate relationship between lithium therapy, prealbumin levels, and thyroid dysfunction. We discuss the mechanisms and clinical implications of lithium-induced hypothyroidism, emphasizing the importance of considering thyroid function in patients with elevated prealbumin levels. This case underscores the necessity for vigilant monitoring and timely intervention to optimize patient outcomes in cases of lithium-induced thyroid dysfunction. Continued research is crucial for elucidating the complex interactions between prealbumin, lithium therapy, and thyroid function, enhancing our understanding and management of these metabolic disturbances.

Low and very low lithium levels: Thyroid effects are small but still require monitoring.

Low doses of lithium, as might be used for mood or dementia prevention, do not carry the same renal, toxicity, and tolerability problems of doses used for prophylaxis or treatment of mania. However, thyroid effects of low doses have not been investigated. Our goal in this study was to assess the changes in thyroid-stimulating hormone (TSH) associated with a broad range of lithium levels, including those well below the therapeutic range for bipolar disorders. This study was conducted in a small healthcare system with 19 associated primary care clinics served by a Collaborative Care program of psychiatric consultation. In this retrospective review of electronic records, we searched for patients who had received a lithium prescription and both pre- and post-lithium thyroid-stimulating hormone (TSH) levels. Patients with low lithium levels (<0.5 mEq/L, N = 197) had a mean thyroid-stimulating hormone (TSH) increase of 0.52 mIU/L. Patients with maintenance lithium levels (0.5-0.8 mEq/L; N = 123) had a mean TSH increase of 1.01 mIU/L; and patients with antimanic lithium levels (>0.8 mEq/L; N = 79) had a mean TSH increase of 2.16 mIU/L. The probability of TSH exceeding the upper limit of normal in our laboratory (>4.2 mIU/L) was positively associated with pre-lithium TSH. These results suggest that the risk of lithium-induced hypothyroidism is dose-related, and relatively small with very low doses, but thyroid monitoring, including a pre-lithium TSH, is still warranted.

Lithium-induced Thyroid Dysfunction and the Duration of Lithium Treatment in Patients with Bipolar Disorder.

Introduction Negative impact of long-term lithium treatment on kidney and thyroid functions makes the important problem of such therapy. While kidney functions deteriorate in time-dependent manner after ten years of lithium therapy it is unclear whether a significant association exists between thyroid dysfunction and duration of lithium administration. Aims The aim was to compare thyroid hormones and antibodies in bipolar patients receiving lithium for 10-19 years with those receiving for 20 years or more. Methods The cross-sectional study was performed on 66 patients (21 male, 45 female) with bipolar mood disorder, receiving lithium for 10-44 (20 + 9) years. Thyroid stimulating hormone (TSH), free thyroxine (fT3) and free triiodothyronine (fT4) as well as thyroid peroxidase (TPO), thyroglobulin (TG) and TSH receptor (TSH-R) antibodies were measured. Results Features of hypothyroidism were found in 10 (22%) female patients but not in male patients. A significant percentage of patients had abnormally high anti-TPO, and anti-TG antibodies (45% and 65%, respectively). There were no differences in thyroid function between 38 patients receiving lithium for 10-19 years and 28 patients taking the drug for 20 years or more. Conclusions The results confirm greater susceptibility of female bipolar patients for lithium-induced hypothyroidism. High anti-TPO and anti-TG antibodies suggest a possibility of autoimmune disturbance in these subjects. However, in contrast to lithium effect on kidney function, our results do not show an association between duration of long-term lithium therapy and thyroid dysfunction.

Anti-thyroid Antibodies in Bipolar Disorder

Dysfunction of the hypothalamus-pituitary-thyroid axis has been shown to play a role in the pathophysiology of bipolar disorder. Autoimmune thyroiditis is the most common cause of thyroid function alteration. Thus, auto-immune thyroiditis is likely associated with bipolar disorder. It might influence its course, prognosis and/or management. To study the prevalence of positive anti-thyroid antibodies in patients with bipolar disorder and to examine the prognostic and the therapeutic implications of their presence. Literature was reviewed using the Medline database and the following keywords: ‘bipolar disorder” ‘antithyroid antibodies” ‘thyroiditis”. PubMed research returned 12 results. After manual inspection, 10 articles were retained and examined. The prevalence of positive antithyroperoxydase antibodies (anti-TPO Abs) is higher in bipolar patients than in healthy controls, reaching 27%. The presence of positive anti-TPO Abs has been associated with rapid-cycling, with a higher risk of lithium-induced hypothyroidism as well as with poor prognosis. Auto-immune thyroiditis appears to be related not only to bipolar disorder itself but also to the genetic vulnerability to develop the disorder. The presence of anti-TPO Abs is a possible endophenotype for bipolar disorder. Anti-TPO Abs should be obtained in many patients with bipolar disorder, especially in those on lithium.

Lithium-Induced Hypothyroidism: Oxidative Stress and Osmotic Fragility Status in Rats

The present study was conducted to explore the possible effects of different doses of lithium carbonate on thyroid functions, erythrocyte oxidant-antioxidant status, and osmotic fragility. Twenty-four Wistar-type male rats were equally divided into three groups: groups I and II received 0.1 and0.2% lithium carbonate in their drinking water, respectively, for 30days. The rats in group III served as controls, drinking tap water without added lithium. At the end of the experimental period, the erythrocyte osmotic fragility and the levels of triiodothyronine (T3), thyroxine (T4), thyroid-stimulating hormone (TSH), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione (GSH) were measured in blood samples. Compared to controls, there was a statistically significant increase of TSH but decreases of the T3 and T4 levels in group II. Both experimental groups showed a statistically significant increase of the maximum osmotic fragility limit. The minimum osmotic fragility values of the animals in group II were statistically higher than those of controls. The standard hemolytic increment curve of both experimental groups was shifted to the right when compared to the curve obtained from the controls. Also, relative to controls, the activities of MDA and SOD were significantly higher and the GSH level lower in group II, but not so in group I. The results of the present study show that treatment with lithium carbonate may result in thyroid function abnormalities, increased oxidative damage, and possible compromise of the erythrocyte membrane integrity resulting from increased osmotic fragility.

Sarcoidosis of the thyroid: A case report and review of the literature

Results: 67 year old male with lithiuminduced hypothyroidism and sarcoidosis presented with a thyroid nodule. Fine needle aspiration biopsy demonstrated atypical cellular features with epithelioid histiocytes found in loose syncitial aggregates and a background of lymphocytes, findings concerning for possibile papillary thyroid carcinoma. The final pathology from his thyroidectomy revealed multiple nodules and replacement of thyroid tissue with chronic inflammatory cells and a scattering of multiple well-formed interstitial non-caseating granulomas composed of epithelioid histiocytes, a mixed inflammatory infiltrate, and multinucleated giant cells. A lymph node further demonstrated multiple interstitial non-caseating granulomas composed of epithelioid histiocytes surrounded by mixed inflammatory infiltrate and multinucleated giant cells. The final diagnosis was sarcoidosis of the thyroid.

Bipolar Disorder and Pregnancy: Maintaining Psychiatric Stability in the Real World of Obstetric and Psychiatric Complications

This article describes complex, real-life issues faced by a woman with bipolar I disorder who wished to bear a healthy child while remaining psychiatrically well. The therapeutic issues include balancing treatment decisions that affect fetal and maternal risks. The authors address the importance of carefully considering the patient’s history of response to medications when evaluating risks to maternal and fetal health. They discuss the role of the psychiatrist as a part of the treatment team faced with unpredictable but not unexpected complexities, such as miscarriage, abnormal or questionable prenatal screening tests, gestational diabetes, and the emergence of fetal decelerations, preterm labor, and psychiatric decompensation. The article presents and evaluates treatment decisions made in the setting of multiple obstetric and psychiatric complications that do not clearly fit published algorithms. The importance of incorporating family and social supports as an integral part of the treatment plan is emphasized.

Lithium use in special populations

Byline: E. Mohandas, V. Rajmohan Lithium, a monovalent cation, was first used for the treatment of mania in the 1940s. Half a century into its use, the drug continues to be the preeminent choice for bipolar disorder with antimanic, antidepressant (modest) and antisuicidal property. Lithium is the "gold standard" mood stabilizer against which potential mood stabilizer agents are judged. The therapeutic uses of lithium also include use as an augmenting agent in depression, schizoaffective disorder, aggression, impulse control disorder, eating disorders, attention deficit disorder and in certain subsets of alcoholism. Lithium has been used in many medical disorders, especially cluster headache and dermatological disorders (seborrheic dermatitis, eczematoid dermatitis, genital herpes).[sup] [1] The drug is however associated with neurologic, endocrine, cardiovascular, renal, dermatologic and gastrointestinal adverse effects and possible teratogenicity. History Lithium was first discovered and defined by Johan August Arfvedson in 1817 when he did an analysis of the mineral petalite [LiAl(Si2O5)2]. Petalite was first found by Brazilian scientist Jose Bonifacio Andrade e Silva in 1800. Lepidolite, spodumene, petalite and amblygonite are the more important minerals containing lithium. It was Arfwedson's laboratory chief John Jacob Berzelius who named this alkali metal "lithion." Arfvedson was never able to fully isolate lithium, and it wasn't until 1855 that it was isolated by William Thomas Brande. Brande and Sir Humphrey Davy earlier had done electrolysis on lithium oxide in 1818. Lithium was first produced commercially in 1923 by Metallgesellschaft AG.[sup] [2] The use of lithium for medicinal purposes can be traced back 1,800 years to the Greek physician Galen, who treated patients with mania by having them bathe in alkaline springs and drink the water, which probably contained lithium. In 1843 Alexander Ure introduced lithium into modern medicine, and he showed the in vitro reduction of weight of a uric acid bladder stone in a lithium carbonate solution. Sir Alfred Garrod later discovered that gouty uric acid deposits also were soluble in lithium solution. The view in that time was that uric acid imbalances caused a wide range of diseases, and Armand Trousseau and Alexander Haig proposed that mania and depression also may result from this imbalance and lithium may be effective in these conditions. In the 1840s, lithium was mixed with carbonate or citrate to form a salt and was used to treat gout, epilepsy, diabetes, cancer and insomnia. In the 1870s, the then American Surgeon General William Hammond had provided anecdotal evidence for the use of lithium bromide in the treatment of acute mania. In the 1880s and 1890s the Lange brothers Carl and Fritz used lithium in depression, and Carl Lange was the first to systematically use lithium in the acute and prophylactic treatment of depression.[sup] [2] The introduction of lithium preparations and tablets in the 1900s brought to the fore the toxic effects of the drug; and there were reports of weakness, tremor, diarrhea, vomiting and deaths. The drug disappeared from the British Pharmacopoeia by 1932, but later in the 1940s it was used as a sodium substitute in low sodium diets; but the reports of severe intoxication led to its removal from American markets in 1949. [sup] [1] The appearance in 1949 in the Medical Journal of Australia of a paper entitled "Lithium salts in the treatment of psychotic excitement" by John F. J. Cade was an unspectacular entry into a new era of psychiatry. Manic patients showed improvement, with the patient becoming calmer after four to five days. There was no improvement in the excited schizophrenic patients, though there was a calming effect. There was no improvement or deepening of depression. The paper also gave details of initial dosage, maintenance doses, appearance of toxic symptoms and warning about lithium over-dosage. …

New Thyroxine Treatment in Older Adults Beginning Lithium Therapy: Implications for Clinical Practice

The authors sought to determine the incidence of lithium-induced hypothyroidism in a population-based cohort of older adults beginning lithium therapy and thereby to inform clinical guidelines on the frequency of monitoring necessary in this group. The authors conducted a population-based observational cohort study using four administrative databases that contained information on over 1.3 million older adults in Ontario who receive universal healthcare coverage in terms of physician services, drugs, and hospitalizations. Over an 18-month period, they studied adults age>or=65 who were newly prescribed lithium or valproate, monitoring subjects for initiation of T4 therapy (as a proxy for hypothyroidism) while they continued their lithium use. The authors identified 1,705 new users of lithium and 2,406 new users of valproate with similar baseline characteristics. Lithium users were significantly more likely to be treated with T4 than were valproate users. The rate of T4 treatment per 100 person-years was 5.65 in the lithium group and 2.70 in the valproate group. T4 treatment was initiated in almost 6% of lithium-treated patients, suggesting the possibility that hypothyroidism developed twice as frequently among these patients as would be expected among a mixed-age population. Increased vigilance and continued monitoring of thyroid functioning for at least 2 years is necessary in older adults beginning lithium therapy.

New Thyroxine Treatment in Older Adults Beginning Lithium Therapy: Implications for Clinical Practice

Objective The authors sought to determine the incidence of lithium-induced hypothyroidism in a population-based cohort of older adults beginning lithium therapy and thereby to inform clinical guidelines on the frequency of monitoring necessary in this group. Methods The authors conducted a population-based observational cohort study using four administrative databases that contained information on over 1.3 million older adults in Ontario who receive universal healthcare coverage in terms of physician services, drugs, and hospitalizations. Over an 18-month period, they studied adults age ≥65 who were newly prescribed lithium or valproate, monitoring subjects for initiation of T 4 therapy (as a proxy for hypothyroidism) while they continued their lithium use. Results The authors identified 1,705 new users of lithium and 2,406 new users of valproate with similar baseline characteristics. Lithium users were significantly more likely to be treated with T 4 than were valproate users. The rate of T 4 treatment per 100 person-years was 5.65 in the lithium group and 2.70 in the valproate group. Conclusion T 4 treatment was initiated in almost 6% of lithium-treated patients, suggesting the possibility that hypothyroidism developed twice as frequently among these patients as would be expected among a mixed-age population. Increased vigilance and continued monitoring of thyroid functioning for at least 2 years is necessary in older adults beginning lithium therapy.

Erythrocyte Glutathione Levels in Lithium-Induced Hypothyroidism

Lithium, widely used in the prophylaxis of psychiatric patients with bipolar affective disorders, is well known to induce thyroid alterations. However, a possible metabolic linkage between blood thyroxine levels and its regulatory function on erythrocyte glutathione concentration has not yet been evaluated in lithium-treated patients. The aim of this study was to assess the antioxidative capacity of erythrocytes in lithium-induced hypothyroidism before and after thyroxine replacement. Thyroid ultrasound with clinical and laboratory evaluation of thyroid function and thyroid-stimulating hormone assay were performed prior to and at 6-month intervals during lithium prophylaxis in 76 patients with bipolar affective disorders. The daily lithium dosage was adjusted to 600-1200 mg and the mean duration of treatment was 2.2 +/- 0.4 years. Final assessment revealed that 12 patients had evidence of primary hypothyroidism, and these were assigned as the test group. Lithium prophylaxis was supplemented with thyroxine at a dosage of 100 mg/day within 6 months after thyroid dysfunction was diagnosed. Red blood cell superoxide dismutase activities and the glutathione contents were measured before and after thyroxine replacement. In order to assess the effect of long-term lithium administration on red blood cell glutathione and superoxide dismutase levels, 12 patients who had not developed hypothyroidism during the follow-up period were selected for the lithium-treated euthyroid group. Mann Whitney U-test and Wilcoxon rank sum W-test were used for comparison of data. A comparison of the lithium-treated test group with healthy volunteers and their own values after thyroxine replacement revealed a significant decrease in red blood cell glutathione concentrations (p = 0.000) in the hypothyroid state. However, no clinically significant changes were observed in red blood cell superoxide dismutase activities of the test group. A statistical survey also demonstrated that there was no significant difference in the thyroid-stimulating hormone values as well as the red blood cell glutathione contents or superoxide dismutase activities between healthy controls and lithium-treated euthyroid subjects. It is most likely that lithium primarily inhibited hormone production in the thyroid and that this led to a compensatory increase in thyroid-stimulating hormone secretion with a significant decrease in the red blood cell glutathione content. While the red blood cell glutathione content of hypothyroid patients was reduced to 40% of the post-thyroxine level, unchanged superoxide dismutase activity might render the erythrocytes vulnerable to oxidative stress and ultimately haemolysis. Thyroxine replacement during lithium prophylaxis of psychiatric patients is advisable in order to prevent subclinical hypothyroidism and related defects of erythrocyte antioxidant capacity.

Elevated Thyrotropin in Bipolar Youths Prescribed Both Lithium and Divalproex Sodium

To examine the effect of combined lithium and divalproex sodium on thyroid-stimulating hormone (TSH) levels in children and adolescents with bipolar disorders and to identify risk factors for lithium-induced hypothyroidism. Bipolar youths aged 5 to 17 years participating in an open-label clinical trial received treatment with lithium and divalproex sodium for up to 20 weeks. TSH levels were measured at baseline and at the end of the study. Subjects were divided into two groups for analysis: group 1 had TSH levels of less than 10.0 mU/L at the end of the study and group 2 had TSH levels of 10.0 mU/L or more at end of the study. Twenty of the 82 subjects (24.4%) showed TSH elevations of at least 10 mU/L within an average exposure of less than 3 months. The mean baseline TSH level for group 2 was significantly higher than for group 1 (2.97 [SD = 1.48] versus 2.05 [SD = 0.89], p <.05). Mean lithium levels at the end of the study were 1.00 mEq/L for group 2 compared to 0.76 mEq/L for group 1 (t = -2.41, p =.019). Lithium is associated with significant rates of thyrotropin elevation in bipolar youths. Factors associated with elevation in TSH in lithium-treated subjects include a higher baseline TSH level and a higher lithium level. Close monitoring of thyroid function in children and adolescents taking lithium is recommended.

Lithium-Induced Hypothyroidism: More Prevalent Than Thought?

Treatment with lithium has been reported to produce hypothyroidism in 2% to 5% of treated patients. However, most studies have been conducted on a

Women at greater risk for lithium-induced hypothyroidism than men

Women at greater risk for lithium-induced hypothyroidism than men

Thyroid disorders in lithium-treated patients

Background : Little is known about the rate of thyroid disorders prior to lithium treatment, and which patients have a higher risk for developing such disorders during such treatment. Method : Assessment of the thyroid histories and laboratory results of 209 lithium-treated patients with affective disorders from one catchment area. Results : Six female patients had thyrotoxicosis before starting lithium, a rate of 4.9%. Twenty patients developed hypothyroidism during the treatment: 3.4% of all males and 14.9% of all females. Female patients over the age of 50 were more likely to develop early lithium-induced hypothyroidism. Conclusions : (1) Female patients with affective disorders might have an increased rate of thyrotoxicosis. (2) Lithium-induced hypothyroidism might develop earlier in female patients over the age of 50. Limitations : Retrospective design of the study. Clinical relevance : (1) The thyroid status of patients with affective disorders might be more relevant than is appreciated. (2) Guidelines for thyroid tests in lithium-treated patients should reflect the different risks conferred by age and gender.

Women with bipolar illness: clinical and research issues.

The purpose of this article is to review the literature concerning gender differences in the course of bipolar illness and discuss issues relevant to the treatment of women with the illness. The literature concerning the following topics is reviewed: gender differences in the course of bipolar illness; effects of the female reproductive cycle on the course of bipolar illness; special considerations in the treatment of bipolar women (focusing on the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-thyroid axes); and hypotheses to explain the greater prevalence of rapid cycling among bipolar women than among bipolar men. Data clearly indicate that rapid cycling is more common among bipolar women. Data also suggest that bipolar women may have more depressive episodes (and fewer manic episodes) and may be more likely to suffer from mixed (as opposed to pure) mania than bipolar men. While it is clear that bipolar women are at high risk for postpartum episodes, the effects of other reproductive system events (i.e., puberty, menstrual cycle, pregnancy, menopause, use of oral contraceptives or hormone replacement therapy) on the course or treatment of bipolar illness have received little systematic study. It is unclear whether women are at higher risk than men for developing lithium-induced hypothyroidism. Higher rates of hypothyroidism, greater use of antidepressants, and gonadal steroid effects are possible explanations for the greater prevalence of rapid cycling among bipolar women. Gender differences in bipolar illness and the effects of the female reproductive system on the course and treatment of the illness deserve more study. The importance of a longitudinal approach to these questions is emphasized.

Gender Differences in Psychiatry

There are important gender differences in the epidemiology of psychiatric disorders and in the effects of drugs used to treat these disorders. Women are major consumers of psychotropic drugs, but they have often been excluded from drug trials that establish tolerability and dose parameters. Because women have a higher proportion of adipose tissue than men, higher plasma drug concentrations and longer elimination half-lives can occur in women. In this review, gender differences are examined for the most prevalent diagnoses with a tradition of pharmacological responsivity. Anxiety disorders are generally more common in women, although social phobia and post-traumatic stress dis order may have an equal gender distribution. Obsessive-compulsive disorder has a slight preponderance in women, while patients with generalised anxiety disorder and panic disorder are predominantly women. Benzodiazepines that undergo conjugation appear to have a longer elimination time in women, and concomitant administration of oral contraceptives can decrease clearance of these drugs. Women are twice as likely to have a major depression and equally likely to have bipolar disorder as men. However, women are overrepresented in the rapid cycling variant of bipolar disorder. Gender data on antidepressant response are mixed, but women are more vulnerable to lithium-induced hypothyroidism. Men and women have equal risk for schizophrenia, but vary in terms of clinical features such as premorbid functioning, age of onset and outcome. Women tend to require lower dosages of antipsychotics, experience a greater improvement in symptoms when receiving these drugs, but are at a higher risk of developing tardive dyskinesia. The incidence of eating disorders (anorexia nervosa and bulimia nervosa) is higher in females than in males. Future attention to gender differences will improve the diagnosis of, allow for more accurate prognosis of, and promote individually designed interventions for psychiatric disorders.

Gender differences in pharmacokinetics and pharmacodynamics of psychotropic medication.

This review explores the theoretical background for and empirical evidence supporting gender-related differences in pharmacokinetics and pharmacodynamic properties of psychotropic medications. The authors reviewed all English-language articles on this topic that involved original research using human subjects. Limited evidence suggests that young women seem to respond better to and require lower doses of antipsychotic agents and benzodiazepines than young men. The administration of exogenous hormones interacts with medications, changing plasma levels and possibly conferring greater risks for toxicity. Young women may have an enhanced response to nontricyclic antidepressants. Too little basic and clinical research has been conducted on sex differences in therapeutic effects and side effects of psychopharmacological treatments. Addressing these differences as well as similarities will lead to safer and more effective treatment for all patients.

Evaluation of thyroid function in patients with rapid-cycling and non-rapid-cycling bipolar disorder

The problem of whether rapid-cycling (RC) bipolar disorder is more frequently associated than non-rapid-cycling (NRC) bipolar disorders with thyroid dysfunction was investigated in two groups of 11 women matched for age and therapy. Seven patients in each group were under chronic lithium therapy. Both RC and NRC patients, as compared to euthyroid controls, showed a reduction in mean total and free thyroid hormone concentrations, subnormal values of free thyroxine being found in four RC and three NRC patients. No patient had supranormal baseline thyroid stimulating hormone (TSH) values, but an exaggerated TSH response to thyrotropin releasing hormone was found in three RC and two NRC patients: all these patients had been receiving lithium therapy for more than one year. No differences in the prevalence of goiter and thyroid-directed autoantibodies were observed in the two groups. These data confirm that bipolar disorder, especially during treatment with lithium, is associated with at least subclinical hypothyroidism, and suggest that RC patients do not differ from NRC patients in the prevalence of spontaneous or lithium-induced thyroid hypofunction. Lithium-induced hypothyroidism is likely to be related to the length of treatment.

Lithium toxicity and myxedema coma in an elderly woman

The development of hypothyroidism as a side effect of lithium therapy is a well recognized phenomenon. However, the presentation of myxedema coma after lithium intoxication has not been previously documented. In this case lithium toxicity may have exacerbated preexisting hypothyroidism to the point of respiratory arrest. Based on this case, we recommend periodic monitoring of thyroid function in an effort to detect preexisting hypothyroidism or lithium-induced hypothyroidism.