Clinical and metabolic studies in thyroid disease

Hypothyroid Symptoms Fail to Predict Thyroid Insufficiency in Old People: A Population-Based Case-Control Study

BACKGROUND

Clinic-based studies have indicated that older hypothyroid patients may present only few symptoms.

METHODS

In this population-based study of hypothyroidism, we investigated how the power of symptom presence predicts overt hypothyroidism in both young and older subjects. We identified patients newly diagnosed with overt autoimmune hypothyroidism in a population (n = 140, median thyroid-stimulating hormone, 54.5; 95% confidence interval [CI], 28.3-94.8; median total T4, 37; 95% CI, 18-52) and individually matched each patient with 4 controls free of thyroid disease (n = 560). Participants filled out questionnaires concerning the presence and duration of symptoms. We compared the usefulness of hypothyroidism-associated symptoms in predicting overt hypothyroidism in different age groups (young: <50 years, middle age: 50-59 years, old: ≥60 years) also taking various confounders into account.

RESULTS

In young hypothyroid patients, all 13 hypothyroidism-associated symptoms studied were more prevalent than in their matched controls, whereas only 3 of those (tiredness, shortness of breath, and wheezing) were more prevalent in old patients. The mean numbers of symptoms presented at disease onset were 6.2, 5.0, and 3.6 at the ages of 0 to 49 years, 50 to 59 years, and 60+ years, respectively. In young versus old people with 0 to 1 symptoms, the odds ratio for being hypothyroid was 0.04 (95% CI, 0.007-0.18) versus 0.34 (95% CI, 0.15-0.78) (reference all other groups). In young versus old subjects reporting ≥4 symptoms, the odds ratio for being hypothyroid was 16.4 (95% CI, 6.96-40.0) versus 2.22 (95% CI, 1.001-4.90). Receiver operating characteristic analyses revealed that the symptom score was an excellent tool for predicting hypothyroidism in young men (area under the receiver operating characteristic curve, 0.91; 95% CI, 0.82-0.998), whereas it was poor in evaluating older women (area under the receiver operating characteristic curve, 0.64; 95% CI, 0.54-0.75).

CONCLUSION

Hypothyroid symptom score is a good discriminating tool to identify hypothyroidism in young patients but fails to identify hypothyroidism in the elderly. Thus, thyroid function should be tested on wide indications in old age.

Gender differences in symptoms of hypothyroidism: a population-based DanThyr study

OBJECTIVES

We examined the gender-specific symptom prevalences in hypothyroidism and in healthy controls and explored the extent to which symptoms indicative of thyroid status may be different in women and men.

DESIGN AND METHODS

Patients newly diagnosed with overt autoimmune hypothyroidism (n = 140) and controls free of thyroid disease (n = 560) recruited from the same population participated in a population-based study of The Danish Investigation of Iodine Intake and Thyroid Diseases (DanThyr). Participants underwent a comprehensive programme including blood tests and completion of questionnaires. The gender-specific distribution of 13 hypothyroidism-associated symptoms and a simple combined score (0-13) was explored in conditional uni- and multivariate models taking into account a broad spectrum of possible confounders. Diagnostic odds ratios (DORs) were calculated as measures for the association between participant status (case vs control) and presence of symptoms (yes vs no).

RESULTS

In overt autoimmune hypothyroidism, 94·9% of women and 91·3% of men (P = 0·62) reported at least one of the hypothyroidism-associated symptoms, with tiredness as the most common symptom followed by dry skin and shortness of breath. In contrast, women free of thyroid disease self-reported at least one hypothyroidism-associated symptom considerably more often than men (73·7% vs 51·1%, P < 0·001). DORs (±SEM) for 0-1/2-3/4-13 symptoms were 0·07 (0·04-0·10)/2·15 (1·57-2·94)/7·99 (6·15-10·4) in men and 0·21 (0·16-0·28)/0·62 (0·58-0·66)/1·99 (1·90-2·09) in women.

CONCLUSION

The presence of symptoms is more indicative for overt autoimmune hypothyroidism in men than in women, and presumably persistent symptoms after therapy of hypothyroidism will be more common in women.

Hypothyroid symptoms and the likelihood of overt thyroid failure: a population-based case-control study

BACKGROUND

It is generally accepted that patients suffering from hypothyroidism may express few symptoms, but this has not been studied in a population-based study design.

OBJECTIVES

To study the array of symptoms as they are reported in newly diagnosed overt autoimmune hypothyroidism using a population-based case-control design.

METHODS

Patients with new overt autoimmune hypothyroidism (n=140) and their individually matched thyroid disease-free controls (n=560) recruited from the same population underwent a comprehensive program and self-reported a number of symptoms. We identified the symptoms associated with overt hypothyroidism and calculated positive (LR+) and negative (LR-) likelihood ratios as well as diagnostic odds ratios (DORs) as measures for the association between disease state and symptoms.

RESULTS

Among 34 symptoms investigated, 13 symptoms were statistically overrepresented in hypothyroidism. Hypothyroid patients suffered mostly from tiredness (81%), dry skin (63%), and shortness of breath (51%). Highest DORs (95% CI) were reported for tiredness (5.94 (3.70-9.60)), hair loss (4.58 (2.80-7.51)), and dry skin (4.09 (2.73-6.16)). A hypothyroidism-component-score was defined as the number of hypothyroidism-associated symptoms (range: 0-13). LR+ for participants with a hypothyroidism-component-score of 0 was 0.21 (0.09-0.39), meaning that the post-test probability was lowered to 21% of what it was before asking for symptoms. LR+ for scores of 1-2/3/4-6/7-9/10-13 were: 0.47 (0.30-0.72)/1.16 (0.70-1.87)/1.90 (1.29-2.45)/3.52 (2.30-5.36)/6.29 (2.30-17.7).

CONCLUSIONS

None of the individual symptoms of hypothyroidism had high LRs or DORs. Thus, neither the presence nor absence of any individual hypothyroidism symptom was reliable in the decision making of who should have their thyroid function tested. Therefore, even minor suspicion should lead to a blood test.

Negative association between free triiodothyronine level and international normalized ratio in euthyroid subjects with acute myocardial infarction

AIM

To investigate the relationship between free triiodothyronine (FT3) and the international normalized ratio (the ratio of the prothrombin time of a patient to the normal sample, INR) in Chinese euthyroid subjects with acute ST-segment elevation myocardial infarction (STEMI).

METHODS

A total of 231 consecutive patients (177 males, 54 females) with STEMI were enrolled. Anthropometric and laboratory measurements, including heart rate, respiratory rate, blood pressure, body temperature, platelet count, INR, prothrombin time, activated partial thromboplastin time, FT3, free thyroxine (FT4), and thyroid-stimulating hormone, were collected from all the patients. The levels of FT3 and FT4 were measured with a full-automatic immune analyzer. The INR was determined using a coagulation analyzer.

RESULTS

Patients were classified into 4 groups according to their quartile FT3 and FT4 levels: 0.40-3.09 (n=52), 3.10-3.69 (n=56), 3.70-4.29 (n=64) and 4.30-7.10 (n=59) for FT3; 4.9-14.8 (n=57), 14.9-16.8 (n=58), 16.9-18.7 (n=57) and 18.8-29.0 (n=59) for FT4. Subjects with a high FT3 level had significantly lower values of INR than those with a low FT3 level (P=0.01). Multiple linear regression analysis revealed decreased serum FT3 as an independent risk factor for elevated INR values (β=-0.139, P=0.025). The value of INR was similar among the 4 groups according to the quartile FT4 levels (P=0.36).

CONCLUSION

Free triiodothyronine was negatively associated with INR in the patients with acute STEMI and normal thyroid function.

The interpretation of the serum protein-bound iodine: A review

The effects of physiological and environmental factors, of thyroid and non-thyroid diseases, and of drugs on the serum protein-bound iodine are described and discussed.

Cutaneous manifestations of endocrine disorders: a guide for dermatologists

Dermatologists may commonly see skin lesions that reflect an underlying endocrine disorder. Identifying the endocrinopathy is very important, so that patients can receive corrective rather than symptomatic treatment. Skin diseases with underlying endocrine pathology include: thyrotoxicosis; hypothyroidism; Cushing syndrome; Addison disease; acromegaly; hyperandrogenism; hypopituitarism; primary hyperparathyroidism; hypoparathyroidism; pseudohypoparathyroidism and manifestations of diabetes mellitus. Thyrotoxicosis may lead to multiple cutaneous manifestations, including hair loss, pretibial myxedema, onycholysis and acropachy. In patients with hypothyroidism, there is hair loss, the skin is cold and pale, with myxedematous changes, mainly in the hands and in the periorbital region. The striking features of Cushing syndrome are centripetal obesity, moon facies, buffalo hump, supraclavicular fat pads, and abdominal striae. In Addison disease, the skin is hyperpigmented, mostly on the face, neck and back of the hands. Virtually all patients with acromegaly have acral and soft tissue overgrowth, with characteristic findings, like macrognathia and enlarged hands and feet. The skin is thickened, and facial features are coarser. Conditions leading to hyperandrogenism in females present as acne, hirsutism and signs of virilization (temporal balding, clitoromegaly).A prominent feature of hypopituitarism is a pallor of the skin with a yellowish tinge. The skin is also thinner, resulting in fine wrinkling around the eyes and mouth, making the patient look older. Primary hyperparathyroidism is rarely associated with pruritus and chronic urticaria. In hypoparathyroidism, the skin is dry, scaly and puffy. Nails become brittle and hair is coarse and sparse. Pseudohypoparathyroidism may have a special somatic phenotype known as Albright osteodystrophy. This consists of short stature, short neck, brachydactyly and subcutaneous calcifications. Some of the cutaneous manifestations of diabetes mellitus include necrobiosis lipoidica diabeticorum, diabetic dermopathy, scleredema adultorum and acanthosis nigricans.

Prevalence of paradoxically normal serum cholestrol in morbidly obese women

The paradox that cholesterol may be lower in extremely obese subjects versus those who are less overweight, although originally observed more than 40 years ago, has never been documented in a systematic fashion. We have therefore prospectively determined the body mass index (BMI) and serum cholesterol concentration in 3,312 women. The percentage of women with serum cholesterol in the normal range (<200 mg/dL) decreased with an increasing BMI, from 55% in women with a BMI less than 20 kg/m2 to 28% in those with a BMI of 30 to 35 kg/m2. Serum cholesterol greater than 300 mg/dL was found in only 2% of individuals with a BMI less than 20 kg/m2 but in 6% of the group with a BMI between 30 and 35 kg/m2. However, among morbidly obese women (BMI >40 kg/m2, n = 46), 39% presented with serum cholesterol less than 200 mg/dL and only one woman had serum cholesterol more than 300 mg/dL. With the BMI, the fitted regression model shows an increase in cholesterol for low BMIs, while cholesterol appears to decrease with larger values for the BMI. The age-dependent increase in cholesterol is more evident in younger women versus older women, where it tends to disappear. It is concluded that among morbidly obese women (BMI >40 kg/m2), there is a substantial subgroup with normal serum cholesterol.

Diagnostic tests for thyroid antibodies: a comparison of the precipitin and latex-fixation (Hyland TAI) tests

The clinical significance of thyroid antibodies is discussed and it is concluded that, of the antibody tests which have been extensively applied, the precipitin test is the most useful for diagnostic purposes. The recently introduced Hyland TA test is compared with the precipitin test. The TA test gives a rapid result and is slightly more sensitive, but it remains undecided whether a true positive result is always indicative of clinically important degrees of chronic thyroiditis. The TA test also gives occasional false positive results, not indicative of antibody to thyroglobulin. Furthermore, approximately 12% of precipitin-positive sera from patients with Hashimoto's disease give negative TA tests, and since these also have low titres, or are negative, in the tanned red cell haemagglutination test, the precipitin test is the only simple method of demonstrating the antibody concerned. In spite of these disadvantages, the TA test is regarded as a useful procedure, and there are advantages in using both the precipitin and TA tests together for routine diagnostic purposes. A modification is described whereby the TA test reagent may be used to titrate antibody to thyroglobulin.

OpenLabs services for ordering laboratory investigations

An automated system is described that screens requests for laboratory investigations from GPs and delivers feedback with respect to the adequacy of the requests. The system has to replace and extend the current system in which feedback is provided on a manual basis each half year, based on the tests requested during a period of one month, randomly selected from the previous half year. It has been reported elsewhere that the manual system reduced the number of tests requested considerably. The criteria used by the automated system and the manual system are based on guidelines and work agreements that GPs have agreed to follow when requesting investigations. It is concluded that the automated system is very user-friendly and that in the order of 4-17% of the requested tests could be identified as unnecessary, with a false negative rate in between 4% (for hyperthyroidism) and 23% (for hypothyroidism). The achieved reduction in the number of tests is in addition to the reduction obtained in the manual system.

Evaluation of GPs' medical knowledge by a decision support system

This paper deals with the EValuator which is a multipurpose DSS. EV can be applied by creators of automated disease and therapy models to get insight into knowledge necessary for diagnosis and treatment of diseases. GPs, trainees/interns, hospital clinicians, and students can test their medical knowledge with EV. If necessary, EV offers decision support. In a functionality test, EV was used by GPs to assess their knowledge of thyroid disorders. Test conclusions referred to the GPs' level of medical knowledge of thyroid disorders, differences in EV usage by urban and rural GPs, use of thyroid disorder indices and the GPs' commendations that EV is capable of providing automated decision support to medical professionals in daily practice, and that it can very well be used in the education of students and in GP refresher courses.

Primary haemostasis in thyroid disease

OBJECTIVES

There have been reports on a bleeding tendency in hypothyroidism resembling von Willebrand's disease. The aim of the present study was to investigate whether altered primary haemostasis is a general phenomenon in thyroid disease.

DESIGN/SETTING

A total of 10 patients with hyperthyroidism and nine patients with hypothyroidism were studied at diagnosis, and during treatment with carbimazole or L-thyroxine, respectively, when euthyroidism had been achieved.

RESULTS

In untreated hypothyroidism, template bleeding time was prolonged (median 9.3 min, range 3.8-20.0 min) compared to that in controls (median 4.0 min, range 3.0-6.0 min; P < 0.05), whereas maximal agglutination velocity induced by ristocetin was decreased (38% min-1, range 4-52% min-1 vs. 70% min-1, range 60-81% min-1, P < 0.05). The level of von Willebrand factor antigen in plasma from hypothyroid patients was less than half of the value in hyperthyroid patients. This difference disappeared after euthyroidism was achieved.

CONCLUSIONS

We found that changed primary haemostasis is a general feature of hypothyroidism, and that it is resolved after levothyroxine treatment.

Clinical presentation of spontaneous primary hypothyroidism in adults

In a retrospective study of 309 cases of hypothyroidism seen at King Fahd Hospital of the University (KFHU), Al-Khobar, 124 (90 Saudis and 34 non-Saudis) adult patients with spontaneous primary hypothyroidism satisfied the inclusion criteria for detailed analysis. Their male:female ratios for Saudis and non-Saudis were 1:4.6 and 1:3.9 respectively. The majority were diagnosed in their third and fourth decades. The prevalence of previously undiagnosed spontaneous and biochemically overt primary hypothyroidism in Saudis was 5.2/1000 females and 0.94/1000 males. FT4I was normal in 43 (35%) and low in 81 (65%). FT4I correlated with cold intolerance, constipation, dry skin, hoarseness, delayed reflex relaxation, and coarse and cold skin. In rank order, presenting symptoms in those with low FT4I were tiredness (56%), cold intolerance (38%), constipation, weight gain, menstrual disturbance - especially amenorrhea - (36% each), dry skin (35%), hoarseness (31%); signs were coarse skin (53%), delayed reflex relaxation (32%), cold skin and goiter (24% each). The above clinical findings may help physicians in the early detection of primary hypothyroidism. Population-based studies are necessary to provide more data on this disease in this country.

Factors influencing the transferability of medical decision support systems

Transferability is a key issue in the development and implementation of medical decision support systems. Such systems have up to now tended to be confined to the development site. Transferability represents the integrated effect of several more basic attributes of Decision Support Systems. These attributes can be considered to belong to two main groups: those concerned with the Medical Domain (of the system) and those concerned with the Information Technology by which the System functions. Among the Domain issues the most important are: Epidemiology, Terminology and Methodology. Concerning the Information Technology issues the most important are: Knowledge Acquisition and Representation methods, Database design and integration with inference mechanism. The effect of each of the individual factors is considered by illustrations from the literature and by studying the results of recent experiments where databases and decision support systems from different countries are interchanged. This exercise allows some planning in the design of future systems with the aim of improving overall transferability and therefore applicability.

Vitamin A deficiency and connective tissues: a new etiological approach

A unifying concept, that the impairment of connectives tissue, owing to the effect of immigrant cells, is at the basis of the pathogenesis of Vitamin A deficiency has been considered. Changes in various tissues and organs have been reviewed in the light of the recent discoveries in the field of histology (1). An effort has been made to link the various symptoms of Vitamin A deficiency to those related to other pathologies where connective tissues are involved, and to suggest a plan for research to be undertaken to achieve a better knowledge of the etiology of Vitamin A deficiency.

Clinical and laboratory evaluation of four methods of assessing free thyroxine status in thyroid clinic patients

The clinical value of four laboratory methods of assessing free thyroxine status was compared in 82 consecutive patients newly referred to a thyroid clinic with suspected thyroid dysfunction. The methods of determining free thyroxine used were: (1) free thyroxine index using a thyroid hormone uptake test (FTI (THUT)); (2) a free thyroxine index using thyroxine binding globulin (FTI (TBG)); (3) a kinetic radioimmunoassay (Immophase); and (4) an equilibrium dialysis method. The definitive thyroid status was evaluated by a combination of clinical assessment (including Wayne index), routine tests of thyroid function (total T4, T3, TSH, and TRH tests where appropriate), and by therapeutic trial in one case. The diagnostic efficiency of the tests was markedly dependent upon the method of determining the reference range for euthyroid patients. Best efficiency for each test was achieved using an amended range after excluding outliners. Test efficiency was then 97.6% for FTI (THUT) and the kinetic RIA and 96.8% for FTI (TBG). Misclassification by one or more of these tests occurred in only four patients (mild hypothyroid, euthyroid on phenytoin, euthyroid on oral contraceptive and valium, T3 hyperthyroid). In contrast, free T4 by equilibrium dialysis was much less efficient (86.6%) and was technically the most complex. Overall the kinetic T4 RIA provided similar diagnostic information to the indirect indices. However, further studies of cost benefit in settings other than a thyroid clinic are required to assess whether this method might replace total T4 and/or FTI as a first-line test of thyroid function.

Use of a computer-based postal questionnaire for the detection of hypothyroidism following radioiodine therapy for thyrotoxicosis

A computer-processed postal questionnaire was devised to detect hypothyroidism in patients treated previously for thyrotoxicosis with radioiodine. In a study of 232 patients treated with 131I at the Royal Melbourne Hospital between four and ten years previously, the sum of symptomatic answers in the questionnaire was a sensitive discriminator of hypothyroidism, and allowed 80% of euthyroid patients to be excluded from further assessment. Questions concerned with general well-being and energy, voice and skin changes, showed the highest sensitivity and specificity. The combination of these questions alone was an effective means of identifying hypothyroidism, with a sensitivity and specificity comparable to the more sophisticated technique of discriminant function analysis. Hypothyroidism had an incidence of between 20% and 35% six to eight years after 131I therapy and was related to a smaller initial goitre size for a given dose of 131I. This postal questionnaire, in conjunction with a computer-based automatic recall system, promises to be an efficient and reliable screening tool for the detection of hypothyroidism in the increasing number of patients "at risk" following 131I therapy.

Systolic time intervals in thyroid disease

The systolic time intervals; total electro-mechanical systole (QS2), left ventricular ejection time (LVET), pre-ejection period (PEP), and ratio of PEP/LVET were measured from external readings in twenty hyperthyroid and fifteen hypothyroid patients. The hyperthyroid subjects showed shortening of the PEP and reduction in the PEP/LVET. The hypothyroid group showed lengthening of the PEP, shortening of the LVET and increased PEP/LVET. These changes returned towards normal in ten patients rendered euthyroid with appropriate therapy. The value of these measurements to predict the thyroid status was examined in a mixed group of seventy-four patients. There was close agreement between diagnosis predicted from systolic time intervals and that made independently from clinical and biochemical assessment, suggesting that the systolic time intervals may have been a useful place in the clinical assessment of thyroid patients.

The adhesiveness of human blood platelets and thyroid function

Hypothyroidism is associated with severe coronary atherosclerosis. In spite of this the reported incidence of angina pectoris and myocardial infarction in untreated hypothyroidism is small. Since many authors consider the formation of a thrombus in coronary arteries to be the final event of the process which leads to myocardial infarction, changes in the platelet function may explain the paradoxical rarity of myocardial infarction in untreated hypothyroidism. To evaluate this hypothesis, platelet adhesiveness has been estimated before and after treatment in 9 hypothyroid and 16 thyrotoxic patients. In thyrotoxicosis the platelet adhesiveness was significantly increased, but decreased to normal after treatment. In hypothyroidism platelet adhesiveness was abnormally low but increased to normal value after thyroid hormone replacement. This may be an important factor in precipitating myocardial infarction in patients with hypothyroidism and coronary artery atherosclerosis.

The diagnosis of thyrotoxicosis

Thyrotoxicosis is a clinical syndrome due to excessive amounts of thyroid hormone in the circulation and tissues. Graves' disease, goitre and exophthalmos, is the commonest variety, but in some parts of the world thyrotoxicosis supervenes on the background of a long standing nodular goitre. Other varieties such as ectopic TSH syndromes are very rare.

The diagnostic sequence in practice starts with clinical suspicion and a decision can often be made on the symptoms and signs alone. It is, however, always advisable to confirm the presence or absence of thyrotoxicosis. There has been re-orientation in the simple test procedure used in this respect. Measurements such as serum TSH and serum TSH response to TRH and measurements of serum LATS levels are available only in a few centres and are not discussed in detail.

Tests based on the carriage of thyroid hormones in the blood are preferable to in vivo radionuclide studies, particularly when the patient is thought to be euthyroid. We advise a serum PB¹²⁷I and serum total thyroxine estimation in all patients. If the data are abnormal we add a serum T3 resin estimation to check whether the values are due, for example, to iodine contamination or altered binding.

We advise radionuclide studies in all doubtful cases and measurements such as the 4 hr or 24 hr ¹³¹I uptake and the 48 hr serum PB¹³¹I are very helpful. A thyroid uptake suppression test may be required if there is still doubt. In general those patients going for thyroidectomy or ¹³¹I therapy should have a scan performed. With improved technology much safer radionuclides, such as ¹²³I or ^99mTc, may be usable when thyrotoxicosis is suspected in children or during pregnancy.

Gel scintillation counting of I-131 in plasma at high efficiencies

A method is described for assaying low concentrations of (131)I in plasma by detecting the beta radiation in a gel scintillator. Higher detection efficiencies are obtained compared with measurements of the gamma radiation from this radioisotope using a well-type crystal of sodium iodide.