Hyperthyroidism, hypothyroidism

Thyroid dysfunction is a fairly common disorder to be found in clinical practice. The thyroid synthesizes two hormones, triiodothyronine (T ) and thyroxine (T4), dipeptides containing 3 and 4 atoms of iodine respectively in each molecule. The thyroid stimulates cell metabolism of most tissues, might cause hypermetabolism symptoms loss of weight in spite of increased appetite, palpitations, tremor of the fingers, anxiety, heat intolerance. The hormone activity is mainly carried out by T3. Most of it derives by monodeiodination from T4 that is secreted directly by the thyroid. Both hormones in the blood are bound to plasma proteins. In the development of medical applications of microcalorimetry, among the first pathological conditions to be studied were thyroid dysfunctions. 

Studies in different laboratories have shown increased heat production in leukocytes [58,59] from hyperthyroid patients. In the former study [58] heat production was measured with a flow microcalorimeter in the whole leukocyte population In the latter investigation [59] microcalorimetric measurements were carried out in the lymphocyte population using a static ampoule calorimeter. The results showed a qualitative agreement between the two studies, although the two investigations are not comparable since the former 

Heat production rate (P) of erythrocytes and lymphocytes from hyperthyroid patients before and after treatment. The variation of values is dependent of different experimental conditions. 

Source Cell samples Before After Controls 

The action of thyroid hormones at the cellular level is expected to be carried out by attachment of the hormones at the nuclear receptors in the target cells. The increased heat production in erythrocytes, cells without a nucleus, indicates that thyroid hormones have the capability to stimulate cell metabolism also by other mechanisms than through nuclear receptors It is well established that thyroid hormones stimulate oxygen con.sumption, whereas their effect on anaerobic metabolism is unclear. Calorimetric studies on erythrocytes were therefore performed to clarify the influence of thyroid hormones on anaerobic metabolism. After initial calorimetric recording of erythrocyte total metabolism, sodium fluoride was added to the cell suspension to inhibit enolase and thus stop substrate utilization through the anaerobic pathway [62]. The decrease of heat production rate in samples with sodium fluoride corresponds to the anaerobic contribution, whereas the values from samples with sodium fluoride reflect aerobic metabolism. The value from samples without sodium fluoride reflects total cell metabolism. The results of 

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Cushing s disease, hyperparathyroidism, hyperthyroidism, hypothyroidism, hypoglycemia, hyponatremia, hyperkalemia, pheochromocytoma, vitamin B12 or folate deficiencies Neurologic... 

Diet Patients must follow a prescribed diet and exercise regularly. Determine the time, number, and amount of individual doses and distribution of food among the meals of the day. Do not change this regimen unless prescribed otherwise. Hyperthyroidism/Hypothyroidism Hyperthyroidism may cause an increase in the renal clearance of insulin. Therefore, patients may need more insulin to control their diabetes. Hypothyroidism may delay insulin turnover, requiring less insulin to control diabetes. 

Ora/-Adverse reactions requiring discontinuation include Pulmonary infiltrates or fibrosis paroxysmal ventricular tachycardia CHF elevation of liver enzymes visual disturbances solar dermatitis blue discoloration of skin hyperthyroidism hypothyroidism. Adverse reactions occurring in at least 3% of patients include CFIF Gl complaints (nausea, vomiting, constipation, anorexia) dermatologic reactions (photosensitivity, solar dermatitis) neurologic problems (malaise, fatigue, tremor/abnormal involuntary movements, lack of coordination, abnormal gait/ataxia, dizziness, paresthesias) abnormal liver function tests. 

Coexistent primary hyperparathyroidism Other endocrine disorders Hyperthyroidism Hypothyroidism Acromegaly... 

Thyroid conditions simple goiter, hyperthyroidism, hypothyroidism... 

Long-term outcome Eudiyroidism or hyperthyroidism Hypothyroidism... 

Normal Hyperthyroid Hypothyroid Athyreotic (short) Athyreotic (long) Units... 

Figure 73.4 Food supplementation with iodine can produce hyperthyroidism, hypothyroidism, or thyroid autoimmune diseases, in relationship to the previous state of the thyroid gland.

Dose I2 (mg/day) Patients with lab values Hyperthyroidism Hypothyroidism ... 

Cases of hyperthyroidism, hypothyroidism, and iodine-induced thyroid toxicity have been reported in association with excessive use of kelp and kombu (De Smet et al. 1990 Eliason 1998 Ishizuki et al. 1989 Mussig et al. 2006 Salas Coronas et al. 2002 Shilo and Hirsch 1986 Shimizu et al. 2003). 

Imidazole acetic acid > thyrotoxicosis hyperthyroidism hypothyroidism chronic atrophic dermatitis mastitis carcinoma of the mamma carcinoma of the lung myotonic dystrophy normal ... 

Within the thyroid system, disease states can lead to hypothyroidism and hyperthyroidism. Hypothyroidism results from abnormally low production of thyroid hormone in thyroid glands. The prevalence of this condition is reported as being between 2% and 5% of the world population, although a substantial number are in the sub-clinical category. Hypothyroidism is much more common in females than in males, and the frequency of the disease increases with age. The problem may arise due to an insufficient intake of iodine in the diet. It may be due to an inherited disorder (Hashimoto s thyroiditis) or it may be due to inflammation of the thyroid gland (lymphocytic thyroiditis). The conventional treatment for this condition is use of thyroid hormones levothyroxine sodium or liothyronine sodium (Fig. 20.11). 

Iodine. Of the 10—20 mg of iodine in the adult body, 70—80 wt % is in the thyroid gland (see Thyroid and antithyroid preparations). The essentiahty of iodine, present in all tissues, depends solely on utilisation by the thyroid gland to produce thyroxine [51-48-9] and related compounds. Well-known consequences of faulty thyroid function are hypothyroidism, hyperthyroidism, and goiter. Dietary iodine is obtained from eating seafoods and kelp and from using iodized salt. 

Lithium. In the lithium carbonate treatment of certain psychotic states, a low incidence (3.6%) of hypothyroidism and goiter production have been observed as side effects (6,36) (see Psychopharmacologicalagents). It has been proposed that the mechanism of this action is the inhibition of adenyl cyclase. Lithium salts have not found general acceptance in the treatment of hyperthyroidism (see Lithiumand lithium compounds). 

The symptoms of hypothyroidism and hyperthyroidism are given in Table 51-1. A severe form of hyperthyroidism, called thyrotoxicosis or tiiyroid storm, is characterized by high fever, extreme tachycardia, and altered mental status. Thyroid hormones are used to treat hypothyroidism and antithyroid... 

Discuss the prevalence of thyroid disorders, including subclinical (mild) and overt (typical signs and/or symptoms present) hypothyroidism and hyperthyroidism. 

Describe the management of hypothyroidism and hyperthyroidism in pregnant women. 

O In most patients with thyroid hormone disorders, the measurement of a serum thyroid-stimulating hormone (TSH) level is adequate for the diagnosis of hypothyroidism and hyperthyroidism. The target TSH for most patients being treated for thyroid disorders should be the mean normal value of 1.4 milliunits/L or 1.4 microunits/mL (target range 0.5-2.5 milliunits/L or 0.5-2.5 microunits/mL). 

Hyperthyroidism is much less common than hypothyroidism. In NHANES III,1 1.3% of the population was hyperthyroid (0.5% overt, 0.8% subclinical), with the highest incidences in women overall and in men and women in the 20 to 39 and over 80 years of age groups. The Colorado Thyroid Health Study2 showed a hyperthyroid incidence of 2.2% (2.1% subclinical). 

Interferon-a causes hypothyroidism in up to 39% of patients being treated for hepatitis C infection. Patients may develop a transient thyroiditis with hyperthyroidism prior to becoming hypothyroid. The hypothyroidism may be transient as well. Asians and patients with preexisting anti-TPOAbs are more likely to develop interferon-induced hypothyroidism. The mechanism of interferon-induced hypothyroidism is not known. If LT4 replacement is initiated, it should be stopped after 6 months to re-evaluate the need for replacement therapy. 

American Association of Clinical Endocrinologists Thyroid Task Force. Evaluation and Treatment of Hyperthyroidism and Hypothyroidism, 2002 www.aace.com/clin/guidelines/hypo hyper.pdf accessed October 30,2005. 

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