Hypothyroidism definition

One definition of post-operative paralytic ileus is the failure of the patient to pass faeces or flatus within 60 hr. of the termination of a surgical abdominal operation . A somewhat similar condition may arise in cases of gross mechanical obstruction of the gut. It is well known also that operations involving handling of the gut or the peritoneum are especially liable to cause paralytic ileus. Peritonitis and post-operative pain, inadequately treated with morphia, also precipitate paralytic ileus. Pneumonia, meningitis and typhoid predispose to paralytic ileus, whilst severe hypothyroidism can also be complicated by a paralytic ileus. 

Despite these clues, a definitive diagnosis often cannot be made. In that case, a prudent course is to treat what would be treatable. The initial evaluation should carefully look for treatable medical causes of dementia or depression. These include vitamin deficiency and hypothyroidism among others. If no medical causes are found, then treatment for depression should be started. If the patient is depressed and suffering from a pseudodementia, the patient can expect full recovery of memory as the depression resolves. But if the patient has a progressive dementia such as Alzheimer s disease, then treatment for depression has done no harm and may still provide some benefit. 

Behavioral disorders, including hyperactivity and impaited concentration, are known to be associated with hyperthyroidism and hypothyroidism, respectively. This evidence validated the hypothesis that ADHD might be similarly related to thyroid disease. Nonetheless, the vast majority of the studies carried out to address this issue failed to demonstrate a definite association between ADHD and thyroid function abnormalities, and therefore the effective role of thyroid hormones in the pathogenesis of the disorder became a candidate for reassessment. It must be pointed out however, that most of these studies evaluated thyroid function in schoolchildren or adults, without taking into account any previous thyroid dysfunction suffered either by them or their mothers during gestation. 

Previous total or subtotal thyroidectomy for nodular goiter and the presence of an increase in serum TSH level indicate the diagnosis of post-operative hypothyroidism. Loss of thyroid function may also occur after definitive therapy for previous thyrotoxicosis, either with radioiodine or thyroidectomy. Some patients may exhibit a transient phase of thyroid hypofunction after partial thyroidectomy or radioiodine therapy with recovery of function. Other causes of hypothyroidism, such as thyroid dysgenesis, infiltrative diseases, iodine deficiency, iodine excess, painless thyroiditis and subacute thyroiditis are less common in the elderly and are usually easily recognizable by their clinical and analytical features. 

There is definitely an overlap in responses obtained in normd subjects and those obtained in patients with partial thyroid deficiency, even if the number of injections of TSH is reduced. However, failure of the thyroid uptake and total T4 to increase after TSH is strong evidence of primary thyroid disease. In the patients receiving thyroid hormone therapy, a significant response to TSH fairly conclusively excludes underlying thyroid failure unless the patient has been taking this therapy in full doses for many years. The test is probably most useful in distinguishing idiopathic thyroid failure from secondary or pituitary hypothyroidism. 

A single estimation of serum TSH which is so convenient, has replaced the TSH stimulation test which was inconvenient and sometimes dangerous for the patient. A definitely elevated level of serum TSH, e.g., in excess of 30 /xU/ml, is very convincing evidence of impairment of thyroid reserve (H4, 18). A finding of a normal TSH with a definitely lowered FTI and T3 concentration in the serum, in a clinically hypothyroid patient, is good evidence for pituitary disease. Also see Sections 4.1.1 or 4.1.2 for further discussion on the usefulness of the TSH assay. 

It is now becoming increasingly recognized that Ts hypersecreting states other than Ta-thyrotoxicosis exist and can occur in a variety of clinical situations. The common denominator is a slowly decreasing thyroid reserve, which is compensated for, either fully or in part, by a Ts hypersecretion, which is probably TSH mediated. The total T4 levels are either low normal or definitely subnormal, and yet none of these patients show any marked evidence of clinical hypothyroidism. 

So far no definite therapeutic applications have been described for TRH. It has been suggested that it has antidepressant effects, but further controlled studies (M15) did not substantiate the initial reports. The role of TRH as a tool in the treatment of thyroid carcinoma (by increasing uptake of the therapeutic dose of radioiodine by the tumor) (F4) is as yet not confirmed. TRH could be used in the treatment of hypothalamic (tertiary) hypothyroidism, but it does not offer any advantage over thyroid hormone replacement. We have not observed any beneficial effect of TRH in regenerating thyroid remnants after surgery. It has been reported that TRH administration to cows results in an elevation of PRL which increases milk production (K3). Further controlled studies of the applications of TRH in the dairy industry are required. 

Thus the Type I 5 deiodinase activity in cerebral cortex, like that in the liver, requires an active sulfhydryl group, the carboxymethylation of which causes enzyme inactivation. In hypothyroid animals, most of the rT3 is deiodinated by the Type II pathway, since the Type I activity is reduced, and Type II activity increased several fold. Further studies with brain and brown adipose tissue microsomes have shown that the sensitivity of Type II activity to PTU is inversely related to the DTT concentration used during the assay, so that it is important to keep this factor in mind when assessing the sensitivity of a particular enzymatic activity to inhibition by this agent (15,16). Interested readers are referred to these references for a more thorough discussion of this complex area. While the two 5 deiodinase activities are quite distinct enzymatically, until such time as the protein sequences are determined, a definitive answer as to their structural similarities cannot be given. 

The first 3 cases (serial nos 604, 638, 515) in the table had hormonal profiles entirely consistent with severe hypothyroidism although these women did not exhibit the clinical features of hypothyroidism In all three cases the pregnancy outcome was a stillblrth/early neonatal death In the succeeding 3 cases (serial nos 568, 245, 430) the maternal total and free thyroxine values were low but triiodothyronine values were within the normal range In one of these the outcome was a stillbirth/early neonatal death and one child has a hearing/speech defect but no other abnormality and, by our definition, cannot be labelled as an endemic cretin ... 

The investigation of children with thyroglossal cysts shows a definite useful clinical application of the fluorescent technique using either a scanner or a stationary system. These cysts may be confused with ectopic thyroids and misdiagnosis may lead to excision of the patient s only thyroid tissue and result in hypothyroidism. It is thus essential to establish that a normal thyroid is present before excising a suspected thyroglossal cyst. A radionuclide scan is usually advised but a fluorescent study either with a scanner or more simply with a... 

Evidence has been published suggesting that the progressively decreasing intrathyroidal stores parallel and probably condition the incidious development of hypothyroidism in atrophic autoimmune thyroiditis (17, 18). XRF measurements have been helpful in our hands (11) when the results were found to be low, to stimulate more thorough investigations than would have been felt otherwise necessary to come to a definite diagnosis and also to decide whether or not substitution should be started,. 

The most dramatic picture of neonatal hypothyroidism due to severe iodine deficiency has been observed in the Ubangi area in Zaire. In this area, the iodine intake is only 15 jLig/day, the prevalence of endemic goiter and cretinism are 76 % and 5 % of the total population respectively. In such extreme conditions, thyroid function in adults is definitely impaired with the classical picture of low serum concentration of T4 and elevated serum TSH andT3 2... 

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