Thyroid hormones abnormalities

Mooney, C. T., R. E. Shiel, and R. M. Dixon. 2008. Thyroid hormone abnormalities and outcome in dogs with non-thyroidal illness. Journal of Small Animal Practice 49 11-16. 

Thyroid function tests abnormal thyroid hormone levels may suggest hypo- or hyperthyroidism, either of which may be associated with constipation. 

In individuals who took thyroid hormones, 80% of the weight lost was lean body mass (muscle and bone) rather than excess fat. People taking these extracts experienced muscle weakness and bone breakdown, which led to a condition called osteoporosis, in which bones are weakened and the risk of bone fractures or breaks is increased. Thyroid hormone extracts also made the heart work harder by increasing metabolism, which led to problems such as increased heart rate, palpitations, and irregular heartbeat. These problems were potentially life threatening When the heart beats abnormally (or not at all), it is unable to pump blood and oxygen to the brain and body. Individuals die suddenly from this condition because the brain can only function for a few minutes without oxygen and nutrients. 

The treatment goals for hypothyroidism are to normalize thyroid hormone concentrations in tissue, provide symptomatic relief, prevent neurologic deficits in newborns and children, and reverse the biochemical abnormalities of hypothyroidism. 

Thyroid hormone also plays a major role in the maturation of bone. A deficiency of thyroid hormone in early life leads to both delay in and abnormal development of epiphyseal centers of ossification (epiphyseal dysgenesis). Hypothyroidism-induced impairment of linear growth can lead to dwarfism in which the Umbs are disproportionately short in relation to the trunk with the apparent bone age retarded in relation to chronological age. 

Thyroid dysregulation has also been reported in depressed patients. Up to 25% of depressed patients are reported to have abnormal thyroid function. These include a blunting of response of thyrotropin to thyrotropin-releasing hormone, and elevations in circulating thyroxine during depressed states. Clinical hypothyroidism often presents with depressive symptoms, which resolve with thyroid hormone supplementation. Thyroid hormones are also commonly used in... 

Thyroid hormones are not effective and can be detrimental in the management of obesity, abnormal vaginal bleeding, or depression if thyroid hormone levels are normal. Anecdotal reports of a beneficial effect of T3 administered with antidepressants were not confirmed in a controlled study. 

Byme JJ, Carbone JP, Hanson EA. 1987. Hypothyroidism and abnormalities in the kinetics of thyroid hormone metabolism in rats treated chronically with polychlorinated biphenyl and polybrominated biphenyl. Endocrinology 21 520-527. 

Since thyroid illness is commonly associated with depression, especially in women, it has long been observed that treating the thyroid abnormalities also can reverse the depression. This is especially true for treating hypothyroidism with thyroid hormone replacement (either T3 or T4). It has even been observed that giving supplemental thyroid hormone to depressed patients unresponsive to first-line antidepressants but without overt hypothyroidism can boost the antidepressant response of the first-line antidepressant (thyroid combo in Fig. 7—30). Thyroid hormone is also commonly administered to bipolar patients resistant to mood stabilizers, particularly those with rapid cycling (see discussion of combinations for bipolar disorders below). 

Thyroid function tests are often altered by somatropin because of increased conversion of T4 to T3, but this is clinically insignificant at low doses (SEDA-21, 453). One child with Prader-Willi syndrome had a fall in serum thyroxine concentration during somatropin therapy and needed thyroxine replacement (33). Hypothyroidism developed in 11 of 46 growth hormone-deficient children treated with somatropin (34). Prior abnormalities in hypothalamic-pituitary function and alterations in thyroid hormone metabolism, probably both, contributed to the high incidence of hypothyroidism, which was similar to that in previous studies. 

Thyrotoxicosis Abnormally high production of thyroid hormones resulting in symptoms such as nervousness, weight loss, and tachycardia (SYN hyperthyroidism). 

The low T3 syndrome is induced by a decrease in the production of plasma T3 as well as the clearance of plasma rT3 and is observed in several clinical situations such as starvation, systemic illness and the use of certain drugs [115]. In fasting [70] and illness [108] the abnormal thyroid hormone metabolism appears to result from a defective liver uptake and, therefore, a decreased supply of T4 and rT3 for intracellular deiodination. In other conditions such as treatment with PTU or propranolol [116], the defect appears localized in the type I deiodinase itself leading to a decline in T3 formation and rT3 breakdown. 

Third, many physical disorders also affect mental attitudes and behavior. Hyperthyroidism as well as overdoses of thyroid hormone can increase anxiety, irritability, and other emotions that the individual would not ordinarily experience and that can lead to behavioral abnormalities. There are, of course, many similar examples involving hormones such as testosterone and cortisone. More to the point, accidental brain injury to the frontal lobes and surgical lobotomy usually impair judgment, ethical restraint, and self-reflection. The character of the injured individual is often viewed as changed and worsened. 

No abnormalities were found in Brian s urine and his blood cell count was normal. However, his blood glucose was 8.1 mmol l-1 (normal value 3.5-6.7 mmol l-1) and a glucose tolerance test later indicated impaired glucose tolerance. Tests for plasma insulin and thyroid hormones (T3, T4 and TSH) showed normal levels. Two further tests were then performed. A 24-hour urine sample was collected and Brian s free cortisol excretion was found to be considerably higher than normal. A second test, the dexamethasone suppression test, was also carried out. In this test, the patient is given a dose of dexamethasone at 11 -12 p.m. and plasma cortisol is measured early next morning. 

THYROID HORMONES BRONCHODILATORS- THEOPHYLLINE Altered theophylline levels (T or f) when thyroid status was altered therapeutically Uncertain Monitor theophylline levels closely during changes in treatment of abnormal thyroid function. Watch for early features of theophylline toxicity... 

In addidon to abnormalities in the cordsol system, abnormal funcdon of grow th hormone and of thyroid hormone and of their regulatory mechanisms has been reported. Again, these findings are not specific to depression (Schatzberg et al., 2002). 

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