Thyroid Hormones and Antithyroid Drugs

Thyroid hormone abnormalities and outcome in dogs with non‐thyroidal illness

“…The effect of thyroid suppressive medication on circulating total and free T 4 concentrations largely supports the findings of previous studies (Woltz and others 1983, Torres and others 1991, Panciera and Post 1992, Daminet and others 1999, Gaskill and others 1999, Kantrowitz and others 1999, Daminet and Ferguson 2003, Panciera and others 2006). However, there was no significant effect of these drugs on total T 3 or cTSH concentrations which is in contrast to previous reports (Rosychuk 1982, Woltz and others 1983, Daminet and Ferguson 2003). This may reflect variation in drug type, dose and duration of therapy which were not evaluated in the present study.…”

Hypothyroidism in the dog: a retrospective study of sixteen cases

“…A comparative study indicated no significant differences in the T, concentrations determined by the two techniques (Lorenz & Stiff, 1980). The basal T, concentration in euthyroid dogs has been reported variously as 18-3-74-5 nmol/l (Kallfelz, 1977), 12.9-5 1-6 nmol/l (Chastain, 1982;Rosychuk, 1982), 24.0-26.0 nmol/l (Gosselin et al., ), 18.1-60.6 nmol/l (Kraft, 1976 and at least 19.3 nmol/l (Nesbitt et al, 1980). The base-line concentration is variable because, irrespective of thyroid status, T, is changed by certain physiological states as well as a variety of pharmacological agents.…”

“…Pituitary deficiencies have been associated with malformation of the craniopharyngeal duct (Rathke's cleft) (Allan et al, 1978;Scott et al, 1978) and neoplasia (Chastain, Riedesel & Graham, 1979;Allison, Watson & Church, 1983). Since TSH acts only as a stimulant and is not essential for thyroid hormone secretion (Bush, 1969a), the clinical signs are usually less severe in case of pituitary insufficiency (Rosychuk, 1982). Secondary hypothyroidism due to pituitary tumours were associated with other hormonal disturbances (hyperadrenocorticism, diabetes insipidus, hypogonadism) and neurological abnormalities (Chastain, Riedesel & Graham, 1979;Allison, Watson & Church, 1983) and the condition of the patients worsened progressively.…”

“…Few cases of congenital hypothyroidism are documented in the dog (Bush, 1969b;Schawalder, 1980;Chastain et al, 1983). More common is acquired hypothyroidism, of which three forms are recognized (Bush, 1969a;Rosychuk, 1982): primary (reduced mass of functioning thyroid tissue), secondary [insufficient thyroid stimulating hormone (TSH) produced from the pituitary gland] and tertiary (inadequate production of TSH-releasing factor by the hypothalamus). Acquired primary hypothyroidism accounts for over 90 per cent of all canine cases (Muller, Kirk & Scott, 1983) and results mainly from lymphocytic thyroiditis and idiopathic atrophy (Gosselin et al, 1982).…”

Thyroid function tests in dogs using radioimmunoassay kits

“…E . W I L L I A M S bound to proteins which have been identified as albumin and three globulin fractions, while the metabolically active form is the unbound or free T4 (Rosychuk, 1982). Attempts to measure this free T4, which would more accurately reflect the status of the animal than a measure of total T4, have been either too time consuming and tedious, such as equilibrium dialysis, for use in a routine clinical chemistry laboratory, or have led to an indirect measure such as the free thyroxine index .…”