Goitrous hypothyroidism

Goitrous hypothyroidism has rarely been described in patients taking ethionamide (393), with recovery after withdrawal (394). Ethionamide inhibits both the uptake of iodine and its incorporation into trichloroacetic acid-precipitable protein (395). 

Drucker D, Eggo MC, Salit IE, Burrow GN. Ethionamide-induced goitrous hypothyroidism. Ann Intern Med 1984 100(6) 837-9. 

Goitrous hypothyroidism has rarely been described in patients taking ethionamide (7), with recovery after... 

Primary goitrous hypothyroidism results when the synthesis of T4 and T3 is impaired, either because of some extrinsic factor or because of an intrinsic, inherited defect in thyroid hormone biosynthesis. As a result, the positive feedback loop causes compensatory thyroid enlargement (goiter) through the hypersecretion of TRH and TSH. Primary nongoitrous hypothyroidism is characterized by loss or atrophy of thyroid tissue, resulting in decreased production of thyroid hormones despite maximum stimulation by TSH. Hashimotos thyroiditis is the most frequent cause of primary hypothyroidism in developed countries where iodine intake is sufficient. Worldwide, iodine deficiency is the most common cause of goitrous hypothyroidism. The... 

Okamura et al. (1978) Case report Japan Development of goitrous hypothyroidism and Hashimoto s thyroiditis after ingestion of large amounts of seaweed... 

Yoshinari et al. (1983) Observational study Japan Normalization of thyroid function in patients with goitrous hypothyroidism and preserved thyroid radioactive iodine uptake after avoidance of foods rich in iodine... 

Okamura et al. (1994) Observational study Japan Reversible recovery of thyroid function after iodine restriction in patients with juvenile goitrous hypothyroidism and high thyroidal radioactive iodine uptake despite chronic lymphocytic thyroiditis... 

In contrast, a woman with goitrous hypothyroidism due to Hashimoto s thyroiditis, which was being treated with 125 micrograms of levothyroxine sodium daily, developed evidence of hypothyroidism (elevated TSH) on two occasions while taking lovastatin 20 or 60 mg daily. No clinical signs of hypothyroidism developed, apart from some increased fatigue, and possibly an increased sensitivity to insulin. The author suggested that lovastatin may have influenced the absorption or clearance of levothyroxine. ... 

After parturition the mother s thyroid function tests were normal, as were thyroglobulin and thyroperoxidase TSH receptor antibodies were undetectable. Her thyroid was not palpable, but a scan showed diffuse enlargement and uptake was increased. She developed a multinodular goiter 4 years later, but free thyroxine and TSH concentrations remained normal. Three more children born to mothers using penicillamine all had subclinical hypothyroidism. The authors hypothesized that penicillamine inhibits thyroid hormone iodination and coupling reactions catalysed by thyroid peroxidase, and concluded that in utero exposure to penicillamine may cause congenital goitrous hypothyroidism and persistent subclinical hypothyroidism in older children. 

Ribault V, Castanet M, Bertrand AM, Guibourdenche J, Vuillard E, Luton D, Polak M. French Fetal Goiter Study Group. Experience with intraanmiotic thyroxine treatment in nonimmune fetal goitrous hypothyroidism in 12 cases. J Clin Endocrinol Metab 2009 94(10) 3731-9. 

Groppel etal. (1986) found that the mating frequency of goats and sheep fed casein, starch and cellulose diets without additional iodine was similar to that of animals given supplemental iodine (0.4mg.iodine/kg.diet). However, the dietary iodine deficit increased the abortion rate. As with hypothyroid sows, the gestation period was prolonged and the live-born goitrous kids were less viable than controls. 

In another study conducted on schoolchildren from Delhi, the authors reported that 28.3% of goitrous children had autoimmune thyroiditis (Gopalakrishnan et ai, 2006). They also found a small difference in the urinary iodine excretion between children with thyroid autoimmunity (166 j,g/l), as compared to goitrous children without thyroid autoimmunity (133 xg/l). Similar to the studies reported by Marwaha et al. (2000, 2003), these authors also showed a high prevalence of hypothyroidism in the children with thyroid autoimmunity. 

The pathogenesis of primary myxedema is not always easy to trace except when hypothyroidism follows thyroidectomy or massive necrosis of the thyroid. Autoimmune reactions probably are at least in some cases responsible for thyroid destruction. In myxedema, the thyroid is usually small and hard. Histologically, the typical follicular pattern has disappeared and is replaced by fibrosis. The thyroid is goitrous in a few cases, and presents the histological characteristics of hyperplasia. 

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