Thyroid growth

Biebermann H, Winkler F, Kleinau G (2010) Genetic defects, thyroid growth and malfunctions of the TSHRin pediatric patients. Front Biosci (Landmark Ed) 15 913-933... 

Clinical disorders of the thyroid can result from excessive or deficient production of thyroid hormone or from disorders of thyroid growth. 

Disorders of Thyroid Growth Disorders of thyroid growth include diffuse enlargement of the thyroid gland, or goiter, nodular thyroid disease, and thyroid cancer. Goiter may be associated with hypothyroidism and the resultant TSH-induced hypertrophy and hyperplasia of thyroid cells. 

Autoregulation of Thyroid Growth and Function by Iodine Independent Regulation of the Thyroid Gland by lodocompounds... 

Iodine has a direct effect on thyroid function and growth, independent of pituitary TSH regulation in vivo, as well as in vitro. Because the action of iodine is inhibited by compounds inhibiting peroxidase activity such as MMI or PTU, and thyroid hormones have no direct effect on thyroid growth and function, other... 

For delayed effects of iodide, it is difficult to separate the direct effects on the thyroid and the secondary action on thyroid hormone synthesis, secretion and serum levels, unless the experiments are performed in hypophysect-omized animals or subjects, or as responses to administered TSH. An effect of iodide on a hypophysectomized animal has been shown for (1) the inhibition of TSH-induced thyroid hormone synthesis (Katakai and Yamada, 1966) (2) the trapping of iodide (Taurog et ai, 1958) (3) the inhibition of TSH-induced thyroid hormone secretion Yamada and Lewis, 1968) or spontaneous secretion in autonomous adenomas (Green and Ingbar, 1962) and (4) the inhibition of TSH-induced thyroid growth (Bray, 1968). Of course, direct effects in vitro are also independent of the T4—TSH loop, but their in vivo relevance should be proved these effects are examined in Chapter Mechanism(s) of Action of Iodide, third part. 

Daily intraperitoneal injection of 6-iodolactone, w-iodolactone, or its free acid derivative into rats reduced the increase in thyroid weight resulting from chronic stimulation by TSH induced by methimazole administration (Pisarev et al, 1988) the three compounds had roughly equivalent effects. The inhibition of thyroid growth was not mediated by iodide released by deiodination of these compounds, because methimazole had no effect impaired organification. It was associated with a decrease in the thyroid cAMP content. In vitro, w-iodolactone inhibited the proliferation of FRTL-5 cells at pM concentrations, and was more potent than 6-iodolactone (Pisarev et al,... 

There is a further decrease in the iodine, Total T4, and Total T3 contents of the thyroid to about 25% of C values. There is also a marked increase in circulating TSH. In contrast, thyroid weight is hardly affected by the increase in TSH, a finding consistent with the concept that thyroid growth is mainly determined by autoregulatory processes not only in mild, but also in moderate, ID. 

On the strength of findings reported initially in sporadic goiter (32), it has been suggested that goiter in endemic areas could be due to thyroid-growth-promoting antibodies, TGI (33-38). 

In addition, there is now a keen controversy over the possible role of thyroid-growth-blocking antibodies of maternal origin in the etiology of sporadic congenital hypothyroidism (39-41). 

H.A. Drexhage, G.F. Botazzo, D. Doniach, L. Bitensky and J. Chayen, Evidence for thyroid growth stimulating immunoglobulins in some goitrous thyroid diseases. Lancet ii 287-292 (1980). 

R. Docter, G.F. Botazzo and D. Doniach, Further studies on thyroid growth-stimulating immunoglobulins in euthyroid non endemic goitre,... 

A. Halpern, G. Medeiros-Neto and L.D. Kohn, Thyroid growth promoting activity in endemic goiter, "The thyroid and autoimmunity",... 

P.A. Wadeleux and R.J. Winand, Thyroid growth modulating factors in the sera of patients with simple non-toxic goitre, Acta Endocrinol. 

R.D. Van Der Gaag, H.A. Drexhage and J.H. Dussault, Role of maternal immunoglobulins blocking TSH-induced thyroid growth in sporadic forms of congenital hypothyroidism. Lancet i 246-250 (1985). 

Doniach, I., 1960, Types of thyroid growth, Brit. med. Bull. 16 99. 

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