Abstract. Sixteen patients with congenital goitre were submitted to a bovine TSH stimulation test (bTSH), and serum thyroid hormones (T3, T4), TSH and thyroglobulin (Tg) were measured before and after bTSH injection. In 9 patients with an organification defect basal levels of Tg were normal (19.4 ± 3.1 μg/l) rising after bTSH to a mean level ± sem of 37.3 ± 4.1 μg/l. Six patients with defective Tg synthesis or release had a mean basal level of serum Tg of 8.7 ± 1.9 μg/l (mean ± sem) and failed to raise serum Tg concentrations after bTSH (mean ± sem: 10.4 ± 2.1 μg/l). In both groups a modest although significant (P < 0.05) change in serum thyroid hormones after bTSH was noted. We conclude that the bTSH test may be used to distinguish the group with defective Tg synthesis or release from other types of congenital goitre.
Geraldo A. Medeiros-Neto, José A. Marcondes, Humberto Cavaliere, Bernardo L. Wajchenberg, and Meyer Knobel
Eduardo Gaitan, Robert C Cooksey, Jim Legan, Raymond H Lindsay, Sidney H Ingbar, and Geraldo Medeiros-Neto
Gaitan E, Cooksey RC, Legan J, Lindsay RH, Ingbar SH, Medeiros-Neto G. Antithyroid effects in vivo and in vitro of babassu and mandioca: a staple food in goiter areas of Brazil. Eur J Endocrinol 1994;131:138–44. ISSN 0804–4643
Babassu (Orbignya phalerata), a palm-tree coconut fruit, mixed with mandioca (Manihot utilissima) is the staple food of people living in the endemic goiter area of Maranhao in Brazil, where goiter prevalence among schoolchildren was still 38% in 1986 despite an adequate iodine intake in most of the population. Therefore, the question arose as to whether or not the ingestion of babassu alone or mixed with mandioca contributed to the persistence of endemic goiter in this area of Brazil. In this investigation we examined the potential antithyroid effects of babassu and mandioca by means of in vivo studies in Sprague-Dawley rats, in vitro studies in porcine thyroid slices and using a purified porcine thyroid peroxidase (TPO) system. Samples of various edible parts of babassu and mandioca flour were homogenized and extracted in goitrogen-free water (GFW) for in vivo experiments, and in methanol (100 g/l), GFW or 0.06 mol/l phosphate buffer (pH 7.0) for in vitro experiments. The edible parts of babassu produced significant in vivo antithyroid effects (p < 0.05–< 0.001) in rats on a high iodine intake (14 μg I− day−1 · rat−1), as well as distinct and reproducible antithyroid and anti-TPO activities in both in vitro systems, their action being similar to that of the thionamide-like antithyroid drugs propylthiouracil and methimazole. The antithyroid action of aqueous extracts of mandioca flour in vivo and in thyroid slices in vitro was also evident by significant (p < 0.01–< 0.001) and pronounced inhibition of the iodide organification process; however, in contrast to babassu, methanol and aqueous extracts of mandioca flour caused little inhibition in vitro in the TPO system. Little or no effect was produced by babassu or mandioca on thyroid iodide transport by thyroid slices or in vivo in the rat, indicating that neither thiocyanate nor perchlorate-like compounds are responsible for their antithyroid effects. Results of this study provide direct experimental evidence, both in vivo and in vitro, of antithyroid effects of babassu and mandioca, supporting the hypothesis that this staple food is responsible, at least in part, for the persistence of goiter in the iodine-supplemented endemic region of Maranhao in Brazil.
Eduardo Gaitan, Endocrinology Section (151), VA Medical Center, 1500 E. Woodrow Wilson Drive, Jackson, MS 39216, USA
Geraldo A. Medeiros-Neto, Meyer Knobel, Marcello D. Bronstein, José Simonetti, Fadlo Fraige Filho, and Emilio Mattar
A 19 year old man had congenital hypothyroidism and severely retarded development. His thyroid gland was not enlarged and laboratory findings included low serum concentration of T4 (2.8 μg/100 ml) and T3 (16 ng/100 ml) with a high level of TSH (52 μU/ml) that rose to 192 μU/ml after TRH. 131I uptake by the thyroid was normal (41.5 % at 24 h) and did not show a normal increase after exogenous TSH administration (49.5 % at 24 h). The perchlorate discharge test was negative and no antibodies against thyroid antigens were found. Studies on the biopsy specimen revealed low iodide trapping by the thyroid slices and no formation of cyclic AMP after TSH was added to the medium. The endogenous TSH of the patient was biologically active increasing cyclic adenosine monophosphate c-AMP concentration in normal thyroid slices. No thyroglobulin was found in the thyroid tissue either by immunological or ultracentrifugational methods. An increased proportion of iodoalbumin was present in the serum. We postulate that the fundamental defect in this gland is an impaired generation of c-AMP by the defective thyroid cell and deficiency of thyroglobulin formation resulting in inadequate thyroxine and triiodothyronine synthesis.
Geraldo A. Medeiros-Neto, William Nicolau, Augusta Takeda, and A. B. Ulhoa Cintra
The biochemical and morphological changes in thyroid glands were studied in 5 patients with endemic goitre in the region before and one year after the administration of iodized oil. Each patient received a tracer dose of 125I 3–5 weeks before the biopsy and another tracer of 131I 12 h before surgery. It was observed that:
- Iodine deficient goitrous glands had more protein per gram of tissue and that this was corrected by iodination.
- The goitrous glands exhibited a higher relative proportion of particulate iodoprotein that incorporates more labelled iodine in relation to time of labelling. This abnormal situation is reverted to normal by iodination.
- A significantly higher proportion of T3 + T4 is synthetized by the glands treated with iodized oil.
- The increased amount of 127I per gram of tissue is followed by an increased iodination level of thyroglobulin.
- The ultracentrifugal pattern of proteins observed for iodine deficient glands differed from the iodinated glands, indicating a failure of maturation of thyroglobulin and possibly a greater than normal degree of heterogeneity.
- The shift in sedimentation pattern was clearly induced by the increased degree of iodination, as shown by the iodized oil injection.
- The increased cellularity and the higher rate of protein synthesis in the goitrous glands are reverted to normal after the iodized oil injection.
Rosalinda Y A Camargo, Eduardo K Tomimori, Solange C Neves, Ileana G S Rubio, Ana Luiza Galrão, Meyer Knobel, and Geraldo Medeiros-Neto
To evaluate the prevalence of chronic autoimmune thyroiditis (CAT) and iodine-induced hypothyroidism, hyperthyroidism (overt and subclinical), and goiter in a population exposed to excessive iodine intake for 5 years (table salt iodine concentrations: 40–100 mg/kg salt).
This was a population-based, cross-sectional study with 1085 participants randomly selected from a metropolitan area in São Paulo, Brazil, and conducted during the first semester of 2004.
Thyroid ultrasound examination was performed in all participants and samples of urine and blood were collected from each subject. Serum levels of thyroid-stimulating hormone, free thyroxine, and anti-thyroid peroxidase (TPO) antibodies, urinary iodine concentration, thyroid volume, and thyroid echogenicity were evaluated. We also analyzed table salt iodine concentrations.
At the time the study was conducted, table salt iodine concentrations were within the new official limits (20–60 mg/kg salt). Nevertheless, in 45.6% of the participants, urinary iodine excretion was excessive (above 300 μg/l) and, in 14.1%, it was higher than 400 μg/l. The prevalence of CAT (including atrophic thyroiditis) was 16.9% (183/1085), women were more affected than men (21.5 vs 9.1% respectively, P=0.02). Hypothyroidism was detected in 8.0% (87/1085) of the population with CAT. Hyperthyroidism was diagnosed in 3.3% of the individuals (36/1085) and goiter was identified in 3.1% (34/1085).
Five years of excessive iodine intake by the Brazilian population may have increased the prevalence of CAT and hypothyroidism in subjects genetically predisposed to thyroid autoimmune diseases. Appropriate screening for early detection of thyroid dysfunction may be considered during excessive nutritional iodine intake.