Transient Prealbumin- Associated Hyperthyroxinemia in TSH-Producing Pituitary Adenoma

This case report describes a 38-year-old male who was hospitalized for further clarification of clinically mild hyperthyroidism. His increased total hormone levels, the elevated free thyroid hormones and the elevated basal TSH with blunted response to TRH strongly suggested a pituitary adenoma with inappropriate TSH incretion. Transmission computed tomography showed an intrasellar expansion, 16 mm in diameter. The neoplastic TSH production was confirmed by an elevated alpha-subunit and a raised molar alpha-sub/ATSH ratio. However, T4 distribution on prealbumin (PA, TTR), albumin (A) and thyroxine binding globulin (TBG) showed a clearly increased binding to PA (39%), indicating additional prealbumin-associated hyperthyroxinemia. The absolute values of PA, A and TBG were within the normal range. After removal of the TSH-producing adenoma, basal TSH, the free thyroid hormones and T4 binding to prealbumin returned to normal. Therefore, the prealbumin-associated hyperthyroxinemia had to be interpreted as a transitory phenomenon related to secondary hyperthyroidism (T4 shift from thyroxine binding globulin to prealbumin) rather than a genetically conditioned anomaly of protein binding.

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A longitudinal study of total and free thyroid hormones and thyroxinebinding globulin during normal puberty

Acta Endocrinologica ◽

10.1530/acta.0.1230305 ◽

1990 ◽

Vol 123 (3) ◽

pp. 305-310 ◽

Cited By ~ 17

Author(s):

David B. Dunger ◽

Janet A. Perkins ◽

Terence P. Jowett ◽

Philip R. Edwards ◽

Leslie A. Cox ◽

...

Keyword(s):

Longitudinal Study ◽

Thyroid Hormones ◽

Normal Children ◽

Thyroxine Binding Globulin ◽

Free Thyroid Hormones ◽

Pubertal Growth ◽

Normal Ranges ◽

Stage 4 ◽

Puberty Stages ◽

Males And Females

Abstract. Thyroid hormones are essential for normal pubertal growth, yet the changes in total and, especially, free thyroid hormones and thyroxine-binding globulin during puberty have not been adequately defined. Serum from 39 normal children (20 girls, 19 boys) between the ages of 10 and 15 years were assayed for total T4, free T4, free T3 and thyroxine-binding globulin at 6-monthly intervals; the free hormone assays were valid, non-analogue methodologies. In the girls, free T4 levels fell from 15.7±0.6 pmol/l at 10 years to 13.0±0.6 (p<0.001) at 12.5 years before rising to 15.9±0.7 at 15 years; this nadir occurred at puberty stages 3-4. Changes in total T4 followed a similar pattern with a slight delay in the nadir (13 years, puberty stage 4). In the boys, free T4 fell from 16.3±0.6 pmol/l at 10 years to 14.3±0.3 at 13.5 years, then rising to 15.4±0.5 at 15 years; the nadir again occurred at puberty stages 3-4. The corresponding nadir in total T4 which occurred at puberty stages 4-5 was not apparent by age analysis. Thyroxine-binding globulin concentrations remained unchanged in the girls, but fell slightly in the boys during later puberty. Free T3 concentrations in the girls showed a progressive fall after 12.5 years which was significant by the age of 14 when most had been in puberty stage 5 for more than 1 year. The boys showed no change of free T3 concentration throughout the study. These data demonstrate important differences in the levels of free thyroid hormones in males and females during puberty. Normal ranges for girls and boys between the ages of 9.5 and 15.5 years are presented.

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