We report a 3-year-old boy with a rare somatic TSHR mutation causing autonomous adenoma of the thyroid gland in order to illustrate how the genetic analysis of the lesion impacted on the surgical strategy.
A623F and I635V are two naturally occurring TSH receptor mutations that increase basal cAMP accumulation and consequently promote the development of toxic follicular thyroid adenoma. cAMP response to increasing TSH dose is retained by A623F and I635V mutated receptors and the maximal stimulation obtained is not different from that of the wild-type receptor.
Our data suggest that the differences between functioning and nonfunctioning thyroid adenomas are restricted to the genetic mutations of the TSH-r, to the hormonal status of tumors, and to the proliferative activity, not involving markers of apoptosis control and angiogenesis.
No somatic mutation of TSH receptor was found in his thyroid adenoma and no known genetic mutations of ionic channel genes, such as calcium (CACN1S), sodium (SCN4A) and potassium (KCNE3), were found.
We screened for mutations of thyroid-stimulating hormone receptor and Gs-alpha protein genes, as these mutations are common in thyroid adenomas.We did not identify any mutations.
Ten years after the first description of activating mutations in the thyroid stimulating hormone receptor (TSHR) gene in sporadic autonomous hyperfunctioning thyroid adenomas, there is general agreement in assigning a major pathogenic role of this genetic abnormality, acting via the constitutive activation of the cAMP pathway, in both the growth and functional characteristic of these tumours.
The thyrotropin receptor (TSH-R) and Gsalpha become oncogenic through point mutation and are associated with the development of toxic thyroid adenomas.
Activating mutations in the gene encoding the alpha subunit of the stimulatory G protein (Gs alpha), as well as activating mutations in the gene encoding thyrotropin receptor in hyperfunctioning thyroid adenomas, have been reported.
Activating mutations of Gs alpha protein (gsp) and TSH receptor (TSH-R) identified in autonomously hyperfunctioning thyroid adenomas have been proposed as the primary event responsible for this disease.
Genomic DNA extracted from 15 thyroid adenomas and surrounding quiescent thyroid tissues was used as a template to amplify four DNA fragments of TSH receptor and one DNA fragment of Gs alpha.
In iodine deficiency areas, activating mutations in the TSH receptor and Gs-alpha gene are found in the majority of toxic thyroid adenomas and in some toxic goiter nodules.
In conclusion, our findings show for the first time that gain-of-function TSHr mutations are not only present in hyperfunctioning thyroid nodules with the histological features of the true thyroid adenomas, but also in hyperfunctioning hyperplastic nodules contained in the same multinodular goiter.
In conclusion, the present data, together with our previous data on the TSH receptor, suggest that oncogenic mutations of the Gs alpha as well as the TSH receptor do not seem to play a major role in tumorigenesis of autonomously functioning thyroid adenomas in Japan.
The genes for either the TSH receptor (TSH-R) or the stimulatory guanine nucleotide-binding protein subunit (Gs alpha) can undergo somatic mutations in thyroid cells, leading to constitutive activation of adenylyl cyclase and the formation of clonal hyperfunctioning thyroid adenomas.
Certainly, the recent detection of activating mutations in the TSH receptor and the Gs alpha gene in a subset of toxic thyroid adenomas and nodules may explain the generation of hyperfunction in these tumors, but there is strong evidence that these mutations are not the unique and primary cause of tumor formation.
Constitutively activating mutations have recently been identified in the thyrotropin receptor (TSHR) of hyperfunctioning thyroid adenomas and familial hyperthyroidism.
The mutations found in the thyroid-stimulating hormone (TSH) receptor are restricted to cells of hyperfunctioning thyroid adenomas and other thyroid tumors.