Thyroid disease is defined as a condition of malfunction of thyroid.
Hyperthyroidism is a condition in which the thyroid gland is over active
and produces too much thyroid hormones. Hypothyroidism is a condition
in which the thyroid gland is under active and produces very little
thyroid hormones. Thyroid cancer is defined as condition in which the
cells in the thyroid gland have become cancerous.
Thyroid hormone resistance syndrome
Thyroid hormone resistance syndrome is defined as a condition of which
affected individuals have elevated serum thyroid hormone levels and
inappropriately normal or elevated thyroid-stimulating hormone (TSH) but
are usually clinically euthyroid and require no treatment. Selective
pituitary resistance to thyroid hormone (PRTH) is characterized by
resistance in the pituitary gland but not in peripheral tissues(a).
C. Complications and diseases associated to Thyroid hormone resistance
C.1. Complications
1. Growth retardation/short stature and skeletal dysplasia
There is a report of a first human cases (female, age 6 y; father and
daughter, ages 47 and 11 y, respectively) with growth retardation/short
stature, skeletal dysplasia, constipation, and defective thyroid
receptor α (TRα)(14).
2. Thyroxine excess and inappropriate TSH secretion
Resistance to thyroid hormone (RTH) is an uncommon inherited cause of
hyperthyroxinemia with inappropriate TSH secretion, according to the
study by the University of Cambridge, Addenbrooke’s Hospital, United
Kingdom(15).
3. Cardiovascular risk
RTH patients show evidence in this study of increased augmentation index
consistent with an increase in arterial stiffness compared with
euthyroid controls. They also demonstrate elevated LDL-cholesterol
levels. Both these measures may lead to increased cardiovascular
risk(16).
C.2. Diseases associated to Thyroid hormone resistance
1. Differentiated thyroid cancer (DTC)
There are reports of four unusual cases of DTC associated with TSHoma (2
cases), RTH (1 case), and an elevated TSH of unknown etiology (1
case)(17).
2. A pituitary tumor
There is a report of a woman in whom the standard evaluation for
inappropriate TSH secretion was insufficient to distinguish these
entities. The patient had a low-normal TRH stimulation test and an
unmeasurable alpha-glycoprotein subunit level; however, a pituitary
magnetic resonance imaging (MRI) revealed an adenoma. More testing using
a T3 suppression test supported a RTH diagnosis and a R438H mutation
was found in the TR-beta gene. To our knowledge, this represents the
first report of an apparently incidental pituitary adenoma in the
setting of documented resistance to thyroid hormone. As such, it raises
the question of whether RTH predisposes to pituitary hyperplasia and
adenoma. development(18).
3. Papillary thyroid carcinoma
There is an association of thyroid hormone resistance syndrome and papillary thyroid carcinoma(19).
4. Immune thrombocytopenic purpura (ITP)
There is a report of a 9-year-old girl presented with ITP and features
of hypothyroidism in the form of goiter and growth retardation. She was
subsequently found to have RTH. High-dose thyroid hormone replacement
was required to overcome the resistance that not only ameliorated the
features of hypothyroidism but also brought an apparent remission of
ITP(20).
5. Postpartum thyroiditis
there is a repopt of a report of a unique case of a woman affected by
RTH, due to a novel mutation V283A in THRB, who experienced PPT with a
severe thyrotoxic phase after both her pregnancies. The association
between RTH and PPT has never been reported in the literature. In
particular, the marked suppression of TSH occurring when levels of TH
are particularly elevated is not a frequent condition during RTH(21).
6. Chronic thyroiditis
There is a report of the five-year medical history of a Japanese woman
and her father with RTH and coincidental chronic thyroiditis(22).
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Sources
(14) http://www.ncbi.nlm.nih.gov/pubmed/23940126
(15) http://www.ncbi.nlm.nih.gov/pubmed/7998483
(16) http://www.ncbi.nlm.nih.gov/pubmed/18803680
(17) http://www.ncbi.nlm.nih.gov/pubmed/23553855
(18) http://www.ncbi.nlm.nih.gov/pubmed/11327621
(19) http://www.ncbi.nlm.nih.gov/pubmed/23457315
(20) http://www.ncbi.nlm.nih.gov/pubmed/23382302
(21) http://www.ncbi.nlm.nih.gov/pubmed/23134553
(22) http://www.ncbi.nlm.nih.gov/pubmed/16723809
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