An Update on the Pathophysiology and Diagnosis of Inappropriate Secretion of Thyroid-Stimulating Hormone.

Inappropriate secretion of thyroid-stimulating hormone (IST), also known as central hyperthyroidism, is a clinical condition characterized by elevated free thyroxine and triiodothyronine concentrations concurrent with detectable thyroid-stimulating hormone (TSH) concentrations. Similarly, the term syndrome of IST (SITSH) is widely used in Japan to refer to a closely related condition; however, unlike that for IST, an elevated serum free triiodothyronine concentration is not a requisite criterion for SITSH diagnosis. IST or SITSH is an important indicator of resistance to thyroid hormone ß (RTHß) caused by germline mutations in genes encoding thyroid hormone receptor ß (TRß) and TSH-secreting pituitary adenoma. Recent evidence has accumulated for several conditions associated with IST, including RTH without mutations in the TRß gene (non-TR-RTH), the phenomenon of hysteresis involving the hypothalamus-pituitary-thyroid axis (HPT-axis), methodological interference, and Cushing's syndrome after surgical resection. However, little information is available on the systematic pathophysiological aspects of IST in previous review articles. This report presents an overview of the recent advances in our understanding of the etiological aspects of IST that are relevant for diagnosis and treatment. Moreover, the report focuses on the potential mechanism of IST caused by hysteresis in the HPT-axis (lagging TSH recovery) in terms of epigenetic regulation.

An overview of thyroid function tests in subjects with resistance to thyroid hormone and related disorders.

Confirmation of sustained syndrome of inappropriate secretion of thyrotropin (SITSH) is a milestone in diagnosis of ß type of resistance to thyroid hormone (RTHß). The differential diagnoses of RTHß include TSH-producing pituitary adenoma (TSHoma) and familial dysalbuminemic hyperthyroxinemia (FDH), which also present SITSH. Recently, patients with RTHα caused by a mutation in thyroid hormone receptor α were reported and they did not present SITSH but a decline in the serum T4/T3 ratio. This review was aimed to overview thyroid function tests in RTH and related disorders. First, the characteristics of the thyroid function in RTHß, TSHoma, and FDH obtained from a Japanese database are summarized. Second, the degrees of SITSH in patients with truncations and frameshifts were compared with those in patients with single amino acid deletions and single amino acid substitutions obtained from the literature. Third, the degrees of SITSH in homozygous patients were compared with those in heterozygous patients with cognate mutations. Finally, the FT3/FT4 ratios in RTHα are summarized. In principle, the TSH values in FDH were within the normal range and apparent FT4 values in FDH were much higher than in RTHß and TSHoma. The FT3/FT4 values in RTHß were significantly lower than in TSHoma. The degrees of SITSH in patients with truncations and frameshifts were more severe than those in patients with single amino acid deletions and single amino acid substitutions, and those in homozygous patients were more severe than those in heterozygous patients with cognate mutations. The FT3/FT4 ratios in RTHα were higher than 1.0.

A remarkable case of thyrotoxicosis initially caused by graves' disease followed by a probable TSHoma - a case report.

BACKGROUND: Graves' disease is the commonest cause of thyrotoxicosis whilst thyrotropin (TSH)-producing pituitary adenomas (thyrotropinomas, TSHomas) are very rare and account for just 1-2% of all pituitary adenomas. Coexistence of a TSHoma and Graves' disease has been very rarely reported. Here, we report a case of a patient whose initial presentation with primary thyrotoxicosis due to Graves' disease, was subsequently followed by a relapse of thyrotoxicosis due to a probable TSHoma. CASE: A sixty-eight year old woman was referred to our department with classical features of thyrotoxicosis. Initial biochemistry confirmed hyperthyroxinaemia [free thyroxine (fT4) 20.4 pmol/L (reference range 7.0-16.0)] and a suppressed TSH [< 0.02mIU/L (0.50-4.20)]. A technetium pertechnetate uptake scan was consistent with Graves' Disease. She was treated with carbimazole for 18 months and remained clinically and biochemically euthyroid. After stopping carbimazole her fT4 started to rise but TSH remained normal. Laboratory assay interference was excluded. A TRH stimulation test demonstrated a flat TSH response and pituitary MRI revealed a microadenoma. Remaining pituitary hormones were in the normal range other than a slightly raised IGF-1. An 11C-methionine PET/CT scan coregistered with volumetric MRI (Met-PET-MRICR) demonstrated high tracer uptake in the left lateral sella region suggestive of a functioning adenoma. The patient declined surgery and was unable to tolerate cabergoline or octreotide. Thereafter, she has elected to pursue a conservative approach with periodic surveillance. CONCLUSION: This is a very unusual case of thyrotoxicosis caused by two different processes occurring in the same patient. It highlights the importance of considering dual pathology when previously concordant thyroid function tests become discordant. It also highlights a potential role of Met-PET-MRICR in the localisation of functioning pituitary tumours.

Dynamic changes of central thyroid functions in the management of Cushing's syndrome.

OBJECTIVE: The aim of this study was to determine the frequency of central thyroid dysfunctions in Cushing's syndrome (CS). We also aimed to evaluate the frequency of hyperthyroidism due to the syndrome of the inappropriate secretion of TSH (SITSH), which was recently defined in patients with insufficient hydrocortisone replacement after surgery. MATERIALS AND METHODS: We evaluated thyroid functions (TSH and free thyroxine [fT4]) at the time of diagnosis, during the hypothalamo-pituitary-adrenal axis recovery, and after surgery in 35 patients with CS. The patients were separated into two groups: ACTH-dependent CS (group 1, n = 20) and ACTH-independent CS (group 2, n = 15). Patients' clinical and laboratory findings were evaluated in five visits in the outpatient clinic of the endocrinology department. RESULTS: The frequency of baseline suppressed TSH levels and central hypothyroidism were determined to be 37% (n = 13) and 26% (n = 9), respectively. A negative correlation was found between baseline cortisol and TSH levels (r = -0.45, p = 0.006). All patients with central hypothyroidism and suppressed TSH levels showed recovery at the first visit without levothyroxine treatment. SITSH was not detected in any of the patients during the postoperative period. No correlation was found between prednisolone replacement after surgery and TSH or fT4 levels on each visit. CONCLUSION: Suppressed TSH levels and central hypothyroidism may be detected in CS, independent of etiology. SITSH was not detected in the early postoperative period due to our adequate prednisolone replacement doses.

Dynamic changes of central thyroid functions in the management of Cushing's syndrome

ABSTRACT Objective The aim of this study was to determine the frequency of central thyroid dysfunctions in Cushing's syndrome (CS). We also aimed to evaluate the frequency of hyperthyroidism due to the syndrome of the inappropriate secretion of TSH (SITSH), which was recently defined in patients with insufficient hydrocortisone replacement after surgery. Materials and methods We evaluated thyroid functions (TSH and free thyroxine [fT4]) at the time of diagnosis, during the hypothalamo-pituitary-adrenal axis recovery, and after surgery in 35 patients with CS. The patients were separated into two groups: ACTH-dependent CS (group 1, n = 20) and ACTH-independent CS (group 2, n = 15). Patients' clinical and laboratory findings were evaluated in five visits in the outpatient clinic of the endocrinology department. Results The frequency of baseline suppressed TSH levels and central hypothyroidism were determined to be 37% (n = 13) and 26% (n = 9), respectively. A negative correlation was found between baseline cortisol and TSH levels (r = -0.45, p = 0.006). All patients with central hypothyroidism and suppressed TSH levels showed recovery at the first visit without levothyroxine treatment. SITSH was not detected in any of the patients during the postoperative period. No correlation was found between prednisolone replacement after surgery and TSH or fT4 levels on each visit. Conclusion Suppressed TSH levels and central hypothyroidism may be detected in CS, independent of etiology. SITSH was not detected in the early postoperative period due to our adequate prednisolone replacement doses.

Familial Dysalbuminemic Hyperthyroxinemia that was Inappropriately Treated with Thiamazole Due to Pseudo-thyrotoxic Symptoms.

We herein report the case of a Japanese woman with familial dysalbuminemic hyperthyroxinemia (FDH) who was initially diagnosed with Graves' disease. Direct genomic sequencing revealed a guanine to cytosine transition in the second nucleotide of codon 218 in exon 7 of the albumin gene, which then caused a proline to arginine substitution. She was finally diagnosed with FDH, which did not require treatment. FDH is - superficially - an uncommon cause of syndrome of inappropriate secretion of thyrotropin (SITSH) in Japan. A misdiagnosis of pseudo-hyperthyroidism will lead to inappropriate treatment. Thus, physicians should strongly note the possibility of FDH as a differential diagnosis of SITSH.

A case of familial dysalbuminemic hyperthyroxinemia (FDH) in Japan: FDH as a possible differential diagnosis of syndrome of inappropriate secretion of thyroid-stimulating hormone (SITSH).

Familial dysalbuminemic hyperthyroxinemia (FDH) is an autosomal dominant condition and is the most commonly inherited euthyroid hyperthyroxinemia in Caucasians. However, it is extremely rare in Asian populations. A 30-year-old Japanese woman, who was incidentally found to have apparent thyroid dysfunction, was admitted to our hospital in 2004. She had extremely elevated serum free thyroxine (FT4), moderately elevated free triiodothyronine (FT3), and normal thyroid-stimulating hormone (TSH). Clinical thyroid examination revealed no abnormalities other than small goiter. Anti-thyroglobulin antibody titer was positive, but titers of other anti-thyroid antibodies, including antithyroid peroxidase antibody, TSH receptor antibodies, and thyroid-stimulating antibody, were negative. Levels of FT3, FT4, and TSH were similar when measured by three different laboratory kits, and FT4 was still high when measured by equilibrium dialysis. By affinity chromatography, FT4, TT4, and albumin were extracted to the same fraction, and the levels of FT4 and TT4 were extremely high. By combination of reversed phase liquid chromatography and mass spectrometry techniques, the amino acid sequence of human serum albumin was determined. The patient was found to be a heterozygote for p.R218P mutation in the gene for human serum albumin and was diagnosed as FDH. This patient, who harbored the p.R218P mutation in the albumin gene, is the fifth case report of FDH in Japan. This condition is characterized by extremely high serum FT4 and moderately high serum FT3 levels. Although rare, FDH should be considered in the differential diagnosis for syndrome of inappropriate secretion of TSH (SITSH) in Japan.

[Van Wyk-Grumbach syndrome: A case report and literature review].

Van Wyk-Grumbach syndrome (VWGS) is a rare complication of prolonged untreated juvenile hypothyroidism characterized by precocious puberty and enlarged multicystic ovaries. A 13-year-old girl visited our outpatient clinic due to menstrual irregularities. She had precocious puberty, pituitary hyperplasia and multiple cystic ovaries in addition to clinical signs of severe congenital hypothyroidism. After the initiation of L-thyroxine therapy, the symptoms were alleviated in a short time. This rare syndrome is easy to be misdiagnosed as pituitary and ovarian tumor. High degree of suspicion and timely diagnosis can prevent unnecessary surgical procedures because the symptoms can be reversed with thyroid hormone supplementation.

Van Wyk-Grumbach syndrome: A case report and literature review / 中南大学学报(医学版)

Van Wyk-Grumbach syndrome (VWGS) is a rare complication of prolonged untreated juvenile hypothyroidism characterized by precocious puberty and enlarged multicystic ovaries. A 13-year-old girl visited our outpatient clinic due to menstrual irregularities. She had precocious puberty, pituitary hyperplasia and multiple cystic ovaries in addition to clinical signs of severe congenital hypothyroidism. After the initiation of L-thyroxine therapy, the symptoms were alleviated in a short time. This rare syndrome is easy to be misdiagnosed as pituitary and ovarian tumor. High degree of suspicion and timely diagnosis can prevent unnecessary surgical procedures because the symptoms can be reversed with thyroid hormone supplementation.

A Patient With a Thyrotropin-Secreting Microadenoma and Resistance to Thyroid Hormone (P453T).

CONTEXT: Resistance to thyroid hormone (RTH) ß is due to mutations in the ß-isoform of the thyroid hormone receptor (TR). TSH-secreting adenomas (TSHomas) are presumed to represent clonal expansion and have been reported to contain TRß gene mutations. Mice with a knock-in mutation in the TRß gene spontaneously develop TSHomas, although as yet no patient has been reported to have both a TSHoma and RTHß. OBJECTIVE: We investigated a 12-year-old girl with elevated serum T4 concentration, inappropriately high TSH levels, and a pituitary adenoma. DESIGN AND INTERVENTION: Clinical, biochemical, and radiological assessments were performed at baseline and after a transsphenoidal pituitary adenomectomy. RESULTS: The patient's laboratory results included: TSH, 21.12 mIU/L (0.35-4.94 mIU/L); free T3, 14.25 pmol/L (2.63-5.7 pmol/L); free T4, 28.79 pmol/L (9.01-19.05 pmol/L); serum glycoprotein hormone alpha-subunit (α-GSU), 0.32 ng/ml (0.22-0.39 ng/ml); and α-GSU/TSH, 0.15. Thyroid radioiodine uptake was increased by 94.4% at 24 hours. A T3 suppression test showed incomplete suppression of the serum TSH concentration and blunted response of the peripheral thyroid hormone markers. The sequence of TRß exons confirmed a P453T mutation in the TRß gene. Pituitary magnetic resonance imaging revealed a microadenoma in the left side of the pituitary. The patient underwent transsphenoidal pituitary adenomectomy. Histologically, the tumor stained positively for TSH-ß, human Chorionic Gonadotropin alpha (HCG-α), GH, prolactin, and ACTH. After removal of the tumor, the patient's thyroid function improved significantly, and she experienced the onset of menarche and an increase in linear growth as well. CONCLUSIONS: This patient with RTHß had a TSHoma consistent with previous findings linking somatic TRß mutations to TSHomas.

Reduced sleep quality and depression associate with decreased quality of life in patients with pituitary adenomas.

OBJECTIVES: Several studies reported decreased quality of life (QoL) and sleep as well as increased rates of depression for patients with pituitary adenomas. Our aim was to explore to what extent differences in depression and sleep quality contribute to differences in QoL between patients with pituitary adenomas and controls. DESIGN: A cross-sectional case-control study. SETTING: Endocrine Outpatient Unit of the Max Planck Institute of Psychiatry, Munich, Department of Internal Medicine, Ludwig-Maximilians-University, Munich, and the Institute of Clinical Psychology and Psychotherapy, Technical University, Dresden. PARTICIPANTS: Patients with pituitary adenomas (n=247) and controls (from the DETECT cohort, a large epidemiological study in primary care patients) matched individually by age and gender (n=757). MEASUREMENTS: Sleep quality was assessed with the Pittsburgh Sleep Quality Index (PSQI) and QoL was measured by the generic EQ-5D and calculated by the time trade-off- and VAS-method. Depression was categorized as 'no depression', 'subclinical depression', and 'clinical depression' according to the Beck Depressions Inventory for patients and the Depression Screening Questionnaire for control subjects. STATISTICAL ANALYSES: General linear and generalized, logistic mixed models as well as proportional odds mixed models were calculated for analyzing differences in baseline characteristics and in different subgroups. RESULTS: Patients with pituitary adenomas showed decreased QoL (VAS index: 0.73±0.19) and sleep (PSQI score: 6.75±4.17) as well as increased rates of depression (subclinical or clinical depression: 41.4%) compared with their matched control subjects (VAS index: 0.79±0.18, PSQI score: 5.66±4.31, subclinical or clinical depression: 25.9%). We have shown that a substantial proportion of the reduced QoL (48% respectively 65%) was due to the incidence of depression and reduced sleep quality. CONCLUSIONS: These findings emphasize the importance of diagnosing depressive symptoms and sleep disturbances in patients with pituitary disease, with the ultimate goal to improve QoL in patients with pituitary adenomas.

Outcomes of endoscopic transsphenoidal pituitary surgery.

Since the 1990s, endoscopic transsphenoidal surgery for pituitary adenomas has increased in popularity. Outcomes of endoscopic surgery for clinically secretory adenomas are favorable, and results for nonfunctional tumors reveal high rates of complete resection, improvements in vision, and low rates of complications. This article discusses some of the recent studies reporting outcomes from endoscopic series for Cushing disease, acromegaly, prolactin-secreting tumors, and nonfunctioning macroadenomas.

Pituitary tumor management in pregnancy.

The improved management of pituitary adenomas has led to an increasing number of pregnancies in patients harboring pituitary adenomas. Therefore, adequate management of pregnant women with pituitary adenomas is of growing importance. Because pregnancy produces several physiologic changes to the endocrine system, especially to the pituitary gland, endocrinologists must be knowledgeable and skilled to effectively manage pregnant women with pituitary adenomas and to guarantee the wellbeing of the fetus.

[Endocrine abnormalities in a patient with borderline personality disorder--case 8/2014]. / Endokrinopathie bei einer Patientin mit Persönlichkeitsstörung vom Borderline-Typ--Fall 8/2014.

HISTORY AND ADMISSION FINDINGS: We report on a 44-year-old woman who was treated for borderline personality disorder in the Department of Psychiatry. In addition, symptoms of hyperthyroidism (anxiety, weight loss, hyperdefecation) were noticeable. Thyroid stimulating hormone (TSH) was marginally elevated, free triiodothyronine (T3) and free thyroxine (T4) were clearly elevated. Hence, the patient was transferred to the Department of Endocrinology. INVESTIGATIONS: Thyroid ultrasound revealed a diffuse goiter with a total volume of 24,8 ml. Antibody screening did not show elevated titers. The thyrotropin releasing hormone (TRH) test depicted a blunted TSH response. Serum levels of free glycoprotein hormone alpha-subunit, prolactin and insulin-like growth factor 1 were increased. DIAGNOSIS, TREATMENT AND COURSE: In cranial magnetic resonance imaging (MRI), a hypointense lesion on the left side of the anterior pituitary gland was detected indicating a thyrotropin-secreting microadenoma with concomitant secretion of prolactin and possible secretion of human growth hormone (HGH). A thyreostatic therapy was initiated aiming at euthyreosis. For symptom control, betablockers were administered. Subsequently, the patient underwent an uncomplicated transsphenoidal resection. Histological examination confirmed the diagnosis of a pituitary adenoma with expression of TSH, prolactin and HGH. As expected, thyroid hormones declined afterwards. CONCLUSIONS: TSHoma is rare. Diagnosis is confirmed by endocrinological testing and cranial imaging. Therapeutic options comprise transsphenoidal adenomectomy, drug therapy (somatostatin analogues, dopaminergic agonists) and irradiation. Resistance to thyroid hormones should be included in the differential diagnosis.

Clinical and genetic characteristics of a large monocentric series of patients affected by thyroid hormone (Th) resistance and suggestions for differential diagnosis in patients without mutation of Th receptor ß.

OBJECTIVE: The syndrome of resistance to thyroid hormone (RTH) is caused by a mutation of TH receptor ß (TRß) in 80% of cases. Patients without mutation (non-TR-RTH) may have a biochemical pattern that is difficult to differentiate from that of pituitary TSH-secreting adenoma (TSHoma). Herein, we report a large monocentric series of RTH focusing on patients with non-TR-RTH, to evaluate possible clinical or biochemical parameters able to distinguish them from TSHoma. DESIGN AND PATIENTS: We retrospectively reviewed the data of 99 consecutive patients with inappropriate TSH secretion (IST) syndrome referred to our Department between 1983 and 2011, identifying 68 patients with RTH and 31 patients with TSHomas. MEASUREMENTS: Patient records were reviewed for the main clinical, biochemical and imaging characteristics. RESULTS: Of our 68 patients with RTH, 16 (23·5%) did not show a TRß mutation and did not have affected family members. Of these 16 patients, three developed a TSHoma, during follow-up. To distinguish non-TR-RTH from TSHoma, we identified appropriate cut-off values for the main biochemical parameters that demonstrated the greatest sensitivity and specificity (T3 suppression test, α-subunit/TSH molar ratio, α-subunit assay and TRH test) and we calculated the probability for each patient to develop a TSHoma. CONCLUSIONS: The application of the identified cut-offs could become a very useful tool in the challenging differential diagnosis between sporadic non-TR-RTH and TSHoma. It would then be possible to select the patients at higher risk of developing a TSHoma and therefore needing a closer follow-up.

[Thyroid disease caused by receptor abnormality].

Hormone receptor abnormality is a syndrome of an abnormal mechanism caused by defective receptor function in hormone action. Resistance to thyroid hormone is a syndrome in which the responsiveness of the target organ to thyroid hormone is reduced. Resistance to thyroid hormone exhibits unsuppressed thyrotropin(TSH) despite elevated free thyroxin (FT4) and free 3,5,3'-triiodothyronine (FT3), termed the syndrome of the inappropriate secretion of TSH (SITSH). Resistance to thyroid hormone is mainly caused by a mutation in the thyroid hormone receptor beta (TRbeta) gene. Genetic analysis of the TRbeta gene is important to diagnose resistance to thyroid hormone. TSH receptor (TSHR) abnormality is classified as a gain-of-function mutation and loss-of-function mutation. Loss-of-function mutations in the TSHR gene occur as TSH resistance, which is found to have euthyroid hyperthyrotropinemia or hypothyroidism because of the reduced responsiveness of the receptor to TSH. R450H mutation in the TSHR gene is occasionally observed in Japanese patients with TSH resistance. In Japan, it is suggested that analysis of the R450H mutation in the TSHR gene is useful to determine the cause of hyperthyrotropinemia or hypothyroidism.

Sixteen years post radiotherapy of nasopharyngeal carcinoma elicited multi-dysfunction along PTX and chronic kidney disease with microcytic anemia.

BACKGROUND: The hypothalamic-pituitary (h-p) unit is a particularly radiosensitive region in the central nervous system. As a consequence, radiation-induced irreversible, progressively chronic onset hypopituitarism (RIH) commonly develops after radiation treatments and can result in variably impaired pituitary function, which is frequently associated with increased morbidity and mortality. CASE PRESENTATION: A 38-year-old male subject, previously having received radiotherapy for treatment of nasopharygeal carcinoma (NPCA) 16 years ago, appeared at OPD complaining about his failure in penile erection, loss of pubic hair, atrophy of external genitalia: testicles reduced to 2×1.5 cm; penile size shrunk to only 4 cm long. Characteristically, he showed extremely lowered human growth hormone, (HGH, 0.115 ng/mL), testosterone (<0.1 ng/mL), total thyroxine (tT4: 4.740 g/mL), free T4 (fT4, 0.410 ng/mL), cortisol (2.34 g/dL); lowered LH (1.37 mIU/mL) and estradiol (22 pg/mL); highly elevated TSH (7.12 IU/mL). As contrast, he had low end normal ACTH, FSH, total T3, free T3, and estriol; high end normal prolactin (11.71 ng/mL), distinctly implicating hypopituitarism-induced hypothyroidism and hypogonadism. serologically, he showed severely lowered Hb (10.6 g/dL), HCT (32.7%), MCV (77.6 fL), MCH (25.3 pg), MCHC (32.6 g/dL), and platelet count (139×103/L) with extraordinarily elevated RDW (18.2%), together with severely lowered ferritin (23.6 ng/mL) and serum iron levels; highly elevated total iron binding capacity (TIBC, 509 g/dL) and transferrin (363.4 mg/dL), suggesting microcytic anemia. Severely reduced estimated glomerular filtration rate (e-GFR) (89 mL/mim/1.73 m2) pointed to CKD2. Hypocortisolemia with hyponatremia indicated secondary adrenal insufficiency. Replacement therapy using androgen, cortisol, and Ringer's solution has shown beneficial in improving life quality. CONCLUSIONS: To our believe, we are the first group who report such complicate PTX dysfunction with adrenal cortisol insufficiency concomitantly occurring in a single patient.

[TSH secreting adenoma of pituitary gland (TSHom) - rare cause of hyperthyroidism in pregnancy]. / TSH-sezernierendes Hypophysenadenom (TSHom) - seltene Ursache einer Hyperthyreose in der Schwangerschaft.

HISTORY AND ADMISSION FINDINGS: A 28 year-old woman in her first pregnancy was referred to the department of obstetrics and gynecology at 24 weeks of gestation because of pregnancy-induced hypertension. INVESTIGATIONS: Thyroid stimulating hormone (TSH), free T3 and free T4 were elevated. Antibody screening did not show antithyroid peroxidase (anti-TPO) antibodies and TSH receptor antibodies. Clinical findings were suspicious of TSH secreting pituitary tumour (TSH-om) or thyroid hormone resistance (RTH). In absence of clinical sings of elevated intracranial pressure magnetic resonance imaging (MR) was discussed but not carried out and planned after delivery. A visual-field defect was ruled out by orbital field evaluation. TREATMENT AND COURSE: Treatment with 3 × 50 mg propylthiouracil daily was initiated. However, normal fT3/fT4 titers could not be achieved. Serum levels were in the high normal ranges and TSH remained increased. The clinical situation of the patient improved resulting in a normal delivery at term. The healthy newborn was breast feed and MR imaging of the mother revealed a 5×8 mm tumor of the pituitary gland. CONCLUSION: In pregnant women with pregnancy-induced hypertension thyroid diseases have to be ruled out. Rare causes of hyperthyreoidism are TSH secreting pituitary tumors or thyroid hormone resistance (RTH). Treatment of choice for hyperthyreoidism in pregnancy is propylthiouracil. Normal vaginal delivery and breast feeding are possible. Following delivery it is mandatory to determine an individual treatment strategy.

[Syndromes of resistance to thyroid hormone and inappropriate secretion of TSH (SITSH)].

Resistance to thyroid hormone (RTH) is a syndrome in which the responsiveness of end organs to thyroid hormone (TH) is reduced. Given that the TH-responsive end-organs include pituitary thyrotrophs, almost all patients with RTH manifest unsuppressed thyrotropin (TSH) despite elevated free-T4 and free-T3 levels. This abnormal finding in the thyroid function test is termed "syndrome of inappropriate secretion of TSH" (SITSH) or "central hyperthyroidism". Patients with TSH-secreting pituitary tumors(TSHoma) also manifest SITSH. Thus, the differential diagnosis of RTH vs. TSHoma is sometimes difficult and challenging. In this review article, the etiology of RTH and diagnostic approach for SITSH are explained and an algorithm for differential diagnosis of RTH vs. TSHoma is proposed.

Falso incremento de la hormona estimulante del tiroides asociado a la presencia de macro-TSH / Falsely elevated levels of thyrotropin caused by macro-TSH

Mujer que presentó un importante incremento de la hormona estimulante del tiroides (TSH) (62,2 mU/L) con hormonas tiroideas dentro de los intervalos de referencia. La paciente se encontraba eutiroidea y no presentaba bocio. Se realizó un estudio inicial para determinar la posible causa del incremento en la concentración de TSH. La recuperación de TSH tras precipitación con polietilenglicol fue del 1%, sugiriendo la presencia de alguna molécula de elevado peso molecular que podría interferir en la determinación. Mediante cromatografía de exclusión, se confirmó la presencia de macro-TSH, un complejo autoinmune formado por TSH unido a una Inmunoglobulina G que es inmunorreactivo pero biológicamente inactivo, por lo que, si no se detecta, induce a una interpretación errónea de la concentración de TSH (AU)

Woman showing an important increase of serum TSH (62.2 mU/L) with thyroid hormones within the reference interval. The patient was clinically euthyroid and without goitre. Investigations were carried out to determine the origin of the unexpected high TSH. Polyethylene glycol precipitation test showed low TSH recovery (1%), indicating the presence of large molecules that could interfere with the measurement. The serum sample was fractionated by gel filtration chromatography and the presence of a macro-TSH form was confirmed, an immunoreactive but biologically inactive TSH-Immunoglobulin G autoantibody complex. Its detection is important to avoid a misleading interpretation of the TSH concentration (AU)