Irene Campi

Loss-of-function mutations in IGSF1 cause an X-linked syndrome of central hypothyroidism and testicular enlargement

Congenital central hypothyroidism occurs either in isolation or in conjunction with other pituitary hormone deficits. Using exome and candidate gene sequencing, we identified 8 distinct mutations and 2 deletions in IGSF1 in males from 11 unrelated families with central hypothyroidism, testicular enlargement and variably low prolactin concentrations. IGSF1 is a membrane glycoprotein that is highly expressed in the anterior pituitary gland, and the identified mutations impair its trafficking to the cell surface in heterologous cells. Igsf1-deficient male mice show diminished pituitary and serum thyroid-stimulating hormone (TSH) concentrations, reduced pituitary thyrotropin-releasing hormone (TRH) receptor expression, decreased triiodothyronine concentrations and increased body mass. Collectively, our observations delineate a new X-linked disorder in which loss-of-function mutations in IGSF1 cause central hypothyroidism, likely secondary to an associated impairment in pituitary TRH signaling.

The IGSF1 Deficiency Syndrome: Characteristics of Male and Female Patients

CONTEXT Ig superfamily member 1 (IGSF1) deficiency was recently discovered as a novel X-linked cause of central hypothyroidism (CeH) and macro-orchidism. However, clinical and biochemical data regarding growth, puberty, and metabolic outcome, as well as features of female carriers, are scarce. OBJECTIVE Our objective was to investigate clinical and biochemical characteristics associated with IGSF1 deficiency in both sexes. METHODS All patients (n = 42, 24 males) from 10 families examined in the university clinics of Leiden, Amsterdam, Cambridge, and Milan were included in this case series. Detailed clinical data were collected with an identical protocol, and biochemical measurements were performed in a central laboratory. RESULTS Male patients (age 0-87 years, 17 index cases and 7 from family studies) showed CeH (100%), hypoprolactinemia (n = 16, 67%), and transient partial GH deficiency (n = 3, 13%). Pubertal testosterone production was delayed, as were the growth spurt and pubic hair development. However, testicular growth started at a normal age and attained macro-orchid size in all evaluable adults. Body mass index, percent fat, and waist circumference tended to be elevated. The metabolic syndrome was present in 4 of 5 patients over 55 years of age. Heterozygous female carriers (age 32-80 years) showed CeH in 6 of 18 cases (33%), hypoprolactinemia in 2 (11%), and GH deficiency in none. As in men, body mass index, percent fat, and waist circumference were relatively high, and the metabolic syndrome was present in 3 cases. CONCLUSION In male patients, the X-linked IGSF1 deficiency syndrome is characterized by CeH, hypoprolactinemia, delayed puberty, macro-orchidism, and increased body weight. A subset of female carriers also exhibits CeH.

Rituximab treatment in a patient with severe thyroid-associated ophthalmopathy: Effects on orbital lymphocytic infiltrates

Rituximab (RTX) has been shown in previous work to improve thyroid-associated ophthalmopathy (TAO), but very little data is available on the effects of RTX in the target tissues. We studied the effects of RTX on peripheral lymphocytes and on the intra-orbital infiltrates in one patient with severe TAO who was treated with two cycles of therapy. Intra-orbital tissues derived at decompression from 3 patients with moderate-severe and 1 with severe TAO, treated with standard immunosuppression, were studied as controls. Peripheral blood lymphocytes were analyzed throughout the study period, while intra-orbital tissue lymphocytes at decompression. In the patient treated with RTX visual field and acuity improved in response to peripheral CD 20+ cell depletion, although there was a proportion of persisting CD 19+ cells. After RTX re-treatment the patients optic nerve function improved only transiently. The number of CD 20+ cells was lower in orbital tissues (0-1%) than in the peripheral blood (3%). A greater percentage of CD 19+ was observed in the orbits compared to the periphery, most of which were CD 19+5+ (80%). By immunohistochemistry, orbital tissues from all control patients showed CD 20+ and CD 3+ cells, independently of the duration of TAO and of the treatment with either steroids or radiotherapy. This is the first report on the therapeutic effect of RTX in active, severe TAO associated to the depletion of intra-orbital CD 20+ lymphocytes. After RTX, CD 19+5+ lymphocytes were shown to be 2-3 times more prevalent in the orbital infiltrates, compared to CD 20+ cells. Persistence of autoreactive cells is believed to be related to TAO relapse.

Thyrotropin-secreting pituitary adenomas: Outcome of pituitary surgery and irradiation

OBJECTIVE Our objective was to describe the effects of surgery and radiotherapy on hormonal control and tumor mass in short- and long-term follow-up of TSH-secreting pituitary adenomas (TSHomas). METHODS This was a retrospective multicenter study. RESULTS We collected data of 70 TSHomas (70% macroadenomas). The mean follow-up was 64.4 (range 3-324) months. Overall, 97% of patients were treated with surgery; in 27% of them radiotherapy was associated. After surgery, 75% of patients normalized thyroid function, 58% normalized both pituitary imaging and hormonal profile, 9% developed pituitary deficiencies, and 3% had tumor or hormonal recurrence, all within the first 2 years after surgery. Presurgical medical treatment did not significantly improve surgical outcome (63% vs 57%). Radiotherapy controlled hypersecretion in 37% of patients within 2 years, whereas 32% of patients developed new pituitary deficiencies from 18 to 96 months from treatment. At last follow-up, 80% of patients normalized thyroid function, whereas 20% were currently on medical treatment: 85% with somatostatin analog (SSA) alone and 15% with SSA combined with methimazole. Subjects who achieved disease control had surgery as the only treatment in 80% of cases and surgery combined with irradiation in 20%. CONCLUSIONS Surgery remains the first-choice treatment for TSHoma. If surgery is successful, recurrence is rare. When surgery is unsuccessful or contraindicated, SSA and radiotherapy are effective in controlling hyperthyroidism and tumor growth in the majority of patients. The effects of radiotherapy on TSH secretion and tumor mass are greater within the first years after treatment, whereas pituitary deficiencies may occur several years later.

Increased loss of the Y chromosome in peripheral blood cells in male patients with autoimmune thyroiditis

Multiple mechanisms have been proposed to explain the peculiar distribution of autoimmune thyroiditis (AIT) among women and men. Most attention has been focused on the detection of the role of estrogens and the X chromosome. Specifically, a potential role for X haploinsufficiency has been proposed in the female patient population and an association with the disease has been confirmed. Our knowledge of the etiopathogenesis of autoimmunity in male patients remains, however, limited. Next to the possible role of androgens and their imbalances, the Y chromosome appears as a potential candidate for influence of the immune function in men. Herein we analyzed a population of male patients with AIT (n=31) and healthy controls (n=88) to define a potential association of disease and the loss of the Y chromosome. Y chromosome loss increases in AIT compared to unaffected subjects; these phenomenon increases with aging as expected, however, the degree of loss is significantly increased in the patient population compared to the healthy controls. We were, thus, able to confirm the existence of an analogous mechanism in the male population to previously identified X haploinsufficiency in female patients with AIT. We propose that this commonality might represent a relevant feature in the etiopathogenesis of AIT that should be further investigated.

Rituximab induces distinct intraorbital and intrathyroidal effects in one patient satisfactorily treated for graves' ophthalmopathy

Hyperthyroid Graves’ disease (GD) is a B-cell-mediated disease caused by antibodies stimulating the thyroid stimulating hormone (TSH) receptor (TRAb). A proportion of patients (40–60%) present with an associated ophthalmopathy (TAO), a progressive inflammatory autoimmune disease of the retroorbital tissue. We thought that the anti-CD20 monoclonal antibody rituximab (RTX), by inducing transient B-cell depletion, may potentially modify the active inflammatory phase of TAO. One patient with GD and TAO in its active phase and unresponsive to steroid, was treated with RTX. Whereas the ophthalmopathy responded to RTX therapy and a decrease in the clinical activity score from 5 to 2 was observed during the B-cell depletion, serum antithyroid antibodies, and in particular serum TRAb, were not affected by therapy. When the patient underwent total thyroidectomy, we found B-cells in the thyroid tissue specimens. The eye disease remained stable (clinical activity score = 2) and the patient subsequently underwent orbital decompression to correct proptosis of the eye. At that time we did not find lymphocytes in any of the orbital tissue specimens. We believe that RTX therapy in GD may cause amelioration of ophthalmopathy by depleting total lymphocyte population in the orbit, but not lymphocyte depletion in thyroid tissue with consequent unchanged serum TRAb levels.

TGB Deficiency: description of two novel mutations associated with complete TBG deficiency and review of the literature

Thyroxine-binding globulin (TBG) is the main thyroid hormone transport protein in serum. Inherited TBG defects lead to a complete (TBG-CD) or a partial (TBG-PD) deficiency and have a diagenic transmission, being clinically fully expressed only in hemizygous males and in homozygous females. In the present study, seven patients from two unrelated families with TBG-CD were studied and two novel TBG mutations were documented. In particular, a T insertion at the 5′ donor splice site of exon 0, between nucleotides 2 and 3 at the beginning of intron 1 (g.IVS1+2_3insT) was found in one family and was named TBG-Milano. The other novel mutation is a T deletion at nucleotide 214 of exon 1, which leads to a frameshift at codon 50 with a premature stop codon at position 51 (c.214delT, P50fsX51) and was named TBG-Nikita. According to the X-linked transmission of the defect, females harboring the mutation showed a reduction in TBG levels with normal TSH and total thyroid hormone values at the lower limit of normal. Males harboring either TBG-Milano or TBG-Nikita, showed normal TSH values and low levels of total thyroid hormones and lacked TBG. In conclusion, we report two novel mutations of the TBG gene associated with a complete TBG defect. The first mutation lies at the 5′ donor splice site of exon 0 and probably alters the start of translation, while the second is a single nucleotide deletion and leads to a premature stop codon.

A Novel Albumin Gene Mutation (R222I) in Familial Dysalbuminemic Hyperthyroxinemia

Context: Familial dysalbuminemic hyperthyroxinemia, characterized by abnormal circulating albumin with increased T4 affinity, causes artefactual elevation of free T4 concentrations in euthyroid individuals. Objective: Four unrelated index cases with discordant thyroid function tests in different assay platforms were investigated. Design and Results: Laboratory biochemical assessment, radiolabeled T4 binding studies, and ALB sequencing were undertaken. 125I-T4 binding to both serum and albumin in affected individuals was markedly increased, comparable with known familial dysalbuminemic hyperthyroxinemia cases. Sequencing showed heterozygosity for a novel ALB mutation (arginine to isoleucine at codon 222, R222I) in all four cases and segregation of the genetic defect with abnormal biochemical phenotype in one family. Molecular modeling indicates that arginine 222 is located within a high-affinity T4 binding site in albumin, with substitution by isoleucine, which has a smaller side chain predicted to reduce steric hindrance, thereby facilitating T4 and rT3 binding. When tested in current immunoassays, serum free T4 values from R222I heterozygotes were more measurably abnormal in one-step vs two-step assay architectures. Total rT3 measurements were also abnormally elevated. Conclusions: A novel mutation (R222I) in the ALB gene mediates dominantly inherited dysalbuminemic hyperthyroxinemia. Susceptibility of current free T4 immunoassays to interference by this mutant albumin suggests likely future identification of individuals with this variant binding protein.

Retinal photoreceptor functions are compromised in patients with resistance to thyroid hormone syndrome (RTHβ)

Context In animal models, disruption of thyroid hormone (TH) receptor-β (TRβ) reduces the long/medium wavelength (L/M) and increases the short-wavelength (S) cones. Retinal photoreceptor (RP) functions are unknown in patients with resistance to TH syndrome (RTHβ) with dominant-negative TRβ mutations. Objective To investigate RP functions in RTHβ. Design, Setting, and Participants Case-control study involving 27 RTHβ patients and 31 age/sex-matched controls, conducted in two tertiary referral centers in Italy. Main Outcome Measures Color vision sensitivity assessed by Farnsworth; central macular thickness (CMT) of the outer retinal layer measured by spectral-domain optical coherence tomography; and retinal function tested by full-field electroretinogram (ERG) and S-cone ERG. Results Color sensitivity was worse in RTHβ patients than controls (P = 0.002). CMT was overlapping between the study groups but directly correlated with sex hormone-binding globuline levels in RTHβ. We found a significant reduction in amplitude of the cone (P = 0.024) and of the rod response (P = 0.006) in the ERG of RTHβ patients compared with controls. The response of the L/M cones measured by a specialized ERG test was lower in RTHβ than controls (P = 0.027), whereas no differences were found in the S-cone response. No correlations were found between TH levels, total error score, or electrophysiological results. Furthermore, no differences were found between patients with maternal or de novo/paternal inheritance. Conclusions We report, to our knowledge, the first in vivo evidence of functional defects of RP in RTHβ. These changes occur independently of endogenous TH levels or the prenatal exposure to high or normal maternal TH.

Severe Graves’ Orbitopathy occurring in a patient with thyroid hemiagenesis

A 64-year old woman was addressed to the endocrinology clinics, following the observation of subclinical hypothyroidism and positive anti-TPO auto-antibodies (TSH levels 6.28 uUI/ml). Ultrasound examination (Fig. 1a) showed a diffusely enlarged heterogeneous hypoechoic right lobe, with two micronodules (3 and 7 mm) and the absence of the left thyroid lobe. The patient started levothyroxine (L-T4) replacement therapy (50 μg/day), remaining euthyroid for almost 4 years. In August 2014, she presented tiredness, tremors, and palpitations with markedly increased free thyroid hormone and suppressed TSH levels. L-T4 therapy was discontinued, with no clinical improvement. On September 2014, the laboratory findings confirmed the persistence of thyrotoxicosis. The 99Tc scintiscan (Fig. 1b) showed increased uptake in the right thyroid lobe, suggesting the diagnosis of Graves’ disease which was corroborated by the demonstration of highly positive (46.2UI/L) TSH receptor antibodies (TRAb), measured using a 2nd generation TRAK human lumitest (Thermofisher, AG, Henningsdorf/ Berlin, Germany; normal value <1.8 U/L). Consequently, the patient started methymazole (MMI) treatment (30 mg/day). On November 2014, Graves’ Orbitopathy (GO) with symptomatic vertical diplopia appeared, requiring 8^ prisms for correction of constant diplopia. The Nuclear Magnetic Imaging (Fig. 1c) of the orbits showed thickening of extra-ocular muscles (medial and inferior right rectus and bilaterally superior recti). Further follow-up showed rapid progression of the GO, with deterioration of vertical diplopia. The ophthalmological assessment, according to the EUGOGO guidelines [1] demonstrated bilateral active GO with spontaneous orbital pain, chemosis, lid edema and hyperemia resulting in a clinical activity score (CAS) of 5/10. The patient presented also constant diplopia (Fig. 1d), a proptosis of 23.5/22 mm and significant worsening of eye motility. The severity NOSPECS score was 2B3A4B5060. The persistence of hyperthyroidism (TSH 0.01 mU/L, FT4 22.3 pmol/l and FT3 10.1 pmol/l) and elevated TRAb levels (41.4 U/L) required an increase of MMI to 40 mg/day. High doses of intravenous methylprednisolone (IVMP) were also administered once a week for 12 weeks (six pulses of 830 mg followed by six more pulses of 415 mg with a cumulative dose 7.5 g) from January to March 2015. Six weeks after completing corticosteroid treatment, the patient was re-examined, GO resulted inactive (CAS 2/10). Monthly follow-up showed progressive improvement of both inflammatory manifestations and eye motility. Euthyroidim was maintained, under escalating MMI dose which was discontinued on September 2015.GO persisted inactive, with only inconstant diplopia, a CAS of 1/10 and a severity NOSPECS score 2A3A405060GO. The patient could eventually resume her daily activities, including bicycle riding (February 2016). The patient remained euthyroid during the remaining follow-up (TSH 2.86 uUI/ml and undetectable TRAb on January 2018). Thyroid hemiagenesis is rare, with a prevalence estimated to 0.2% at systematic ultrasound screening [2]. Its association with Graves’ disease is exceptional and only 21 patients have been previously reported in the literature [3]. Interestingly, spontaneous conversion from hyperthyroidism to hypothyroidism or long-term remission has been previously reported in two cases. A third case, unresponsive to oral steroids underwent orbital decompression. Notably, the present report illustrates the second documented case of GO successfully treated with IVMP administration in thyroid hemiagenesis. * Giuseppe Costante giuseppe.costante@bordet.be