A Patient with speechlessness and rhabdomyolysis: a rare presentation of severe hypocalcaemia.

A 29-year-old man with no medical history presented to our emergency department with episodes of sudden speechlessness, hoarseness, vomiting after drinking cold water and spasms of his hands. Chvostek's and Trousseau's signs were both seen at presentation. Blood tests revealed severe hypocalcaemia (1.03 mmol/L) and rhabdomyolysis (creatine kinase (CK) of 2962 IU/L). The patient was treated immediately with calcium intravenously with an almost immediate improvement of his voice and quick normalisation of his CK. Additional investigation showed primary hypoparathyroidism in the presence of a vitamin D deficiency, requiring lifelong treatment with calcium supplements and alphacalcidol. Severe hypocalcaemia can be life threatening and prompt treatment is essential. This case reports the unusual first presentation of hypocalcaemia via speechlessness and vomiting together with rhabdomyolysis. Identifying an atypical presentation of hypocalcaemia is critical, for it can be lifesaving.

Thyrostimulin Regulates Osteoblastic Bone Formation During Early Skeletal Development.

The ancestral glycoprotein hormone thyrostimulin is a heterodimer of unique glycoprotein hormone subunit alpha (GPA)2 and glycoprotein hormone subunit beta (GPB)5 subunits with high affinity for the TSH receptor. Transgenic overexpression of GPB5 in mice results in cranial abnormalities, but the role of thyrostimulin in bone remains unknown. We hypothesized that thyrostimulin exerts paracrine actions in bone and determined: 1) GPA2 and GPB5 expression in osteoblasts and osteoclasts, 2) the skeletal consequences of thyrostimulin deficiency in GPB5 knockout (KO) mice, and 3) osteoblast and osteoclast responses to thyrostimulin treatment. Gpa2 and Gpb5 expression was identified in the newborn skeleton but declined rapidly thereafter. GPA2 and GPB5 mRNAs were also expressed in primary osteoblasts and osteoclasts at varying concentrations. Juvenile thyrostimulin-deficient mice had increased bone volume and mineralization as a result of increased osteoblastic bone formation. However, thyrostimulin failed to induce a canonical cAMP response or activate the noncanonical Akt, ERK, or mitogen-activated protein kinase (P38) signaling pathways in primary calvarial or bone marrow stromal cell-derived osteoblasts. Furthermore, thyrostimulin did not directly inhibit osteoblast proliferation, differentiation or mineralization in vitro. These studies identify thyrostimulin as a negative but indirect regulator of osteoblastic bone formation during skeletal development.

Thyrostimulin deficiency does not alter peripheral responses to acute inflammation-induced nonthyroidal illness.

Thyrostimulin, a putative glycoprotein hormone, comprises the subunits GPA2 and GPB5 and activates the TSH receptor (TSHR). The observation that proinflammatory cytokines stimulate GPB5 transcription suggested a role for thyrostimulin in the pathogenesis of nonthyroidal illness syndrome (NTIS). In the present study, we induced acute inflammation by LPS administration to GPB5(-/-) and WT mice to evaluate the role of thyrostimulin in peripheral thyroid hormone metabolism during NTIS. In addition to serum thyroid hormone concentrations, we studied mRNA expression and activity of deiodinase types I, II, and III (D1, D2, and D3) in peripheral T3 target tissues, including liver, muscle, and white and brown adipose tissue (WAT and BAT), of which the latter three express the TSHR. LPS decreased serum free (f)T4 and fT3 indexes to a similar extent in GPB5(-/-) and WT mice. Serum reverse (r)T3 did not change following LPS administration. LPS also induced significant alterations in tissue D1, D2, and D3 mRNA and activity levels, but only the LPS-induced increase in WAT D2 mRNA expression differed between GPB5(-/-) and WT mice. In conclusion, lacking GPB5 during acute illness does not affect the LPS-induced decrease of serum thyroid hormones while resulting in subtle changes in tissue D2 expression that are unlikely to be mediated via the TSHR.

Complete inhibition of rhTSH-, Graves' disease IgG-, and M22-induced cAMP production in differentiated orbital fibroblasts by a low-molecular-weight TSHR antagonist.

The TSH receptor (TSHR) on orbital fibroblasts (OF) is a proposed target of the autoimmune attack in Graves' ophthalmopathy. In the present study, we tested whether the novel low-molecular-weight (LMW) TSHR antagonist Org-274179-0 inhibits cAMP production induced by rhTSH, Graves' disease IgG (GD-IgG), or M22 (a potent human monoclonal TSHR stimulating antibody) in cultured and differentiated OF from Graves' ophthalmopathy patients. cAMP production significantly increased after incubation either with 10 mU/ml rhTSH (3-fold; P ≤ 0.05), 1 mg/ml GD-IgG (2-fold; P ≤ 0.05), or 500 ng/ml M22 (5-fold; P ≤ 0.05). Incubation with the LMW TSHR antagonist dose dependently inhibited rhTSH, GD-IgG as well as the M22-induced cAMP production at nanomolar concentrations; complete blockade was affected at 10(-6) M. Our results suggest that GD-IgG- and M22-induced cAMP production in differentiated OF is exclusively mediated via the TSHR because it can be completely blocked by the LMW TSHR antagonist, Org 274179-0.

Thyrotropin receptor-stimulating Graves' disease immunoglobulins induce hyaluronan synthesis by differentiated orbital fibroblasts from patients with Graves' ophthalmopathy not only via cyclic adenosine monophosphate signaling pathways.

BACKGROUND: Both expression of the thyrotropin receptor (TSHR) and the production of hyaluronan (HA) by orbital fibroblasts (OF) have been proposed to be implicated in the pathogenesis of Graves' ophthalmopathy (GO). HA is synthesized by three types of HA synthase. We hypothesized that TSHR activation by recombinant human TSH (rhTSH) and TSHR-stimulating Graves' disease immunoglobulins (GD-IgGs) via induced cyclic adenosine monophosphate (cAMP) signaling increases HA synthesis in differentiated OF from GO patients. METHODS: Cultured human OF, obtained during decompression surgery from 17 patients with severe GO, were stimulated in vitro to differentiate into adipocytes. Differentiation was evaluated by phase-contrast microscopy. The differentiated OF were stimulated by rhTSH or by TSHR-stimulating GD-IgG. We measured cAMP using a biochemical assay, HA synthase mRNA expression by quantitative polymerase chain reaction, and HA in the supernatant by enzyme-linked immunosorbent assay. RESULTS: All differentiated OF cultures expressed higher levels of TSHR mRNA than nondifferentiated OF cultures. Stimulation by rhTSH induced a marked cAMP response in 11 of 12 differentiated OF cultures, but no measurable HA response in all but one differentiated OF cultures. By contrast, stimulation by GD-IgG induced a moderate cAMP response in a number of differentiated OF cultures, but a marked HA response in the majority of differentiated OF cultures. CONCLUSION: Stimulation of differentiated OF by GD-IgG, but not by rhTSH, induces HA synthesis in the majority of patients, suggesting that in most patients TSHR-mediated cAMP signaling does not play a pivotal role in GD-IgG-induced HA synthesis in differentiated OF cultures.

Effects of thyrotropin and thyrotropin-receptor-stimulating Graves' disease immunoglobulin G on cyclic adenosine monophosphate and hyaluronan production in nondifferentiated orbital fibroblasts of Graves' ophthalmopathy patients.

BACKGROUND: Orbital fibroblasts are involved in the pathogenesis of Graves' ophthalmopathy (GO) by producing hyaluronan (HA), synthesized by three types of hyaluronan synthases (HAS1, HAS2, and HAS3). Thyrotropin receptors (TSHR) expressed in orbital fibroblasts activate the cyclic adenosine monophosphate (cAMP) pathway. Only sparse data are available at present supporting a role for TSHR activation in the regulation of HA in GO orbital fibroblasts. We hypothesize that TSHR activation, via cAMP signaling, results in induction of HAS1-3 mRNA expression and HA production by nondifferentiated GO orbital fibroblasts. METHODS: Cultured nondifferentiated orbital fibroblasts obtained during orbital decompression surgery from 15 GO patients were stimulated with recombinant human TSH (rhTSH), TSHR-stimulating Graves' disease immunoglobulin G (GD-IgG) or forskolin (FSK), or interleukin-1beta (IL-1beta). RESULTS: FSK significantly stimulated cAMP production, HAS1 and HAS3 mRNA expression, and HA secretion in orbital fibroblasts. IL-1beta slightly induced cAMP production, but induced HAS mRNA expression of all three isoforms and HA secretion. In contrast, the effects of rhTSH and GD-IgG on cAMP were modest and absent, respectively, and on HAS mRNA and HA synthesis were completely absent. CONCLUSIONS: The strong increase in cAMP synthesis by FSK in nondifferentiated GO orbital fibroblasts results in increased HA synthesis, but TSHR activation by rhTSH or GD-IgG does not result in altered HA synthesis. Our results do not support a predominant role for GD-IgGs in the accumulation of orbital glycosaminoglycans; cytokines like IL-1beta seem largely responsible for excessive glycosaminoglycan production by nondifferentiated orbital fibroblasts in early immunopathogenesis of GO.

Transient hypothyroxinemia in juvenile glycoprotein hormone subunit B5 knock-out mice.

The heterodimer thyrostimulin, comprised of two novel glycoprotein hormone subunits GPA2 and GPB5, activates the TSH receptor. To understand its role in the regulation of the hypothalamus-pituitary-thyroid (HPT-) axis, we evaluated juvenile and adult GPB5 knock-out (GPB5(-/-)) and wild type mice (WT) during euthyroidism, hypothyroidism and thyrotoxicosis. Surprisingly, juvenile euthyroid GPB5(-/-) mice displayed marked hypothyroxinemia (25% lower serum T(4), unchanged TSH) and also during thyrotoxicosis juvenile GPB5(-/-) mice had 25% lower serum T(4), compared to WT. During hypothyroidism, despite similar serum T(4), pituitary TSHbeta mRNA was 2-fold lower in GPB5(-/-) mice compared to WT. Adult mice displayed increased pituitary deiodinase type 2 during euthyroidism and decreased serum T(4) during hypothyroidism in GPB5(-/-). Thus, lacking GPB5 results in moderate deviations of the HPT-axis. The more pronounced differences observed in juvenile mice compared to adult mice are in agreement with the notion that GPB5 has a role during development.