Recombinant growth hormone improves growth and adult height in patients with maternal inactivating GNAS mutations.

BACKGROUND: Maternal inactivating GNAS mutations lead to pseudohypoparathyroidism 1A (PHP1A), newly classified as inactivating parathyroid hormone (PTH)/PTHrP-signaling disorder type 2 of maternal inheritance (iPPSD2). Patients present with resistance to PTH and other hormones, subcutaneous ossifications, brachydactyly, short stature, and early-onset obesity. They can be born small for gestational age (SGA) and may present with growth hormone (GH) deficiency. The use of recombinant human GH (rhGH) therapy has been sporadically reported, yet we lack data on the long-term efficacy and safety of rhGH, as well as on adult height. OBJECTIVE: Our multicenter, retrospective, observational study describes growth in patients treated with rhGH in comparison with untreated iPPSD2/PHP1A controls. METHODS: We included 190 patients, of whom 26 received rhGH. Height, weight, body mass index at various time points, and adult height were documented. We analyzed the effect of rhGH on adult height by using linear mixed models. RESULTS: Adult height was available for 11/26 rhGH-treated individuals and for 69/164 controls. Patients treated with rhGH showed a gain in height of 0.7 standard deviation scores (SDS) after 1 year (CI +0.5 to +0.8, P < .001) and of 1.5 SDS after 3 years (CI +1.0 to +2.0, P < .001). Additionally, there was a clear beneficial impact of rhGH on adult height when compared with untreated controls, with a difference of 1.9 SDS (CI +1.1 to +2.7, P < .001). Body mass index SDS did not vary significantly upon rhGH therapy. CONCLUSION: Recombinant human growth hormone treatment of iPPSD2/PHP1A patients with short stature improves growth and adult height. More studies are needed to confirm long-term efficacy and safety.

Identification of Resistance to Exogenous Thyroxine in Humans.

Background: Thyroxine (T4) to triiodothyronine (T3) deiodination in the hypothalamus/pituitary is mediated by deiodinase type-2 (D2) activity. Dio2(-/-) mice show central resistance to exogenous T4. Patients with resistance to exogenous thyroxine (RETH) have not been described. The aim of this study was to identify hypothyroid patients with thyrotropin (TSH) unresponsiveness to levothyroxine (LT4) and to characterize the clinical, hormonal, and genetic features of human RETH. Methods: We investigated hypothyroid patients with elevated TSH under LT4 treatment at doses leading to clinical and/or biochemical hyperthyroidism. TSH and free T4 (fT4) were determined by chemiluminescence, and total T4, T3, and reverse T3 (rT3) by radioimmunoassay. TSH/fT4 ratio at inclusion and T3/T4, rT3/T4, and T3/rT3 ratios at follow-up were compared with those from patients with resistance to thyroid hormone (RTH) due to thyroid hormone receptor-ß (THRB) mutations. DIO2, including the Ala92-D2 polymorphism, selenocysteine binding protein 2 (SECISBP2), and THRB were fully sequenced. Results: Eighteen hypothyroid patients (nine of each sex, 3-59 years) treated with LT4 showed elevated TSH (15.5 ± 4.7 mU/L; reference range [RR]: 0.4-4.5), fT4 (20.8 ± 2.4 pM; RR: 9-20.6), and TSH/fT4 ratio (0.74 ± 0.25; RR: 0.03-0.13). Despite increasing LT4 doses from 1.7 ± 1.0 to 2.4 ± 1.7 µg/kg/day, TSH remained elevated (6.9 ± 2.7 mU/L). Due to hyperthyroid symptoms, LT4 doses were reduced, and TSH increased again to 7.9 ± 3.2 mU/L. In the euthyroid/hyperthyrotropinemic state, T3/T4 and T3/rT3 ratios were decreased (9.2 ± 2.4, RR: 11.3-15.3 and 2.5 ± 1.4, RR: 7.5-8.5, respectively) whereas rT3/T4 was increased (0.6 ± 0.2; RR: 0.43-0.49), suggesting reduced T4 to T3 and increased T4 to rT3 conversion. These ratios were serum T4-independent and were not observed in RTH patients. Genetic testing was normal. The Ala92-D2 polymorphism was present in 7 of 18 patients, but the allele dose did not correlate with RETH. Conclusions: Human RETH is characterized by iatrogenic thyrotoxicosis and elevated TSH/fT4 ratio. In the euthyroid/hyperthyrotropinemic state, it is confirmed by decreased T3/T4 and T3/rT3 ratios, and elevated rT3/T4 ratio. This phenotype may guide clinicians to consider combined T4+T3 therapy in a targeted fashion. The absence of germline DIO2 mutations suggests that aberrant post-translational D2 modifications in pituitary/hypothalamus or defects in other genes regulating the T4 to T3 conversion pathway could be involved in RETH.

Identification of four novel mutations in the thyroid hormone receptor-ß gene in 164 Spanish and 2 Greek patients with resistance to thyroid hormone.

OBJECTIVE: The aim of the study was to describe the clinical, biochemical, and genetic features of a sample of Mediterranean patients with RTH (resistance to thyroid hormone) due to mutations in TRß (thyroid hormone receptor beta) referred to our institution during the last 15 years. DESIGN: 166 blood samples were received for RTH genetic testing between January 1997 and December 2011. Genetic testing was performed by PCR amplification followed by sequencing of exons 7, 8, 9, and 10. Clinical and biochemical features were obtained from available information sent by referring hospitals. RESULTS: Mutations were identified in 50 patients (29 probands and 21 relatives). 64% were women, and mean ± stdev age at diagnosis among probands was 33.2 ± 20.5 years. The following clinical features were recorded: goiter in 50%, hyperkinetic behavior in 32%, and tachycardia in 29%. Up to 19% of the probands had undergone some type of thyroidal ablative therapy before diagnosis. As for biochemical features, mean ± stdev TSH was 10.2 ± 21.4 mUI/L, and mean ± stdev fT4 was 35.5 ± 10.8 pmol/L. We found four new mutations: p.Phe451Leu, p.Pro452Arg, p.Glu457Gly, and p.Phe459Leu. CONCLUSIONS: The clinical and biochemical characteristics of our samples of Mediterranean populations with RTH were similar to those described in the published literature. Interestingly, in our populations we have identified four novel mutations in the TRß gene.