Multiple endocrine neoplasia type 2 (MEN 2) comprises a heterogeneous group of neoplasic disorders that most commonly have a single missense substitution of the RET protooncogene (RET) involving exons 10 and 11. It was previously reported a MEN 2A kindred in which the father presented with a rare phenotype consisting of bilateral ACTH-producing pheochromocytoma and medullary thyroid carcinoma. We recently performed mutational analysis of the father and his 4 children using a denaturing gradient gel electrophoresis approach and PCR-amplified genomic DNA, followed by direct sequencing or restriction fragment length polymorphism testing. All 4 children showed a RET sequence variation. The common exon 11 Cys(634)Arg RET mutation was present in 2 of the 4 children who had undergone thyroidectomy for C cell disease. The remaining 2 children, who did not harbor the Cys(634)Arg mutation and are negative for C cell and adrenal disease, carry a previously unreported Val(648)Ile missense change in RET exon 11. This novel substitution was not found in the unaffected mother or in 200 control alleles. Both RET variants were present in the father affected with MEN 2A and the unusual ACTH-producing pheochromocytoma. We speculate that the double RET mutation may have modified and contributed to the rare MEN 2A phenotype in the father.

Leydig cell hypoplasia (LCH) is characterized by a decreased response of the Leydig cells to LH. As a result, patients with this syndrome display aberrant male development ranging from complete pseudohermaphroditism to males with micropenis but with otherwise normal sex characteristics. We have evaluated three brothers with a mild form of LCH. Analysis of their LH receptor (LHR) gene revealed a homozygous missense mutation resulting in a substitution of a lysine residue for a isoleucine residue at position 625 of the receptor. In vitro analysis of this mutant LHR, LHR(I625K), in HEK293 cells indicated that the signaling efficiency was significantly impaired, which explains the partial phenotype. We have compared this mutant LHR to two other mutant LHRs, LHR(A593P) and LHR(S616Y), identified in a complete and partial LCH patient, respectively. Although the ligand-binding affinity for all three mutant receptors was normal, the hormonal response of LHR(A593P) was completely absent and that of LHR(S616Y) and LHR(I625K) was severely impaired. Low cell surface expression explained the reduced response of LHR(S616Y), while for LHR(I625K) this diminished response was due to a combination of low cell surface expression and decreased coupling efficiency. For LHR(A593P), the absence of a reduced response resulted from both poor cell surface expression and a complete deficiency in coupling. Our experiments further show a clear correlation between the severity of the clinical phenotype of patients and overall receptor signal capacity, which is a combination of cell surface expression and coupling efficiency.

Objective: To characterize clinically and hormonally the syndrome of autosomal recessive familial growth hormone deficiency (FGHD) recently identified in Itabaianinha, Sergipe, Brazil, caused by a novel mutation (mt) that inactivates the growth hormone-releasing hormone receptor (GHRH-R) gene. Design: Clinical and hormonal evaluations were performed in 21 FGHD individuals (mt/mt group) aged 8 to 63 years, 13 heterozygotes for the GHRH-R mutation (wt/mt group) and 5 homozygotes for the wild type (wt) allele (wt/wt group), identified by genotyping of peripheral blood leukocyte DNA. Methods: Clinical and hormonal characterization included physical examination and measurement of GH, IGF-I, IGF binding protein-3 (IGFBP-3), cortisol, prolactin, LH, FSH, and free thyroxine (FT4).Results: Clinical features were consistent with isolated growth hormone deficiency. Height was significantly reduced in the mt/mt group compared with the wt/mt group (mean height standard deviation score (SDS) Ϯ S.D.: ¹7.35 Ϯ 1.37 vs ¹1.84 Ϯ 1.44 respectively, P < 0.0001), and the wt/wt group (¹1.85 Ϯ 0.81, P ¼ 0.0007). The height of the 13 wt/mt subjects did not differ from the 5 wt/wt individuals. Serum GH, IGF-I, IGF-I SDS, IGFBP-3 and IGFBP-3 SDS were all significantly lower in the mt/mt group than in the wt/mt and wt/wt groups. Two affected children treated with GH for 1 year showed a normal growth response. Serum IGF-I and IGF-I SDS were lower in wt/mt compared with wt/wt group, but did not reach statistical significance. IGF-I and IGF-I SDS correlated inversely with age in wt/mt group. Conclusions: FGHD due to an autosomal recessive GHRH-R gene mutation leads to marked dwarfism, phenotypically and hormonally indistinguishable from other forms of isolated GH deficiency. Heterozygotes for the GHRH-R mutation appear to have a partial defect in the GH/IGF axis, with no apparent height impairment.

Background. The diagnosis of medullary thyroid carcinoma (MTC) depends on the calcitonin immunohistochemistry. Familial MTC is associated with C‐cell hyperplasia (CCH), whereas sporadic MTC is not. A specific and sensitive calcitonin immunohistochemistry is necessary for the diagnosis of MTC and CCH. Methods. An affinity‐purified anti‐calcitonin anti‐serum (APxCT) was used for immunohistochemistry of the thyroids of 15 patients with MTC. The thyroids of five patients with familial MTC were studied in detail, with each gland sectioned in 48 areas. Results. Between three and ten independent MTC were found in each thyroid, and CCH was found in all five patients (24.2%, varying from 8.4–56.3% of the 48 areas from each thyroid). MTC and CCH were localized mainly in the middle third and in the central axis of the thyroid lobes. They often were found together in the same area (in a total of 21 areas for the five thyroids sectioned in 48 areas) but ten areas with MTC did not have CCH, and 37 areas with CCH did not have MTC. In ten thyroids partially studied, CCH was indicated in three patients thought to have sporadic MTC. In two thyroids, with follicular and papillary carcinoma, a higher density of C‐cells was found around the tumors, but disease was not characterized as CCH. Conclusions. APxCT antiserum increased the immunohistochemical specificity and sensitivity. The distinction of the familial from the sporadic MTC requires a careful and extensive search of CCH. C‐cells in high density may be found around follicular cell carcinomas, being a potential source of diagnostic error.

INTRODUCTION:Medullary thyroid carcinoma may occur in a sporadic (s-medullary thyroid carcinoma, 75%) or in a multiple endocrine neoplasia type 2 form (MEN2, 25%). These clinical forms differ in many ways, as s-medullary thyroid carcinoma cases are RET-negative in the germline and are typically diagnosed later than medullary thyroid carcinoma in MEN2 patients. In this study, a set of cases with s-medullary thyroid carcinoma are documented and explored. PURPOSE: To document the phenotypes observed in s-medullary thyroid carcinoma cases from a university group and to attempt to improve earlier diagnosis of s-medullary thyroid carcinoma. Some procedures for diagnostics are also recommended. METHOD: Patients (n=26) with apparent s-medullary thyroid carcinoma were studied. Their clinical data were reviewed and peripheral blood was collected and screened for RET germline mutations. RESULTS:The average age at diagnosis was 43.9 years (± 10.82 SD) and did not differ between males and females. Calcitonin levels were increased in all cases. Three patients presented values that were 100-fold greater than the normal upper limit. Most (61.54%) had values that were 20-fold below this limit. Carcinoembryonic antigen levels were high in 70.6% of cases. There was no significant association between age at diagnosis, basal calcitonin levels or time of disease onset with thyroid tumor size (0.6-15 cm). Routine thyroid cytology yielded disappointing diagnostic accuracy (46.7%) in this set of cases. After total thyroidectomy associated with extensive cervical lymph node resection, calcitonin values remained lower than 5 pg/mL for at least 12 months in eight of the cases (30.8%). Immunocyto-and histochemistry for calcitonin were positive in all analyzed cases. None of the 26 cases presented germline mutations in the classical hotspots of the RET proto-oncogene. CONCLUSION: Our cases were identified late. The basal calcitonin measurements and immunostaining for calcitonin were highly useful for diagnosing s-medullary thyroid carcinoma. The rate of complete patient recovery was low, and none of the parameters analyzed were useful predictors of the thyroid tumor size. Our findings support previous recommendations for routine serum calcitonin evaluation and immunostaining analysis involving single thyroid nodules.