This review summarizes recent basic and clinical advances in cortisol-producing adrenal tumors, including Cushing’s syndrome (CS) and mild autonomous cortisol secretion (MACS). Recent clinical reports on the epidemiology and diagnostic challenges of CS and MACS are presented. The review highlights recent progress in understanding the molecular pathogenesis of adrenal cortisol-producing tumors. A major recent finding is the discovery of loss-of-function mutation in KDM1A as the underlying cause of the long-standing mystery of diet-dependent CS in primary bilateral macronodular adrenal hyperplasia (PBMAH). Furthermore, the recent clarification of the molecular basis of cortisol-producing adenomas (CPAs) has deepened our understanding of the functional differences in the autonomicity of CPAs between overt CS and MACS. These findings made us reconsider the categorization of adrenal tumors, including non-functioning adrenal tumors (NFATs). Finally, we reviewed the rarely discussed but critical condition of immune reconstitution inflammatory syndrome (IRIS) following CS treatment, including a case from our own experience. IRIS should be kept in mind when initiating treatment for CS patients with extremely high serum cortisol levels.

GPR75 has emerged as a therapeutic target for obesity following the discovery of a causal relationship between GPR75 variants and reduced body mass index in humans. Herein, we examined whether GPR75 is dispensable for normal feeding, body growth, and reproduction using newly generated Gpr75 knockout (KO) rats fed normal chow. Gpr75 was highly expressed in the brain, including several hypothalamic nuclei, in rats of both sexes. Gpr75 KO male and female rats exhibited significantly lower food intake, reduced feeding duration during the dark phase, and lower body weight (BW) than wild-type rats. Importantly, Gpr75 KO did not affect reproduction in either sex, including puberty onset, pulsatile luteinizing hormone secretion, or litter size. We also examined the effects of Gpr75 KO on hyperphagia, obesity, hyperglycemia, and hyperinsulinemia in male rats on a high-fat diet (HFD). HFD-fed Gpr75 KO male rats exhibited significantly lower food intake, BW, and fat accumulation than wild-type rats and were normoglycemic and normoinsulinemic. Notably, hypothalamic Ccl5 (encoding C-C motif chemokine ligand 5 [CCL5]) expression was significantly higher in Gpr75 KO male rats than in wild-type rats, suggesting that Gpr75 KO may prevent HFD-induced hyperphagia via central CCL5 signaling in rats. Thus, GPR75 signaling, although dispensable for reproduction, contributes to feeding and body growth in rats on normal chow and is involved in HFD-induced hyperphagia, obesity, hyperglycemia, and hyperinsulinemia development. Therefore, GPR75 antagonism may offer a potential therapeutic approach to control feeding and BW and prevent obesity and insulin resistance without affecting reproduction in humans.

This study aimed to clarify the expression levels of autophagy-related molecules, such as β-catenin, LC3B, and p62, in thyroid carcinoma (TC) cases of different histological types and clinicopathological characteristics. A total of 70 surgically resected thyroid nodules, including 43 papillary thyroid carcinoma (PTC), and other control groups such as five follicular adenoma (FA), five hyalinizing trabecular tumor (HTT), five follicular TC (FTC), six poorly differentiated TC (PDTC), and six anaplastic follicular cell-derived thyroid carcinoma (ATC), were analyzed by dual-color immunofluorescence for β-catenin, LC3B, and p62. Statistical analyses were used to determine the association of autophagy-related molecules with BRAF^V600E/TERT promoter mutations, Ki-67 labeling index, and clinicopathological characteristics. p62 immunoreactivity was most frequently observed in PTC, particularly in classical and tall cell subtypes. This protein appeared to co-localize with LC3B and β-catenin in intranuclear cytoplasmic inclusions (INIs) of PTC. Conversely, p62 expression was rarely observed in either FTC or PDTC. The expression levels of p62 and its co-localization with β-catenin and LC3B correlated significantly with the presence of the BRAF^V600E mutation. Frequent co-localization of dot-shaped perinuclear β-catenin signals with a component of the trans-Golgi apparatus in tall cell PTC subtype was also observed. This study revealed differences in the expression patterns of β-catenin, LC3B, and p62 among different TC types. Abnormal β-catenin expression may be linked to autophagy dysfunction, which triggers genomic instability and promotes tumor aggressiveness. These autophagy-related molecules may be cooperatively associated with INI formation during PTC carcinogenesis.

Hepatic carbohydrate and lipid metabolism is strictly regulated by hormones such as insulin, glucagon, cortisol, and adrenaline, dynamically adapting to diet and stress. Metabolic zonation, a key feature of liver function, has been studied for decades. It refers to the spatial arrangement of hepatocytes with distinct metabolic roles along the portal-to-central vein axis, shaped by nutrient and oxygen gradients, as well as signaling molecules. However, traditional methods have struggled to reveal the spatial regulation of gene expression and signaling within these zones. Recent advances in single-cell and spatial omics technologies now allow detailed analysis of gene expression, signaling pathways, and cell-cell interactions with spatial resolution, providing new insights beyond classical models. Metabolic zonation research is rapidly advancing, and the concept of immune zonation, describing the spatial distribution of immune cells, has gained attention for its role in liver metabolism. These findings have improved our understanding of metabolic changes in conditions like fatty liver disease and diabetes. However, many questions remain, including the dynamic effects of diet and hormones and disease-related alterations. This review summarizes past and recent findings on metabolic zonation, explores the role of immune zonation and hormonal regulation, and discusses the latest technologies and future challenges.

Hypercalcemia, a common electrolyte imbalance, requires accurate differential diagnosis to guide appropriate management. PTH-dependent hypercalcemia, predominantly caused by primary hyperparathyroidism (PHPT) and rarely by familial hypocalciuric hypercalcemia (FHH)—mainly due to heterozygous loss-of-function mutations in the CASR gene encoding the calcium-sensing receptor (CaSR)—now includes acquired hypocalciuric hypercalcemia (AHH) as an emerging disease entity. Initially identified as analogous to FHH, AHH was characterized by blocking antibodies targeting the CaSR. However, our research has identified unique autoantibodies, termed biased antibodies, that paradoxically regulate signaling by enhancing Gq activity while suppressing Gi activity. Investigating their mechanisms has not only provided insights into specific treatments for AHH but also suggested novel activation mechanisms and binding sites of the CaSR, offering a fresh perspective on the regulation of PTH secretion. In clinical practice, recognizing AHH is crucial. A key diagnostic feature is fluctuating serum calcium levels, making a wait-and-see approach viable for mild hypercalcemia. Conversely, hypercalcemic crises necessitate immediate diagnostic and therapeutic interventions. The most important diagnostic clue to differentiate AHH from PHPT is hypermagnesemia. Additionally, AHH is less likely to involve AVP resistance (i.e., nephrogenic diabetes insipidus) and acute kidney injury (AKI), owing to preserved medullary hyperosmolarity and minimal interference with AVP signaling. Finally, a relatively low PTH level serves as another distinguishing feature. Based on these observations, we propose a novel diagnostic guide for PTH-dependent hypercalcemia. We anticipate that this guide will help identify previously undiagnosed AHH cases in routine practice, enabling timely and effective management of this rare condition.