### PTH Gene Overview

**Gene Symbol:** PTH  
**Gene Location:** Chromosome 11 (11p15.5)  
**Protein Product:** Parathyroid Hormone (PTH)

The PTH gene encodes the parathyroid hormone, a critical regulator of calcium and phosphate metabolism in the body. PTH acts on bones, kidneys, and the gastrointestinal tract to maintain calcium homeostasis. 

### 1. Associated Genes

While the summaries provided focus on the PTH gene itself, it is associated with several key genes and pathways, particularly in the context of calcium and phosphate regulation:

- **CALCR** (Calcitonin Receptor): Involved in the physiological response to calcitonin, counteracting the effects of PTH.
- **PTHLH** (Parathyroid Hormone-Like Hormone): Shares homology with PTH and is implicated in development and bone metabolism.
- **SOST** (Sclerostin): A protein that inhibits bone formation and is regulated by PTH.
- **FGF23** (Fibroblast Growth Factor 23): A hormone that regulates phosphate homeostasis and is involved in interactions with PTH.

### 2. Aging and Age-Related Diseases

PTH levels and function may change with aging, impacting age-related diseases:

- **Osteoporosis**: Age-associated declines in kidney function and changes in PTH signaling can lead to bone density loss and increase fracture risk.
- **Chronic Kidney Disease**: Aging is associated with a higher prevalence of kidney disease, which affects calcium and phosphate metabolism influenced by PTH. Secondary hyperparathyroidism can occur in the context of renal function decline.
- **Hyperparathyroidism**: Primary (due to adenomas) or secondary (in the context of chronic renal failure), which are more pronounced with aging, can lead to various comorbidities, including cardiovascular issues.

### 3. Drugs and Drug Classes Interacting with PTH

Several drugs and classes are known to interact with the PTH pathway:

- **Calcimimetics (e.g., Cinacalcet)**: Used to lower PTH levels in patients with secondary hyperparathyroidism.
- **Bisphosphonates**: Target high bone turnover states as a result of PTH dysregulation in osteoporosis and hypercalcemia.
- **PTH Analogues (e.g., Teriparatide)**: Used therapeutically in osteoporosis; mimics the anabolic effects of PTH on bone.
- **Vitamin D Analogs**: Used to manage conditions affected by calcium and phosphate metabolism, often in conjunction with PTH levels.

### 4. Pathways and Biological Processes

PTH is involved in several significant biological processes and signaling pathways:

- **Calcium Ion Homeostasis**: Critical in regulating plasma calcium levels by influencing intestinal absorption and renal excretion.
- **Bone Remodeling**: Stimulates osteoclastic activity to release calcium from bones.
- **Renin-Angiotensin System**: Indirect interaction via affecting renal function and blood pressure—potentially modulating PTH levels.
- **Phosphate Homeostasis**: Regulates phosphate reabsorption in the kidneys, balancing blood phosphate levels.
- **Wnt Signaling Pathway**: Involved in using PTH to regulate osteoblast function and bone remodeling.

In summary, the PTH gene plays a pivotal role in calcium and phosphate metabolism, with implications for various age-related diseases and therapeutic targets. Its interactions with other genes and pathways underscore its significance in bone health and metabolic regulation.