Autoimmunity: Certain autoimmune conditions can cause pernicious anemia
The magnitude varies based on lifestyle factors and individual biology
This hormonal cascade works as follows: The hypothalamus releases gonadotropin-releasing hormone (GnRH) GnRH signals the anterior pituitary to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH) LH stimulates the Leydig cells to produce testosterone Rising testosterone feeds back to the hypothalamus and pituitary to regulate production (negative feedback loop) Testosterone is responsible for: Muscle protein synthesis and lean body mass maintenance Bone mineral density Red blood cell production Libido and sexual function Energy, mood, and cognitive function Fat distribution and metabolic health Normal total testosterone in adult men ranges from approximately 300 to 1,000 ng/dL, with levels declining by roughly 1 to 2 percent per year after age 30 (Harman et al., 2001)

(A preliminary trial of CJC-1295 was halted early after a study volunteer died of a heart attack.) Healing and repair peptides They call it the Wolverine Stack: BPC-157 (Body Protection Compound-157) and TB-500 (Thymosin Beta-500)
DOI: 10.3390/molecules191119066
Derived from a segment of the HGH molecule, it is touted to promote lipolysis (fat breakdown) without affecting lean muscle mass