age-related loss of muscle mass and strength is called
Sarcopenia Sarcopenia is the degenerative loss of skeletal muscle mass (0.5–1% loss per year after the age of 50), quality, and strength associated with aging.[1] Sarcopenia is a component of the frailty syndrome. It is often a component of cachexia. It can also exist independently of cachexia; whereas cachexia includes malaise and is secondary to an underlying pathosis (such as cancer), sarcopenia may occur in healthy people and does not necessarily include malaise. The term is from Greek σάρξ sarx, "flesh" and πενία penia, "poverty".
Thymus The thymus enlarges during childhood, and atrophies at puberty. Unlike many other organs, the thymus is at its largest in childhood. The thymus reaches maximum weight (20 to 37 grams) by the time of puberty. The thymus of older people is scarcely distinguishable from surrounding fatty tissue. With aging the thymus slowly shrinks, eventually degenerating into tiny islands of fatty tissue. By the age of 75 years, the thymus weighs only 6 grams. In children the thymus is grayish-pink in colour and in adults it is yellow.