The loss of hair in male balding is the result of a gradual reduction in the duration of anagen and a prolongation of the latent period of the hair cycle, and miniaturization of terminal hair follicles.
Testosterone belongs to male sex hormone androgen predominantly circulating in the bloodstream, and is maximally activated and converted to dihydrotestosterone (DHT) by the enzyme 5α-reductase. As you have mentioned, the physiological significance of DHT as an etiologic factor to induce male pattern hair loss (MPHL) has been revealed by the absence of this condition in men with a congenital disorder due to the deficiency of type 2 5α-reductase. That is why it is less likely that MPHL or hair follicle miniaturization contributes to the preserving energy for other organ systems.
That hypothesis seems unlikely to me given that, if the hypothesis were true, it would imply men with androgenic alopecia are in better health than men without. I did not learn of such an association in medical school.
Dear Hassan thanks for sharing us opinion, medical school not usually learn us everything that's because it hasn't every informations so proposal for new research are pushing medicine forward. Elderly are usually whom suffering from androgenetic alopecia so that's might keep some energy for them. It is just a proposal no available evidence for the time being.
I agree with you that male baldness is a part of aging process but am not with you in a defense mechanism, what I meant by energy preservation as compared with lactating women when diffuse hair loss happen during the period of breast feeding preserving energy and nutrients for milk production.