Accelerated male-pattern hair loss on Testosterone Cypionate: Week-by-Week Timeline of What to Expect

What the Depo-Testosterone label actually says

Under skin and appendages, the label's adverse reactions section lists male pattern of baldness next to hirsutism, seborrhea and acne among reactions reported in men given some androgens, without saying how often it occurs or when it begins [1]. The labeled dose is 50 to 400 mg intramuscularly every 2 to 4 weeks, given deep in the gluteal muscle [1].

How testosterone is linked to pattern hair loss

Cypionate is an oil-soluble testosterone ester absorbed slowly from the injection depot, with a half-life of about 8 days after intramuscular injection [1]. Testosterone can be converted to DHT, which contributes to male-pattern hair loss [2]; up to 10% of the body's testosterone is converted to DHT [2]. Excess DHT miniaturizes hair follicles, shortening the growth phase and lengthening the resting phase [2], and androgenetic alopecia is progressive, tending to worsen with time [4].

The closest thing to a timeline

The label gives no onset timing for hair loss [1]. The nearest published timing statement comes from a review of testosterone therapy in transgender men, which lists alopecia among the undesired effects and notes that most effects appear within several months while alopecia continues to develop after 1 year [3]. That review also describes a shortage of randomized trials and few long-term prospective studies in that population [3]. That review covers a different group from men treated with replacement doses for hypogonadism.

Treatments tested in randomized trials

A meta-analysis of randomized trials in men with androgenetic alopecia found 5% minoxidil, 1 mg finasteride and low-level laser therapy each superior to placebo for hair density, thickness or growth (P<0.00001) [5].

In a 24-week phase III trial, 458 men were randomized and 446 were evaluated for safety; target-area hair count increased by 20.2 hairs with a topical finasteride spray versus 6.7 with placebo (P<0.001), numerically similar to oral finasteride, while mean serum DHT fell 34.5% with topical and 55.6% with oral finasteride [6].

Dutasteride inhibits both type 1 and type 2 5-alpha reductase [7]. A review of randomized trials found dutasteride effective in androgenetic alopecia and better than finasteride in most of those studies; the review names finasteride and minoxidil as the only approved drugs for androgenetic alopecia [7].

Scalp dermoscopy is used routinely to stage the severity of androgenetic alopecia and to monitor progress and response to treatment over time [4].