Why “physiologic range” is misleading

• In women, only about 20% of biologically active testosterone comes from circulating serum testosterone; roughly 80% is made locally inside tissues from adrenal precursors (DHEA, DHEAS, androstenedione) via intracrinology.​
• With age, both ovarian and adrenal androgens fall markedly, so women lose not only serum testosterone, but also the precursor pool that feeds local tissue production.​
• Because serum testosterone reflects only a fraction of total androgen activity, serum levels correlate poorly with symptoms or tissue exposure and are a weak guide for diagnosis or dosing.​

What “replacement” really means

• True replacement has to cover two losses:
  1. the modest serum testosterone normally present, and
  2. the much larger intracrine contribution from adrenal precursors that has disappeared.​
• To accomplish both, exogenous testosterone must be given at pharmacologic doses (by conventional lab standards) so that enough hormone reaches androgen receptors in tissues despite the absent precursor input.​
• In this context, “physiologic” refers to restoring tissue-level androgen action and clinical wellbeing, not keeping serum levels within premenopausal lab-reference ranges.​

Why serum levels on therapy are higher

• With pellet therapy, average doses in routine practice are around 150–250 mg per insertion, often weight‑adjusted, producing peak serum levels several-fold above endogenous female ranges and trough levels still higher than “normal.”​
• Even at these “supraphysiologic” serum levels, what is being replaced is the combined effect of serum testosterone plus the lost intracrine production that used to come from DHEA/DHEAS and androstenedione.​
• Clinical data show dose–response benefits (symptom relief, function, QoL) at these higher ranges, with a wide safety margin and no evidence that keeping serum within endogenous female limits is necessary or helpful.​

Practical dosing principle in lay terms

• Start with a dose high enough (often in the 100–200+ mg pellet range) to clearly relieve androgen‑deficiency symptoms, understanding that resulting blood levels will read “high” compared with standard female reference ranges.​
• Adjust dose and interval based on benefits versus androgenic side effects (acne, facial hair, etc.), rather than chasing a lab number, since a single serum value is highly variable and captures only about one‑fifth of total androgen activity.​
• The therapeutic target is adequate tissue androgen exposure—replacing the small serum component and the much larger lost adrenal‑intracrine contribution—not a “normal” lab report.​

Role of aromatization and “over‑aromatization”

• Testosterone is a precursor to estradiol via aromatase; local aromatization in breast and other tissues is the main postmenopausal source of estrogen.​
• When aromatase is upregulated (obesity, xenoestrogens, fibroids, endometriosis, endometrial and breast cancers), excess intracellular estradiol can overwhelm testosterone’s protective effect and stimulate breast and uterine tissues, promoting conditions such as breast cancer.​
• This is why combining testosterone with an aromatase inhibitor in high‑risk women or breast cancer patients preserves the beneficial androgen effect while preventing “over‑aromatization” to estradiol that could stimulate estrogen‑sensitive tumors.

Summary

• Dosing must be pharmacologic, because the goal is to replace both the relatively small circulating testosterone fraction and the larger intracrine androgen pool derived from adrenal precursors that declines with age.
• Clinical response and adverse‑effect profile should drive dose titration; serum testosterone is a poor surrogate for tissue exposure and should not be used as the primary dosing target.
• Initial implant doses are typically weight‑based and age-based (commonly in the ~150–250+ mg range for many women) with reinsertion at symptom recurrence, often at 3-month intervals, then individualized.
• Supraphysiologic serum concentrations relative to conventional female reference ranges are expected and necessary for adequate tissue androgenization and do not imply overtreatment.
• In women with estrogen‑sensitive conditions or elevated breast‑cancer risk, testosterone is ideally combined with an aromatase inhibitor in the implant to maintain androgenic/breast‑protective effects while preventing excess estradiol generation.