Understanding Your Hormones

How Your Hormones Connect

Your hormones are not isolated systems. Testosterone, estrogen, thyroid, cortisol, and insulin form a feedback network where a shift in one changes the others. A man with low testosterone may actually have a thyroid problem suppressing his HPG axis. A woman with irregular cycles may trace the issue back to insulin resistance raising her androgens. The body does not care about the label on the lab order. It runs on signals, and those signals cross boundaries.[1]

This guide maps the five major hormone systems, shows you what to test, and explains how to read the numbers that matter. If you are on TRT, HRT, or considering either, the protocol and monitoring sections give you the specifics. If you just want to understand why you feel the way you do, start with the blood work.

Testosterone & Estrogen

Testosterone and estrogen are not male and female hormones. Both sexes produce both. The ratio matters, the free fraction matters, and the binding proteins that sit between production and action matter. Four markers tell you most of what you need to know.[2] For the scientific foundation, start with testosterone basics. For a quick printable reference, see the lab marker cheat sheet. For the full guide to interpreting results, read how to read TRT labs.

Total testosterone is the headline number, but free testosterone is what your tissues actually use. You can have a solid total T and still feel terrible if most of it is bound to SHBG. High SHBG (common with aging, liver conditions, and certain medications) locks testosterone away. Low SHBG (common with insulin resistance and obesity) lets testosterone clear the body faster, which means more frequent dosing and greater estradiol conversion.[3] Our article on low SHBG covers this in detail.

Estradiol is not the enemy. Men need it for bone density, cardiovascular health, brain function, and libido. The goal is balance, not elimination. Crashing E2 with an aromatase inhibitor is often worse than running slightly high. Read the estradiol management guide for the full decision tree.

Thyroid

Your thyroid gland sets the metabolic rate for every cell in your body. When thyroid output drops, everything slows: energy, digestion, heart rate, body temperature, and the rate at which you clear and produce other hormones. Hypothyroidism and low testosterone share so many symptoms (fatigue, weight gain, brain fog, low libido) that one is frequently mistaken for the other.[4]

TSH is the screening test, but it does not tell the whole story. A TSH of 3.5 is technically "normal" but may indicate suboptimal thyroid function, especially if Free T3 (the active hormone) is in the lower third of the range. Thyroid antibodies (TPO, TgAb) should be checked at least once to rule out autoimmune thyroiditis, which affects roughly 10% of the population and is the most common cause of hypothyroidism.[5]

Cortisol & the HPA Axis

Cortisol is produced by your adrenal glands through a signaling chain called the HPA (hypothalamic-pituitary-adrenal) axis. In a healthy body, cortisol peaks within 30 minutes of waking, declines through the afternoon, and reaches its lowest point around midnight. This rhythm drives your energy, immune response, blood sugar regulation, and sleep onset.[6]

Chronic stress breaks this rhythm. Cortisol stays elevated into the evening, suppresses melatonin, fragments sleep, and directly lowers testosterone production. The HPA axis and the HPG axis (which governs testosterone and estrogen) compete for resources. When your body is in a sustained stress state, reproductive hormones take the hit first.[7]

Insulin & Metabolic Hormones

Insulin resistance is one of the most underappreciated drivers of hormonal dysfunction. When your cells stop responding efficiently to insulin, your pancreas produces more of it to compensate. Chronically elevated insulin lowers SHBG, which changes how testosterone is bound and cleared. It also promotes fat storage (especially visceral fat), and that fat tissue converts testosterone to estrogen through aromatase activity. The result is a self-reinforcing loop: more insulin resistance leads to worse hormone profiles, which leads to more fat gain, which worsens insulin resistance.[8]

This is why body composition changes on TRT often stall for men who have not addressed metabolic health. Adding testosterone to an insulin-resistant system is fighting against the current. Fixing fasting glucose, HbA1c, and insulin sensitivity often unlocks improvements that dose increases cannot. See our prediabetes action plan and A1c reduction guide for the protocols.

TRT & HRT Protocols

There is no single best protocol. The right approach depends on your SHBG level, how you metabolize testosterone, and what you can realistically stick with. That said, modern best practice has moved decisively toward more frequent, smaller doses. The old model of one large injection every two weeks produces peaks and valleys that most people experience as mood swings, energy crashes, and fluctuating libido.[9]

Typical starting doses range from 100 to 160 mg per week of testosterone cypionate. Adjustments are made based on lab results at the 6-8 week mark. Some men do well on 80 mg per week, others need 200 mg. The dose matters less than the outcome: where your blood levels land and how you feel. Supraphysiological doses (total T above 1,200 ng/dL) do not produce better results. They increase estradiol conversion, elevate hematocrit, and often cause the very symptoms men are trying to escape.

HCG (Human Chorionic Gonadotropin)

Exogenous testosterone shuts down your brain's signal to produce LH and FSH, which means your testes stop producing testosterone and sperm. HCG mimics LH and keeps the testes active. A typical dose is 250-500 IU, two to three times per week via subcutaneous injection. Beyond fertility preservation, HCG maintains intratesticular testosterone and downstream hormones like pregnenolone and DHEA. Read the full HCG guide for dosing details, and our DHEA and pregnenolone guide for adrenal support on TRT.

Aromatase Inhibitors

Aromatase converts testosterone to estradiol. When some providers see elevated E2, they prescribe anastrozole by default. The current consensus among experienced TRT practitioners is that AIs should be a last resort. Estradiol is essential (bones, brain, heart, libido). The better approach is to manage E2 through injection frequency (more frequent = less aromatization per dose), body fat reduction, and dose adjustment.[10] See the estradiol management guide for the decision tree.

Lab Panels & Testing

Lab work is the foundation of responsible hormone management. You should never start a protocol without baseline labs, and you should never continue one without regular monitoring. For a complete breakdown of when to draw blood and why timing matters, read the lab testing schedule and the optimal testing timing guide.

Risks & Red Flags

TRT and HRT are safe when properly prescribed and monitored, but they are not risk-free. Any provider who tells you there are zero downsides is not someone you should trust with your hormones.

Key Risks to Monitor

Hematocrit: TRT stimulates red blood cell production. When hematocrit rises above 52-54%, blood viscosity increases and so does cardiovascular risk. This is the most important safety marker on TRT. Regular CBC monitoring is non-negotiable. If hematocrit creeps above 52%, your provider may recommend therapeutic phlebotomy, dose reduction, or a shift to more frequent lower-volume injections.[11] Read the hematocrit guide for the full protocol.

Fertility: Exogenous testosterone suppresses the HPG axis, and sperm production drops significantly within weeks. For some men, sperm count reaches zero. Recovery after stopping TRT can take 6 to 18 months and is not guaranteed in every case.[12] If fertility is a concern, HCG should be part of your protocol from day one. Consider banking sperm before starting.

Cardiovascular: The TRAVERSE trial (2023, NEJM) found that TRT in men with hypogonadism did not increase the rate of major cardiovascular events compared to placebo.[13] That said, managing hematocrit, blood pressure, and lipids remains essential for anyone on long-term hormone therapy.

Finding the Right Provider

Not all doctors understand hormone optimization. If your provider dismisses symptoms because your total T is "within range," does not check free testosterone or estradiol, prescribes an AI by default, or offers a single large injection every two weeks, seek a specialist. Endocrinologists, urologists focused on male health, and telemedicine clinics specializing in hormone optimization are all options. The right provider works with you to find your optimal protocol based on labs and symptoms together.

References

1. Veldhuis JD, et al. "Endocrine control of body composition in infancy, childhood, and puberty." Endocrine Reviews. 2005;26(1):114-146.
2. Bhasin S, Brito JP, Cunningham GR, et al. "Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline." J Clin Endocrinol Metab. 2018;103(5):1715-1744. doi:10.1210/jc.2018-00229
3. Grossmann M, Matsumoto AM. "A Perspective on Middle-Aged and Older Men With Functional Hypogonadism: Focus on Holistic Management." J Clin Endocrinol Metab. 2017;102(3):1067-1075.
4. Krassas GE, et al. "Thyroid function and human reproductive health." Endocrine Reviews. 2010;31(5):702-755.
5. Garber JR, et al. "Clinical practice guidelines for hypothyroidism in adults." Thyroid. 2012;22(12):1200-1235.
6. Nicolaides NC, et al. "Stress, the stress system and the role of glucocorticoids." Neuroimmunomodulation. 2015;22(1-2):6-19.
7. Cumming DC, et al. "Reproductive hormone increases in response to acute exercise in men." Med Sci Sports Exerc. 1986;18(4):369-373.
8. Kelly DM, Jones TH. "Testosterone and obesity." Obes Rev. 2015;16(7):581-606.
9. Salter CA, Mulhall JP. "Guideline of Guidelines: Testosterone Therapy for Testosterone Deficiency." BJU Int. 2019;124(5):722-729.
10. Travison TG, Araujo AB, et al. "A Population-Level Decline in Serum Testosterone Levels in American Men." J Clin Endocrinol Metab. 2007;92(1):196-202.
11. Ohlander SJ, et al. "Erythrocytosis Following Testosterone Therapy." Sex Med Rev. 2018;6(1):77-85.
12. Patel AS, Leong JY, Ramasamy R. "Prediction of Male Infertility by the WHO Laboratory Manual." World J Mens Health. 2021;39(2):235-242.
13. Lincoff AM, Bhasin S, Flevaris P, et al. "Cardiovascular Safety of Testosterone-Replacement Therapy." N Engl J Med. 2023;389(2):107-117. (TRAVERSE trial)