Secondary Hypogonadism: History of Treatment Over Decades

What Is Secondary Hypogonadism and Why Its Treatment History Matters

Secondary hypogonadism arises when the hypothalamus fails to release adequate gonadotropin-releasing hormone (GnRH), or the pituitary fails to secrete sufficient luteinizing hormone (LH) and follicle-stimulating hormone (FSH), leaving otherwise healthy testes without adequate stimulation. This distinguishes it sharply from primary (testicular) hypogonadism.

Tracking the treatment timeline matters clinically because therapy choices still depend on whether a patient wants fertility preserved. A man given testosterone replacement therapy will suppress endogenous LH and FSH, often rendering him azoospermic. Understanding why each treatment emerged, and what gap it was designed to fill, guides today's shared decision-making.

The 2018 Endocrine Society Clinical Practice Guideline on male hypogonadism states directly: "We suggest against starting testosterone therapy in patients who are actively trying to conceive" and recommends gonadotropin or GnRH therapy instead when fertility is desired [1].

Distinguishing Primary from Secondary: A Diagnostic Prerequisite

Before any treatment history makes sense, clinicians must confirm the subtype. Serum total testosterone below 300 ng/dL (10.4 nmol/L) on two morning samples, paired with low or inappropriately normal LH and FSH, establishes the secondary pattern [1]. Primary hypogonadism produces high gonadotropins; secondary does not.

This diagnostic distinction only became routine once reliable gonadotropin assays were available in the 1960s, which is partly why early testosterone therapy was applied to both subtypes indiscriminately.

The 1930s and 1940s: First Testosterone Extracts

The first successful isolation of testosterone occurred in 1935 when Ernst Laqueur's group in Amsterdam crystallized the hormone from bull testes, and Adolf Butenandt simultaneously synthesized it from cholesterol [2]. Within two years, pharmaceutical testosterone propionate was available by intramuscular injection.

Early Clinical Use

Testosterone propionate required injections every two to three days because of its short half-life. Patients with Kallmann syndrome (a genetic cause of GnRH deficiency) and other forms of hypogonadotropic hypogonadism received these injections primarily to restore libido, bone density, and secondary sex characteristics. Fertility was not on the clinical agenda for most practitioners of that era.

World War II slowed the international dissemination of endocrine research, but by 1945 military physicians in the United States had access to testosterone propionate through Army formularies. Dosing was empirical: 25 mg every two to three days was a common starting point, with no randomized data to support it.

What This Era Got Right and Wrong

Practitioners correctly identified that androgen replacement reversed symptoms. They did not yet recognize that exogenous testosterone suppresses the hypothalamic-pituitary axis, foreclosing future fertility. That mechanistic understanding would not fully emerge until the 1970s [3].

The 1950s and 1960s: Gonadotropin Therapy Arrives

Human chorionic gonadotropin (hCG), which mimics LH action at testicular Leydig cells, had been extracted from pregnant women's urine since the 1920s. Its clinical application in male hypogonadism was systematized by the early 1950s.

hCG Monotherapy

HCG injections (typically 1,000-2,000 IU intramuscularly two to three times per week) could stimulate testicular testosterone production in men whose testes retained function. For secondary hypogonadism, this was the first treatment that did not directly suppress the pituitary axis. Testosterone levels rose, and in some men, spermatogenesis partially resumed [4].

The limitation was that hCG alone rarely fully restored sperm counts in men with severe hypogonadotropic hypogonadism, because FSH is also required for Sertoli cell support of sperm maturation.

Addition of Exogenous FSH

Human menopausal gonadotropin (hMG, marketed as Pergonal), derived from the urine of postmenopausal women and containing both LH and FSH activity, became available in Europe in 1957 and received FDA approval for human use in the United States in 1969 [5]. Combining hCG with hMG gave clinicians a way to provide both gonadotropin signals simultaneously.

A landmark case series from Gemzell and Roos published in 1966 documented successful induction of spermatogenesis in men with pituitary failure using hMG plus hCG, establishing the combination as the standard fertility-directed protocol for secondary hypogonadism for the next two decades [4].

Testosterone Enanthate Enters the Market

Longer-acting testosterone esters, particularly testosterone enanthate (approved for use in the 1950s) and testosterone cypionate, reduced injection frequency to every one to two weeks. These became the dominant testosterone replacement options globally and remain widely prescribed today. A 2020 analysis in JAMA Internal Medicine documented that testosterone cypionate accounts for approximately 65% of all TRT prescriptions in the United States [6].

The 1970s: Axis Suppression Recognized, Oral Androgens Introduced

The 1970s produced two important developments. First, radioimmunoassay technology allowed routine measurement of LH, FSH, and testosterone in clinical laboratories, finally making the diagnostic distinction between primary and secondary hypogonadism reliable. Second, 17-alpha-alkylated oral androgens (methyltestosterone, oxymetholone) were already on the market, and mounting evidence of their hepatotoxicity led the FDA to restrict their indications [7].

Understanding Negative Feedback

Research groups including Bremner, Paulsen, and colleagues at the University of Washington published studies in the early 1970s demonstrating that exogenous testosterone suppresses LH secretion through negative feedback at both the hypothalamus and pituitary [3]. This confirmed what many clinicians suspected: testosterone therapy was incompatible with fertility preservation in men who retained gonadotropin-responsive testes.

This insight was clinically significant. Physicians treating young men with Kallmann syndrome or idiopathic hypogonadotropic hypogonadism (IHH) had to choose between androgen replacement for symptom control and gonadotropin therapy for fertility. No middle path existed yet.

The 1980s: Pulsatile GnRH Pump Therapy

The most physiologically elegant advance of the 20th century for secondary hypogonadism arrived when researchers confirmed that GnRH must be delivered in pulses, not continuously, to stimulate normal pituitary function. Continuous GnRH actually downregulates pituitary GnRH receptors, which is why GnRH agonists like leuprolide suppress testosterone in prostate cancer treatment.

The Leyendecker and Knobil Contributions

Ernst Knobil's primate studies in the late 1970s established that pulsatile GnRH (one pulse every 60-90 minutes) was required for normal LH and FSH release [8]. Leyendecker and colleagues then translated this to human therapy. By 1980, portable infusion pumps delivering subcutaneous or intravenous GnRH pulses at physiologic intervals could restore normal gonadotropin profiles in both men and women with hypothalamic hypogonadism.

The FDA cleared GnRH (gonadorelin) for pulsatile pump use in the early 1980s. In men with hypothalamic-origin secondary hypogonadism, pulsatile GnRH therapy could restore normal testosterone, LH, FSH, and sperm production simultaneously, something no prior treatment achieved in a single agent.

Practical Limitations of GnRH Pump Therapy

The pump was expensive, required dedicated nursing support, and risked infection at infusion sites. Compliance was a significant problem. GnRH peptides also degraded quickly, requiring refrigerated cartridges. For men seeking only androgen replacement without fertility, the pump offered no advantage over a simple testosterone injection. Its use remained confined largely to academic referral centers and to patients actively pursuing conception [9].

The 1990s: Transdermal Testosterone and Refined Gonadotropin Products

The 1990s brought testosterone delivery innovation. The FDA approved the first testosterone transdermal patch (Testoderm, for scrotal application) in 1993, followed by non-scrotal patches (Androderm) in 1995, and testosterone gel (AndroGel) in 2000 [10]. These formulations produced steadier serum levels compared to the peak-and-trough pharmacokinetics of biweekly injections.

Why Transdermal Mattered for Secondary Hypogonadism

Men with secondary hypogonadism are often younger than those with primary hypogonadism and may be more sensitive to the quality-of-life effects of testosterone fluctuations. Transdermal delivery reduced mood swings and energy crashes between injections, a complaint common in the injection era. Serum levels with AndroGel 1% (5 g/day) approximate mid-normal range (400-700 ng/dL) in most men [10].

Recombinant FSH (follitropin alfa, Gonal-F) and recombinant LH received European approval in the late 1990s, replacing urine-derived hMG for fertility-directed therapy. Recombinant products carried lower batch-to-batch variability and eliminated theoretical viral transmission risk from urine-pooled preparations [4].

The 2000s: Off-Label SERMs and the Clomiphene Era

Selective estrogen receptor modulators (SERMs), developed initially for breast cancer and female infertility, gained off-label traction in men with secondary hypogonadism after 2000. Clomiphene citrate (Clomid) blocks estrogen receptors at the hypothalamus and pituitary, reducing negative feedback and increasing endogenous GnRH, LH, and FSH secretion.

Clomiphene Citrate Evidence

A prospective study by Shabsigh et al. (2005, N=36) found that clomiphene citrate 25-50 mg every other day raised mean testosterone from 247 ng/dL to 610 ng/dL over four to six weeks, without suppressing sperm production [11]. This made it uniquely attractive for men with secondary hypogonadism who wanted both symptomatic improvement and preserved fertility.

Clomiphene remains off-label for male hypogonadism in the United States as of 2025. The FDA has not approved it for this indication, but it appears in the Endocrine Society guideline as an option in specific clinical scenarios [1]. Prescribing physicians are responsible for informed consent regarding its off-label status.

Anastrozole and Aromatase Inhibitor Misuse

The same decade saw aromatase inhibitors (anastrozole, letrozole) prescribed off-label to obese men with secondary hypogonadism, theorizing that excess peripheral aromatization of testosterone to estradiol was suppressing their pituitary output. The evidence base was thin. The Endocrine Society guideline explicitly notes inadequate data to recommend routine aromatase inhibitor use for hypogonadism outside clinical trials [1].

The 2010s: Testosterone Pellets, Subcutaneous Injections, and the FDA Label Controversy

Testosterone pellets (Testopel), implanted subcutaneously every three to six months, had existed since the 1940s in some markets. Their use expanded substantially in the United States after 2010, driven by direct-to-consumer marketing and cash-pay clinic models.

The 2014 FDA Safety Communication

In January 2014, the FDA issued a safety communication requiring manufacturers to add a warning about possible increased cardiovascular risk associated with testosterone products [12]. This followed observational studies, including Vigen et al. In JAMA (2013, N=8,709), which reported a higher rate of adverse cardiovascular events in men prescribed testosterone after coronary angiography [13].

The signal prompted significant clinical debate. Men with secondary hypogonadism who had been on stable TRT for years were suddenly faced with prescribers reconsidering their therapy. The American Association of Clinical Endocrinology and multiple urology societies countered that the observational data had confounders and that the cardiovascular risk was not established.

The TRAVERSE Trial Resolution

The TRAVERSE trial (N=5,246), reported in the New England Journal of Medicine in 2023, enrolled middle-aged and older men with hypogonadism and pre-existing cardiovascular disease or high cardiovascular risk [14]. Men received testosterone gel 1.62% or placebo. At a median follow-up of 33 months, major adverse cardiovascular events occurred in 7.0% of the testosterone group versus 7.3% of placebo (hazard ratio 0.96; 95% CI 0.78-1.17), effectively ruling out a large cardiovascular harm signal for men meeting guideline criteria. The trial also found a modestly higher rate of atrial fibrillation, pulmonary embolism, and acute kidney injury in the testosterone group, findings that continue to inform prescribing labels.

The 2020s: Subcutaneous Testosterone, Digital Prescribing, and Combination Protocols

The current decade has seen subcutaneous testosterone cypionate injections (25-50 mg weekly or twice weekly) gain clinical favor for secondary hypogonadism management. Compared to the traditional 200 mg intramuscular dose every two weeks, smaller and more frequent subcutaneous doses produce steadier serum testosterone with lower hematocrit elevation, a practical advantage given that erythrocytosis (hematocrit above 54%) is the most common adverse effect requiring dose reduction under current guidelines [1].

The Modern Combination Protocol for Fertility

Men with secondary hypogonadism who are currently on TRT and wish to conceive now have a documented transition protocol. Stopping testosterone and starting hCG (typically 1,500-3,000 IU three times weekly) restores intratesticular testosterone. Adding recombinant FSH (75-150 IU three times weekly) once LH analogue therapy is established can further support spermatogenesis. Recovery of sperm production typically requires three to twelve months, longer in men who have used testosterone for more than two years [4].

The Endocrine Society guideline recommends this gonadotropin-based approach for men with secondary hypogonadism seeking fertility and characterizes it as a practice with good evidence [1].

Telehealth Prescribing and the HealthRX Model

Telehealth platforms expanded access to TRT dramatically after 2020, when the DEA temporarily allowed controlled substance prescribing via telemedicine without in-person visits. For secondary hypogonadism, where the root cause (pituitary adenoma, medication effect, obesity, opioid use) must be identified before lifelong testosterone is initiated, this expanded access carries both benefit and risk. The Endocrine Society guideline specifies that MRI of the pituitary is indicated in men with a serum prolactin above the upper normal limit or LH below 1.0 IU/L, to exclude a pituitary tumor [1].

HealthRX protocols require baseline LH, FSH, prolactin, and pituitary MRI when clinically indicated before initiating therapy. This is not simply administrative: a man with a prolactinoma causing secondary hypogonadism needs dopamine agonist therapy (cabergoline 0.25-0.5 mg twice weekly), not testosterone, as first-line treatment [15].

Decade-by-Decade Summary of Milestones

| Decade | Key Development | Clinical Impact | |--------|----------------|-----------------| | 1930s | Testosterone propionate injection | First androgen replacement | | 1950s | hCG therapy; testosterone enanthate | Fertility-directed option; longer dosing intervals | | 1960s | hMG (Pergonal) approved; gonadotropin assays | Combined gonadotropin therapy; reliable subtype diagnosis | | 1970s | Radioimmunoassay routine; axis suppression defined | Fertility vs. Replacement decision clarified | | 1980s | Pulsatile GnRH pump | Physiologic axis restoration possible | | 1990s | Transdermal patches; recombinant gonadotropins | Steadier levels; safer FSH products | | 2000s | Clomiphene off-label use | Fertility-preserving androgen boost | | 2010s | FDA cardiovascular warning; TRAVERSE initiated | Risk-benefit reappraisal | | 2020s | Subcutaneous dosing; telehealth prescribing | Access and convenience expanded |

Current Guideline Recommendations (2018 Endocrine Society)

The 2018 Endocrine Society Clinical Practice Guideline on testosterone therapy in men with hypogonadism provides the most authoritative current framework [1]. Key positions relevant to secondary hypogonadism include:

Diagnosis

Confirm two morning testosterone measurements below 300 ng/dL with symptoms. Measure LH and FSH to confirm the secondary pattern. Screen for reversible causes: hyperprolactinemia, opioid use, glucocorticoid excess, hemochromatosis, and sleep apnea.

Treatment Selection

For men not desiring fertility: testosterone replacement (injection, gel, or pellet) is appropriate. For men desiring fertility: gonadotropin therapy (hCG with or without FSH) or pulsatile GnRH if a hypothalamic cause is confirmed. Clomiphene citrate may be considered as an off-label alternative when fertility preservation is a goal and gonadotropin therapy is not available.

Monitoring

Measure hematocrit at baseline and at three to six months. Target testosterone mid-normal range (400-700 ng/dL). Withhold or reduce dose if hematocrit exceeds 54% [1].

What Has Not Changed in 90 Years

The core therapeutic principle has not shifted since 1935: secondary hypogonadism requires replacement of the missing hormonal signal. What has changed is the precision of that replacement. Early practitioners delivered pharmacologic surges of testosterone; modern subcutaneous protocols mimic circadian testosterone rhythms. Early gonadotropin therapy used unpurified urinary extracts; today's protocols use recombinant single-molecule preparations with documented batch consistency.

The fertility-versus-replacement tension, identified explicitly in the 1970s when axis suppression was confirmed, still shapes every initial consultation for a young man with newly diagnosed hypogonadotropic hypogonadism. A 25-year-old man started on testosterone cypionate today faces the same consequence as one started in 1975: his spermatogenesis will likely cease within weeks [3].