The purpose of this study is to assess the change in 24-hour ambulatory blood pressure monitoring (ABPM) between baseline (Day 0) and Day 120 following 4 months of testosterone therapy with Natesto.

Inclusion Criteria:

• Voluntarily sign and date the study consent form(s) which have been approved by an Institutional Review Board (IRB). Written consent must be obtained prior to the initiation of any study procedures.
• Male between 18 and 80 years of age, inclusive, with documented onset of hypogonadism prior to age 65.
• Serum total testosterone < 300 ng/dL based on 2 consecutive blood samples obtained no greater than 1-4 weeks apart between 6 and 10 AM following an appropriate washout of current androgen replacement therapy if not testosterone naive. Historical values from the past 6 months may be used.
• Testosterone Therapy naive, OR off any testosterone therapy for at least 4 months OR agree to a 4-month washout of current testosterone therapy prior to entry at Visit 1.
• Average office blood pressure measurement <140 millimetre of mercury (mmHg) SBP -AND- <90 mmHg DBP.
• If the participant is on an antihypertensive regimen, he has been on it for at least 4 weeks.
• Judged to be in good general health as determined by the principal investigator based upon the results of a medical history, physical examination, vital signs, laboratory profile and a 12-lead electrocardiogram (ECG).

Exclusion Criteria:

• History of significant sensitivity or allergy to androgens, castor oil or product excipients.

• Clinically significant findings in the pre-study examinations including abnormal breast examination requiring follow-up, an abnormal ECG.

• Abnormal prostate digital rectal examination (DRE) with palpable nodule(s) or International Prostate Symptom Score (I-PSS) score > 19 points.

• Body mass index (BMI) ≥ 35 kg/m^2.

• Clinically significant abnormal laboratory value, in the opinion of the investigator, in serum chemistry, hematology, or urinalysis including but not limited to:

  • Prostate specific antigen (PSA) > 4 ng/mL
  • Hematocrit < 35% or > 50%
  • Baseline hemoglobin > 16 g/dL
  • Hemoglobin A1C (HbA1C) > 9.0%
  • Estimated glomerular filtration rate (eGFR) <45

• History of seizures or convulsions, including febrile, alcohol or drug withdrawal seizures.

• History of any clinically significant illness, infection, or surgical procedure within 4 weeks prior to study drug administration except for diabetes, or renal disease.

• History of stroke or myocardial infarction within the past 5 years.

• History of, or current or suspected, prostate or breast cancer.

• History of diagnosed, severe, untreated, obstructive sleep apnea.

• History of abuse of alcohol or any drug substance in the opinion of the investigator within the previous 2 years.

• Currently using tobacco, e-cigarettes or other nicotine containing products.

• History of nasal disorders such as nasal surgery; nasal trauma resulting in nasal fracture within the previous 6 months or nasal fracture that caused a deviated anterior nasal septum; or sinus surgery or sinus disease.

• Receipt of any investigational product within 4 weeks of study start.

• Inability to understand and provide written informed consent for the study.

• Considered by the investigator or the sponsor-designated physician, for any reason, as an unsuitable candidate to receive Natesto.

• Participants working night-shifts.

• Participants performing strenuous manual labor while wearing the ABPM monitor.

• Participants with chronic atrial fibrillation (interferes with the ability to obtain precise ambulatory recordings).