Brief Answer:
Yes synthroid will, if hypothyroid is the cause

Detailed Answer:
Thank you for asking!
Erectile dysfunctions has many causes , hypothyroidism is one of them.Now using synthroid might help indirectly by helping the thyroid levels if that is causing the performance issue.
To assess better what is causing the ED in your case we need a thorough history regarding
Sexual history
Medical history
Psychosocial history
followed by physical examination focussing on
Blood pressure
Peripheral pulses
Sensation
Status of the genitalia and prostate
Size and texture of the testes
Presence of the epididymis and vas deferens
Abnormalities of the penis (eg, hypospadias, Peyronie plaques)
Then some labs to be run for sorting out underlying cause .following labs will be needed
Evaluation of hormonal status (testosterone, serum hormone–binding globulin, luteinizing hormone [LH], prolactin, thyroid-stimulating hormone [TSH]) – Note that the XXXXXXX College of Physicians (ACP) does not recommend for or against routine use of hormonal blood tests or hormonal treatment in ED patients
Screening blood studies (hemoglobin A1c, serum chemistry panel, lipid profile)
Prostate-specific antigen levels, if the patient is a candidate for prostate cancer screening (controversial)
Urinalysis
SOme functional tests like
Direct injection of prostaglandin E1 (PGE1; alprostadil) into the corpora cavernosa
Biothesiometry – Infrequently indicated
Nocturnal penile tumescence testing – Once frequently performed, this is rarely used in current practice, though it can be helpful when the diagnosis is in doubt
Formal neurologic testing – Not needed in the vast majority of ED patients, though it may offer some benefit to patients with a history of central nervous system problems, peripheral neuropathy, diabetes, or penile sensory deficit
Some imaging studies like
Ultrasonography of the penis (to assess vascular function within the penis)
Ultrasonography of the testes (to help disclose abnormalities in the testes and epididymides; rarely indicated)
Transrectal ultrasonography (to disclose abnormalities in the prostate and pelvis that may interfere with erectile function)
Angiography (in patients who are potential candidates for vascular surgery)
Once we do all these labs we will know for sure what is causing your performance issues. The management is easy and will focus on
Sexual counseling, if no organic causes can be found for the dysfunction
Oral medications
Injected, implanted, or topically applied medications
External vacuum and constriction devices
Surgery
following agents are used
Sildenafil
Vardenafil
Tadalafil
Avanafil
Alprostadil (most common)
Phentolamine
Papaverine
External devices that may be used include the following:

Vacuum devices to draw blood into the penis
Constriction devices placed at the base of the penis to maintain erection

some surgical options for ED are
Revascularization (rarely indicated)
Surgical elimination of venous outflow (rarely indicated)
Placement of penile implant (semirigid or malleable rod implant, fully inflatable implant, or self-contained inflatable unitary implant) – Once the only effective therapy for men with organic ED, this is the last option considered in current practice

Last but not the least is management of diet and lifestyle modifications and
Optimal management of diabetes, heart disease, and hypertension
Lifestyle modifications to improve vascular function (eg, not smoking, maintaining ideal body weight, and engaging in regular exercise).
I hope it helps. Get to a sex therapist and let him decide what is best for you.
I hope you see it in a right perspective. Take good care of yourself and don't forget to close the discussion please.
Regards
S Khan

---