From the test results it appears that your husband has an autoimmune dysfunction called Hashimoto's Thyroiditis. With Hashi's the autoimmune system erroneously identifies the thyroid gland as foreign to the body and produces antibodies to attack and eventually destroy the gland. As this proceeds, the output of the gland diminishes, and the Pituitary produces more TSH to try and stimulate more output from the thyroid gland. The solution is to take thyroid mediation adequate to relieve hypothyroid symptoms, without creating symptoms of hyperthyroidism. Med dose adjustment must be based primarily on symptoms not blood test results and never based on TSH which is apparently what his doctor is doing.
The 100 mcg of T4 is nowhere near a full daily replacement amount of thyroid medication, which he needs. The average thyroid gland produces about 94-110 mcg of T4 daily, along with about 10-22 mcg of T3. In addition thyroid med is only about 80% absorbed, so the dose has to be higher to account for the loss. In addition many hypo patients taking T4 find that their body does not adequately convert T4 to T3. Since FT3 is the "gasoline" which runs your engine (your body), it is important that Free T3 should be in the upper half of its range, in order to relieve hypo symptoms. This often requires the addition of T3 to the patient's med dosage.
Most doctors think that TSH tells them all they need to know about a patient's thyroid status. This is totally wrong. TSH is useful as a diagnostic only when at extreme levels. After diagnosis, treatment with thyroid med changes the equilibrium among TSH, Free T4 and Free T3 such that TSH is typically suppressed below range when taking adequate thyroid medication. TSH cannot be used to determine med dosage because it has only a weak correlation with the actual thyroid hormones FT4 and FT3, and a negligible correlation with symptoms. A good thyroid doctor will diagnose and treat a hypothyroid patient clinically, based on symptoms, supported with expanded testing that includes Free T4, Free T3, initially Reverse T3, cortisol, Vitamin D, B12 and ferritin. Men are not as likely to be low in ferritin but it should be tested to make sure. D should be at least 50 ng/mL, B12 in the upper part of its range, and ferritin should be at least 100.
The chance of the Endo being a good thyroid doctor is slim. Most specialize in diabetes, not thyroid. Many have the "Immaculate TSH Belief" and only pay attention to that for diagnosis and treatment. That doesn't work. You need a good thyroid doctor that will treat clinically by adjusting your husband's FT4 and FT3 levels as required to relieve hypo symptoms. If you are interested, we can try to help locate a good thyroid doctor in your area.
As an alternative you can click on my name and then scroll down to my Journal and there you will find an Overview of a paper on "Diagnosis and Treatment of Hypothyroidism: A Patient's Perspective". I highly recommend reading at least the Overview and then you might try to influence the current doctor by giving the doctor a copy and asking him to consider clinical treatment for your husband rather than just based on TSH level.
Sending you a PM with info. To access, click on your name and then from your personal page click on messages.