If she’s still symptomatic despite supplementing with T4, she’s likely not converting it well to free T3. Have her check her iron/ferritin, RBC zinc, vitamin A, selenium levels for starters. What’s her stress level? Any other sign of inflammation in her body? This will cause thyroid hormone to get converted to the inactive Reverse T3 as well and lead to these symptoms.

Also, what’s her diet like? Does she eat animal products? Does she suffer from GI symptoms as well that might indicate poor digestion? We need protein and iodine to make thyroid hormone, so working on her diet and ensuring she’s getting in these nutrients through food as a foundation is a good idea.

Hey ,

To be complete you can also ask your sister a few questions to see if her low energy levels are related to her thyroid health. Her medications could still be a problem, but other dynamics at play could be missed by having the focus on the thyroid only.

Here are some other reasons why people can be fatigued and some other symptoms that can result from that. You can explore together with your sister if she might be experiencing some of these other symptoms:

Vitamin B12, folate or B6 deficiency:
• Shortness of breath
• Cold hands & feet (A slow thyroid causes people often to have a cold feeling in the entire body. If she is experiencing this type of coldness, that could ‘mask’ this symptom of course)
• Pale skin
• Tingling sensations in the arms or feet
• A ringing sound in the ear
• Problems with the eyes

Not all symptoms have to be present of course. But she has a few of them, let her also check with her doctor for macrocytic anemia. 

Iron deficiency
• Same symptoms, because an iron deficiency can cause iron deficiency anemia. But in the case of iron deficiency, pale skin is often a more present symptom. You can also take a look at her lips or the mucous membrane behind her lips.
• Restless legs

Vitamin D deficiency:
• Muscle cramps
• pain in bones or back pain
• frequently sick
• Being more depressed in the winter (a slow thyroid can make people depressed as well, so this might not be the most helpful ‘symptom’

Magnesium deficiency
• GERD/Heartburn
• Stiffness in muscles
• Also Muscle cramps
• High blood pressure
• Being irritated/stressed more easily

Insulin resistance
• Need to urinate frequently
• Tired between meals
• Cravings for sweets/sugar after dinner
• Getting angry when hungry (hangry)
• Hard to lose weight as well

It might not be diagnostic, but it can give you some insight if there are other underlying dynamics at play as well.

Good luck!