I recall reading somewhere that coconut oil (unrefined) in food can help with this. For a baby not yet on solid foods, putting some on the nipple just before nursing might help.
I battled with constipation for most of my life (I’m now 66), knew I was hypothyroid at least 30 years ago, was diagnosed with Hashimoto’s about 10 years ago. I tried high-fibre eating, low-fibre eating (after reading Fiber Menace). I’ve been taking Thyrolax for at least 4.5 years (includes bovine glandular). I was gluten free for several years, but as of last October I’m eating it again. However, about 4 years ago, I followed some advice from Matt (which he can clarify if I’m missing something here). Basically it’s this: nothing but fruit for a week, add some vegetables and a bit of fat the second week, gradually add protein the following week. Unless I’m travelling, and my schedule is off, I usually have a bowel movement on average 3 times a day. Lately, I’ve been eating more fruit than I used to, very little grain (not whole grain) food, and a raw carrot most days.