info regarding levothyroxine and bone loss

The thing about osteoporosis is that it is “silent” . Not pain until something breaks. I have several friends that have had knee replacement, but they don’t have osteoporosis. Me, I have severe osteoporosis, but no joint or bone pain.

Bone loss due to levothyroxine is much more pronounced when the levothyroxine dose is too high, underscores the importance of regular lab checks.

What dose is considered too high? I have been taking 50mgs a day for over 20 years and now have muscle mass loss bad. I see my doc next week and want to know if I can take less. All of my lab numbers have been in the good range back to 2020. Thanks

The dose of levothyroxine is too high if the TSH is in the low range. If your numbers consistently are in the normal range, you are on the correct dose:)

I've just been alerted that Levothyroxine, which I've taken for years, can affect osteoporosis, which I've also had for years. Although I've run through numerous medications: Fosamax, Prolia, and Tymlos to name a few, doctors can't figure out why I haven't improved bone density. Plan to ask doc asap,

@shirley74 my levothyroxine is 75 MCG and I split one and take the half pills 2x per week…I have OP…. But am aware that cancer treatments can also affect bones…docs holding off on OP meds so I can use my cancer recovery energy to do very good PT, exercises, walking— plus good supplements and a few dietary adjustments… levothyroxine is a very important med and people have to be careful what other meds work okay with it…timing of supplements is important , no calcium supplements within 4 hours of taking levothyroxine.

I haven’t read the studies above. I am a disabled healthcare professional. Even 30 years ago, when I was in med school, it was known that too much levothyroxine, as evidenced by a low TSH would cause osteoporosis. That is why we are so meticulous in checking thyroid lanpbs regularly. Are you positing that simply being on levothyroxine, even within the normal therapeutic window, will cause osteoporosis?

From internet search Mechanism of action of T3 and T4 on bones:
T3 and T4 influence bone cells (chondrocytes, osteoblasts, osteoclasts) by
binding to nuclear receptors (mainly TRα1) to regulate gene expression, impacting development, growth, and remodeling; they stimulate bone growth during childhood but accelerate resorption in adults, leading to net bone loss and osteoporosis in excess, affecting matrix proteins, growth factors (like IGF-1, Wnt), and remodeling enzymes through complex signaling pathways like BMP and Wnt.
Mechanism of Action
Cellular Entry & Receptor Binding: T4 is converted to the more active T3 in tissues; T3 enters bone cells (osteoblasts, osteoclasts, chondrocytes) and binds to thyroid hormone receptors (TRs) in the nucleus, primarily TRα1.
Gene Regulation: This T3-receptor complex then modulates gene transcription, acting as a switch to turn genes on or off, affecting protein synthesis and cell function.
Effects on Specific Bone Cells
Chondrocytes (Cartilage Cells): Essential for growth plate development, T3 regulates chondrocyte differentiation, proliferation, and maturation, coordinating linear bone growth.
Osteoblasts (Bone-Forming Cells): T3 stimulates osteoblast activity, collagen synthesis, alkaline phosphatase (ALP), and bone matrix proteins (osteopontin, osteocalcin).
Osteoclasts (Bone-Resorbing Cells): T3 directly promotes bone resorption, increasing osteoclast activity and the expression of enzymes like matrix metalloproteinases (MMPs) that break down bone.
Net Effect on Bone
Childhood: Stimulates growth and development (anabolic).
Adulthood (Excess): Accelerates bone remodeling, leading to increased resorption over formation (catabolic), causing net bone loss and osteoporosis

@laura1970 hi, not a doc or scientist, just a person trying to sort out how to deal with OP …but the correlation between levothyroxine and bones seems fairly clear, having something to do with calcium absorption…probably a good idea for docs/patients to consider calcium supplements when prescribing/taking levothyroxine, taking care with timing.

I have taken Synthroid since 1988-my bones never adversely affected. I think its important to look at total health of person before assuming any med is a cause of a condition.