Go to JCI Insight
  • About
  • Editors
  • Consulting Editors
  • For authors
  • Publication ethics
  • Publication alerts by email
  • Advertising
  • Job board
  • Contact
  • Clinical Research and Public Health
  • Current issue
  • Past issues
  • By specialty
    • COVID-19
    • Cardiology
    • Gastroenterology
    • Immunology
    • Metabolism
    • Nephrology
    • Neuroscience
    • Oncology
    • Pulmonology
    • Vascular biology
    • All ...
  • Videos
    • Conversations with Giants in Medicine
    • Video Abstracts
  • Reviews
    • View all reviews ...
    • Pancreatic Cancer (Jul 2025)
    • Complement Biology and Therapeutics (May 2025)
    • Evolving insights into MASLD and MASH pathogenesis and treatment (Apr 2025)
    • Microbiome in Health and Disease (Feb 2025)
    • Substance Use Disorders (Oct 2024)
    • Clonal Hematopoiesis (Oct 2024)
    • Sex Differences in Medicine (Sep 2024)
    • View all review series ...
  • Viewpoint
  • Collections
    • In-Press Preview
    • Clinical Research and Public Health
    • Research Letters
    • Letters to the Editor
    • Editorials
    • Commentaries
    • Editor's notes
    • Reviews
    • Viewpoints
    • 100th anniversary
    • Top read articles

  • Current issue
  • Past issues
  • Specialties
  • Reviews
  • Review series
  • Conversations with Giants in Medicine
  • Video Abstracts
  • In-Press Preview
  • Clinical Research and Public Health
  • Research Letters
  • Letters to the Editor
  • Editorials
  • Commentaries
  • Editor's notes
  • Reviews
  • Viewpoints
  • 100th anniversary
  • Top read articles
  • About
  • Editors
  • Consulting Editors
  • For authors
  • Publication ethics
  • Publication alerts by email
  • Advertising
  • Job board
  • Contact
The puzzle of lactational bone physiology: osteocytes masquerade as osteoclasts and osteoblasts
Brittany A. Ryan, Christopher S. Kovacs
Brittany A. Ryan, Christopher S. Kovacs
Published June 24, 2019
Citation Information: J Clin Invest. 2019;129(8):3041-3044. https://doi.org/10.1172/JCI130640.
View: Text | PDF
Commentary Article has an altmetric score of 4

The puzzle of lactational bone physiology: osteocytes masquerade as osteoclasts and osteoblasts

  • Text
  • PDF
Abstract

Lactation is a unique period in which the maternal skeleton acts as a storehouse to provide substantial calcium to milk. Women who exclusively breastfeed lose an average of 210 mg of calcium per day, which doubles or triples with twins and triplets. Data from rodent and clinical studies are consistent with skeletal calcium being released to provide much of the calcium needed for milk production. This is programmed to occur independently of dietary calcium intake or intestinal calcium absorption, which remains at the prepregnant rate in breastfeeding women. After weaning, the skeleton is restored to its prior mineralization and strength, but the factors that regulate this remain to be elucidated.

Authors

Brittany A. Ryan, Christopher S. Kovacs

×

Figure 1

Breast-brain-bone circuit controls skeletal resorption during lactation.

Options: View larger image (or click on image) Download as PowerPoint
Breast-brain-bone circuit controls skeletal resorption during lactation....
Suckling and prolactin (PRL) both inhibit the hypothalamic gonadotropin-releasing hormone (GnRH) pulse center, which in turn suppresses the gonadotropins (luteinizing hormone [LH] and follicle-stimulating hormone [FSH]), leading to low levels of the ovarian sex steroids (estradiol [E2] and progesterone [PROG]). PRL may also have direct effects on its receptor in bone cells. PTHrP production and release from the breasts is stimulated by suckling, PRL, low estradiol, and the calcium receptor. PTHrP enters the bloodstream and combines with systemically low estradiol levels to markedly upregulate bone resorption and (at least in rodents) osteocytic osteolysis. These activities release calcium and phosphate, which reach the breast ducts and are actively pumped into the breast milk. PTHrP also passes into milk at high concentrations, but whether swallowed PTHrP plays a role in regulating calcium physiology of the neonate is uncertain. In addition to stimulating milk ejection, oxytocin (OT) may directly affect osteoblast and osteoclast function. Calcitonin may inhibit skeletal responsiveness to PTHrP and low estradiol. The inset at the top right depicts a cross-section of cortical and trabecular bone from a vertebral body at a micron level of magnification. At the onset of lactation, multinucleated osteoclasts and osteocytes are poised to resorb mineral from bone. The inset at the bottom right depicts progressive trabecular thinning by osteoclasts, whereas osteocytic osteolysis leads to a progressive increase in the lacunar area. The two processes contribute to increased cortical porosity.

Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)

Sign up for email alerts

Posted by 4 X users
On 3 Facebook pages
25 readers on Mendeley
See more details