A woman charts her cycle using cervical mucus observations. Around ovulation her mucus becomes clear, stretchy and forms a thread longer than 6 cm before breaking. This property (spinnbarkeit) results from which hormonal effect?

• A Progesterone increasing mucin cross-linking
• B FSH stimulating cervical gland hyperplasia
• C LH causing desquamation of cervical epithelial cells
• D Estrogen increasing water and electrolyte content of cervical mucus ✓

Explanation

High preovulatory estradiol makes cervical mucus abundant, thin, watery and alkaline, with low cell content, allowing a long stretchable thread (spinnbarkeit) and channelling sperm ascent. After ovulation, progesterone makes mucus thick, cellular and inelastic, so ferning and spinnbarkeit disappear. Progesterone thickens rather than thins mucus, ruling out A. LH does not act on cervical epithelium this way, and the change reflects hydration of existing glands rather than FSH-driven hyperplasia, excluding C and B.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.