When should FSH (Follicle-Stimulating Hormone) and LH (Luteinizing Hormone) levels be measured in the menstrual cycle for suspected pituitary adenomas?

FSH and LH Measurement Timing for Pituitary Adenoma Evaluation

For suspected pituitary adenomas, FSH and LH should be measured between days 3-6 of the menstrual cycle, with blood samples taken in the morning (around 8 am) and averaged from three estimations taken 20 minutes apart. 1

Optimal Timing for Hormone Measurement

• FSH and LH should be measured during the early follicular phase (days 3-6) of the menstrual cycle for most accurate assessment of pituitary function 1, 2
• Morning measurements (around 8 am) are preferred to account for diurnal variations in hormone levels 1
• For increased accuracy, consider calculating an average based on three estimations taken 20 minutes apart 1
• In amenorrheic women, measurements can be taken at any time but should be interpreted in the context of other hormonal parameters 2

Comprehensive Hormone Panel for Pituitary Adenoma Evaluation

• For suspected pituitary adenomas, a complete hormone panel should include:
  • FSH and LH (early follicular phase) 1
  • Prolactin (morning resting levels, not postictal) 1
  • Thyroid function tests (TSH, free T4) 1
  • Adrenal function (ACTH, cortisol or 1 mcg cosyntropin stimulation test) 1
  • Gonadal hormones (testosterone in men, estradiol in women) 1
  • IGF-1 to rule out clinically silent GH-secreting tumors 1

Interpretation of Results

• An LH/FSH ratio >2 may indicate polycystic ovary syndrome, which can be associated with pituitary disorders 1
• FSH >35 IU/L and LH >11 IU/L may indicate primary ovarian failure rather than pituitary pathology 1
• LH <7 IU/mL may suggest pituitary dysfunction 1
• In pituitary adenomas, the most commonly affected pituitary axis is the GH axis (61-100%), followed by hypogonadism (36-96%), adrenal insufficiency (17-62%), and central hypothyroidism (8-81%) 1

Special Considerations for Different Types of Pituitary Adenomas

• For non-functioning pituitary adenomas (NFPAs):

  • Routine endocrine evaluation of all anterior pituitary axes is recommended to assess for hypopituitarism 1
  • Routine prolactin testing is essential to rule out hypersecretion that might not be clinically suspected 1
  • IGF-1 evaluation is recommended to rule out growth hormone hypersecretion 1

• For suspected hypophysitis (pituitary inflammation):

  • Morning measurements of TSH, free T4, ACTH, cortisol, gonadal hormones, FSH, and LH are recommended 1
  • MRI of the sella with pituitary cuts should be performed prior to steroid administration 1

Common Pitfalls to Avoid

• Measuring hormone levels during use of hormonal contraceptives or hormone replacement therapy may mask underlying abnormalities 2
• Failing to consider diurnal variations in hormone levels can lead to inaccurate results 2
• Not accounting for the phase of the menstrual cycle when interpreting results can lead to misdiagnosis 3
• Overlooking the possibility of FSH-secreting adenomas, which may not respond normally to stimulation or suppression tests 4, 5

Follow-up Recommendations

• For patients with confirmed pituitary adenomas, regular monitoring of pituitary function is recommended 1
• Multidisciplinary discussion at both local and national levels is key for optimal management of pituitary adenomas 1
• Patients with adrenal insufficiency due to pituitary dysfunction should be instructed to obtain and carry a medical alert bracelet 1

Remember that pituitary adenomas in children and young people require special consideration as they often present differently than in adults and may have a more aggressive nature with increased potential for familial or genetic etiology 1.