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Q7 - Testosterone, Pituitary Feedback, and Body Mass

Theoretical B Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Endocrine System Physiology

Variation in testosterone levels has major effects on general male physiology. Concentration of testosterone was measured in blood plasma from five groups of men (Fig.).

A, plasma level of testosterone in: I, Males 16-43 years old; II, Males 44-92 years; III, Males with underdeveloped pituitary glands; IV, Males with removed testes; and V, Males after treatment with injections of estrogen for some time. Each dot represents an individual, and the horizontal bars are group averages; B, plasma testosterone level in men as a function of body mass index (T = 23.94 – 0.26 BMI) (from Zumoff et al. 1990).

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. Males-IV have reduced testosterone level due to negative feed-back regulation
B. Males-IV have a high LH concentration compared to Males-I
C. Estrogen injections in males lead to very low concentrations of LH
D. Even mild obesity (25<BMI < 30) might be much more important to testosterone level than higher age (> 43 years)
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Question reproduced from IBO 2015, Theoretical Exam B, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)